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While I have generally had OK luck in getting carburetors to run right, I have occasionally had issues with one or another and this is one of those times.

I've had a mild stumble in my 40mm Dells from day one and have tried a bunch of stuff to overcome it - always going up in jet size.  Remember also, that I have converted to horizontal discharge tubes since day one, so I have no comparison to unconverted Dells.  

I reset the float levels per the Dell book a couple of years ago and fixed an issue with the accelerator pump drive and they seemed a tad better, but still stumbled whenever the throttle plates were increased (seemingly at any speed), indicating a transition lean-ness (which was why I always went to progressively larger jets).  I have not yet checked the fuel pump pressure - My pump is a CB Rotary so checking pressure is on the list.

Anyway, everything I have read gives these jet recommendations for Dell 40's:

160 Mains

180 Air Corrections 

60 idles

40 Accelerator Pump

I am currently running:

162 mains

160 Air Correction (per Pat Downs to help with the Horizontal discharge tubes)

70 Idle

70 Accelerator Jets

It definitely needs improvement, so I'm going to go totally back to the stock "out of the box" jets and start all over this afternoon.  If I can get the instructions for the horizontal discharge tubes and can un-do the conversion (I have all the parts but I remember inserting a few lead "BB's" into some passages to close them off and need to drill those out), then I'll pull the carbs and do that on the bench, re-adjust the floats again and so forth.  @Pat Downs Can you help with those instructions or whom should I call?  I can't find my old copy.

Any competent recommendations on how best to proceed would be appreciated.  Like how do I measure my venturiis to see what size they really are?  I'm assuming 40mm but they may be different.

Thanks,  gn

 

 

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I've posted this for two reasons:  1. I'm selfish in that I hope to get some solid info and make these Dells much more drive-able, even if I give up some mid/high end power in the process and (2.) others may be having troubles and might learn a bit about how these (and Weber, too) carbs work and maybe can do a little simple tuning on them, too.  (Didn't one of the Todds on here just go through this??)

All I know is, whatever I have done to "improve" things for the past fifteen years has either made no change at all or made things slightly worse.  That's why I'm going back to basics to see (hopefully) what I've been doing wrong, correct it, get a pair of nice-running Dells and move on to something else I can be OCD about.

I have my first question for @Pat Downs

What was the purpose of inserting the lead plugs in the "idle circuit" (taken from a Hot VWs article).  What would happen if they were removed but I kept the Horizontal discharge tubes?

Last edited by Gordon Nichols

I'd increase the float height a little, should help richen the transition. I don't know how Dells are but Webers have different emulsion tubes, some richen at a lower rpm, some higher. You might try that. F11 and F7 for example richen at different places in the transition.

If none of that works, I'd be inclined to investigate your spark curve. As has been said many times 90% of carb problems are ignition problems.

Gordon Nichols posted:

 

What was the purpose of inserting the lead plugs in the "idle circuit" (taken from a Hot VWs article).  What would happen if they were removed but I kept the Horizontal discharge tubes?

I don't know their purpose but I'll bet they're there for a reason, and taking them out will make it run worse, not better. Or try it and report back what you find... 

Gordon, I'm confused:  Do you have a single Dell 40 or dual Dell 40s.

Since you refer to your "Dells" in the plural, I presume you have dual Dells.  If you have duals, you probably don't have 40mm venturi (I hope).  40 mm vents come on Dell 48s and are way too 'flat sided' for anything but driving WOT to redline between shifts, even on a heavy breathing 2332.  

Remove a vent, it should have the size etched somewhere on it.  If not, measure the inside diameter at its narrowest point.  For around town drive-ability you want vents shaped somewhat like an an hourglass; narrower in the middle, more open at the top and bottom.  You didn't say what engine size you have, but if it is maybe a mildish 2110, then 30-34mm vents sound about right.  The 30mm vents should be crisper buzzing around town.

I learned the hard way, bigger is not better.  On my 2332 I have Dell 48 tri-jets (big mistake), and they originally had 40mm vents (bigger mistake).  Until I choked down to 36mm vents the engine would fall on its face with any throttle input until eventually the rpms got high enough to suck some air through those big straight sided 40mm holes.  It didn't matter how I was jetted, nothing happens with throttle input if the engine is too small to generate enough vacuum in mid-range rpms to accelerate intake air through the vents.  

As far as jetting, I liked the look of your 'by-the-book' jetting better (again, assuming we are talking dual carbs).  It sounds way too rich now, and what lead you to the 70mm accel pump?

 

 

Last edited by RS-60 mark
DannyP posted:

 I don't know how Dells are but Webers have different emulsion tubes, some richen at a lower rpm, some higher.

Danny  --  Dellorto has a similar selection of emulsion tubes, for the same purpose.  And it could be that Gordon somehow ended up with 'specialty' emulsion tubes or tubes that have been alien modified which are causing him problems.

Ok, let’s see.....

Engine is a 2,110, 044 wedge-port heads, match-ported intake manifolds, Engle 120 cam, brand-new MagnaSpark II disti set precisely at 32° and the advance curve checked and set on a Sun Distributor bench.

The carbs are a pair of dual 40mm DRLAs 

I’ll measure the vents tomorrow to see what I’ve got.  Should be interesting, but they are slightly hourglassed.  I suspect that they’re 34’s but we’ll see.

Getting to the larger jets was a long, uneventful story.  Surprisingly, I’ve never seen any black smoke from the exhaust.

Remember, these had long ago been converted to horizontal discharge tubes so I guess they could be called “alien”, but they can certainly make gobs of power.  A little untamed, but lots of power, and I have never encountered anyone else on here or elsewhere running them.  The amount of acceleration “snap” up over 4 grand is always surprising.

What’s important is that I‘m going back to a baseline that is known to work and is drive-able in many other 2,110 engines and begin again from there.  Should be in interesting trip.  

I guess I’m getting less impressed by raw power as I get older.  

Loud mufflers just might be next!

Last edited by Gordon Nichols

The lead plugs block off the air inlet for the idle jets. This allows the idle jet extensions for the update kit to work properly. The theory is to raise the air inlet higher so debris doesn’t find its way into the stock air inlet creating a plugged idle jet. 

  You can always drill out the led plugs and go back to the stock idle jet holders. 

I would remove the discharge tubes and go back to the stock Venturi and booster Venturi. I see no issue leaving the lead plugs in and using the extended idle air jet. 

  If you don’t have your stock parts, I have modified the update kit allowing for a stock 34mm Venturi, keeping the discharge tube. The smaller 34mm Venturi signals the discharge tube harder, eliminating the flat spot

Pat!  Thanks for the info.

I dug in my shop attic and actually found the box of original parts from the 1990's

It pays to forever be a pack-rat, even after three house moves and three states.

I'm going to try installing the original stuff and see how that works out.  At my age, I'm willing to give up a little mid/high "grunt" for more smoothness through the range.

Thanks for the info on the plugs.  Since I've already got the extended idle jet holders (are those the same as "Jet Doctors?) I'll just leave the plugs in place.

I'll post on here how I make out, and thanks, again, for the help!

Gordon

Been too hot to be out in the shop working, but I looked closely at the original Venturiis and they are all 34's.  (You were right - they were stamped with the number).  When I found the original parts up in the attic of my shop I also found the original conversion instructions (Hoo-Ray!) and now feel confident that I can easily reverse the process and go back to stock.

As soon as it gets down below 90F in the shop.......

Hey, just thought of something:  The narrow part of the Vent is off-set to one end.  Can these vents only go in only one way or should I pay attention to which way the narrow end goes, up or down?

LOL, don't confuse me with those who actually do know what the heck they are doing!  I'm not in their league.  But if you have one of these, it helps:

 https://www.cbperformance.com/product-p/0101.htm

Maybe you can beg Pat Downs for an electronic copy since the hard copy seems to be out of stock.  In fact, maybe you could suggest CB offer all future reprints in an electronic format rather than restocking a publishing load of paper copy inventory.

One way or another, if you have Dells you need the CB tech book.  

I have both the Dellorto AND weber Thomlinson books.  For the most part, they get you in the ballpark and a line drive up the middle will drive in a run if you take it slowly and think about what your engine is telling you.   

Still, tuning carburetors is fast becoming a lost art in this world of commonplace electronic fuel injection.  Sometimes I feel like Doctor Zook - the dark-robed Druid from "Hagar the Horrible".

Doctor Zook

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Last edited by Gordon Nichols

Does anyone have a source for the fiber washers used on the Dellorto fuel supply banjo connections?  They are two different sizes on each connection and are showing as "no longer available" on the CB perf. website.  I assume we need to use fiber rather than rubber because the gasoline will attack the rubber.

I have a couple of carb rebuild kits on order and hope they show up in there, but would like to have a few extra sets in stock here, especially because they are often single use items that destroy themselves when you remove the fitting after they've been on there for a while.

Thanks,  Gordon

Thanks, PHB!   Got a source from Stan, too.  

Carbs are converted back to stock.  It was remarkably easy and took about 45 minutes per carb, including resetting float heights with a new gasket.  

Now, because I never looked for new washers before tearing them apart, they’re all dressed up with no place to go. 😖  Been looking locally but nothing so far.  When I order some I’ll get a bunch, for sure.   Thanks!

Re-reading that last post, it was kind of vague as to what I'm missing.

In order to set the float levels I had to pull the carb top covers and disconnect the fuel line banjo fittings, which destroyed the fiber sealing washers.  Practically no-one is using fiber washers on fuel lines anymore, but WE do.....   

I have a couple of carb rebuild gasket sets coming from CB (Thank you, Marieanne!) and I know they are in that kit, but they don't sell them separately and I would like to have some spares on hand for the future.  

What I CAN find is Chemical-Resistant Teflon PTFE washers just the size I need that should fit.

Does anyone on here have any experience using PTFE washers to seal fuel banjo fittings?  They certainly should be able to handle 15+ pounds of fuel pressure - people use them on EFI at much higher pressures.

I can't imagine that the fiber washers perform any differently than the Teflon replacements, but any feedback from you guys?

Last edited by Gordon Nichols

So I replaced the venturiis, got some seals for the fuel banjo fittings and took it out yesterday.  First thing I found was a partially clogged idle jet (I love how it "snaps" whenever an idle jet is suspect - makes my head turn to look at it and then I think, "I know what that is!")  

Blew out the jet and then a few other things surfaced (like it doesn't really like to idle when it used to idle steady as a rock) so, disgusted that my "quick fix" didn't work out and having received two carb rebuild kits from CB, I'm about to pull the carbs out, completely rebuild them to stock and start all over again.  I took a chance that I could just replace the venturiis and sneak it through, but no....Not gonna happen this time.

Hey, didn't someone else on here just go through this, too?  Ted?  Todd?  Beuller?

Someone with a 2,110 did a rebuild and then re-jetted to dial them in.  Don't remember if it was Dells or Webers, but I do remember someone.

Anyway, back to the shop.

Just finished rebuilding my Dellorto 40’s, yet again, to see if I can get over the mild transition stumble that I have had since day one.   I started out with the conversion kit to horizontal discharge tubes and I have to tell you, when that engine was pulling on the Main jets it is amazingly strong – the torque between 3,500 and 4,500 rpm (and higher) never lets up, but even up there it still had a slight hesitation when transitioning from any throttle setting (clue 1).  I overcame most of that with ever-increasing jet sizes and made it sort-of smoother, but not perfect.  Remember these are going on a 2,110 with MOFOCO 044 big valve heads and an aggressive port job, an Engle 120 cam, Berg 1-1/2" extractor and MagnaSpark II ignition.

Since there is nothing better than starting over when you're getting no-where, I went back to the stock, vertical discharge tubes and just returned my beloved Dells to the factory settings.  

Here's my collection of jets, the installed sizes in red, and the rest of the stock settings shown for reference: 

 Venturii size = 34

 Idle jet = 60   62    65    70

 Main jet = 130    135    140    162.5

 Air Correction =  160    180

 Accelerator pump jet  =  35    45   50    60    70

 Pump Squirt per stroke = .3ml/cc (I ran slightly heavy because it's a 2,110 engine) 

 Fuel Needle Inlet = 1.50

When I bought these Dells, back in the mid-1990’s, they were really different from anything I had worked on in the past, like Stromberg, Holley, Rochester, etc – all American production carburetors and all pretty simple – so I also bought the Tomlinson Dellorto Tech Book and referenced that to do the initial conversion to horizontal discharge tubes AND set things like the float height and drop (both of which were wrong out of the box).  I had a passing idea of the importance of float height as the basis for lean/rich idle circuit performance, but somewhere along the line I seem to have forgotten all that because American carbs are pretty simple to set and I hadn't touched an auto carburetor for 25 years when I got the Dells.

Anyway, Tomlinson seems to infer that you check float height by turning the carb top cover over and measuring the distance between the cover gasket and the float and set it to .1969” - .2364”. I chose something in the middle (.2185) which corresponds to a 7/32” drill which I used as my gauge.

IMG_0244

For float drop, you flip the cover over to “normal” and measure the float drop to the same gasket surface.  Range is .4728” - .5122” so the closest I had in my drill collection was a .5000” so that’s what it is.  That's the way I've been setting things up for 20 years and about the only thing that I've never changed. (clue 2)

Just for the hell of it, I googled “setting float height on a Dellorto DRLA 40” and got a few hits over on the Shop Talk Forums and the consensus there was to measure float height without the cover gasket in place (clue 3).  That would give us a final float height about 1 - 2mm higher than setting it with the gasket in place and THAT should push the fuel level slightly higher up in the emulsion tubes and THAT should make things slightly richer as it moves past the transition ports. 

Ancient experience, from 45 years ago, reminds me that this was the way to overcome transition stumble on Stromberg 97s (remember I said they were pretty simple?) so it should work here, too (I hope).  Don't know why this never occurred to me sooner.  duh.

So, I have now finished going back to stock (using the Shop Talk float level setting) and have everything back in the car and now……..  I’m afraid to go out there and start it up, just to find that it might be the same as before and I’ve gained nothing.

Maybe I can kill time and get over the anxiety by cleaning the shop.  Yeah, that sounds like a good thing to do……  That, and a cuppa tea.  Maybe a walk around the neighborhood.   Sounds good to me...

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Last edited by Gordon Nichols

So, I have now finished going back to stock (using the Shop Talk float level setting) and have everything back in the car and now……..  I’m afraid to go out there and start it up, just to find that it might be the same as before and I’ve gained nothing.

Maybe I can kill time and get over the anxiety by cleaning the shop.  Yeah, that sounds like a good thing to do……  That, and a cuppa tea.  Maybe a walk around the neighborhood.   Sounds good to me...

Be a big boy and rip the Band-Aid off Gordon. They will either work or they won't.

I know, I know.......   But this has been a curse of mine for 20 years now.  

I would think that the worst that can happen is that it improves but isn’t cured and then I’ll try raising the float level a tad more (next smaller drill size as a gauge) and see what that does.  It’s pretty easy to pop off the cover and reset the float but we’ll see what I get with the “factory” settings first.   Almost makes me long for fuel injection...

Gordon Nichols posted:

I know, I know.......   But this has been a curse of mine for 20 years now.  

I would think that the worst that can happen is that it improves but isn’t cured and then I’ll try raising the float level a tad more (next smaller drill size as a gauge) and see what that does.  It’s pretty easy to pop off the cover and reset the float but we’ll see what I get with the “factory” settings first.   Almost makes me long for fuel injection...

Gordon, you show what size jets you have now installed but how do they compare with the size of jets you removed ? 

Dave, with the old horizontal discharge tubes, I was running:

162 mains

160 Air Correction (per Pat Downs to help with the Horizontal discharge tubes)

65 Idle

70 Accelerator Jets

and the fuel level in the bowl was slightly lower.

OK, so my optimism was not rewarded.  I took it out around the neighborhood with everything back at stock settings and it runs terrible.

Popping through the throat on #4 and hard to get an even idle.  MASSIVE bog off-idle, like you have to pump it once, first, to get it to accelerate off idle.  All 4 accelerator jets are streaming, so tried backing off on the adjustment 1 turn - no change.  Tried to do a quick sync but when I turn the air bypass screws out to balance one side, the idle gets rougher.

I’ve had it.  I think I’ll just pull them and send them to someone who knows what the hell he’s doing and get this over with.  20 years of this is enough.

Gordon Nichols posted:

 

I’ve had it.  I think I’ll just pull them and send them to someone who knows what the hell he’s doing and get this over with.  20 years of this is enough.

If that's true, send 'em to Blackline Racing (801) 747-3342. Dave will hook you up. He's helped me when I've had something weird like a throttle shafts that were loose in the carb bodies, or return springs that weren't allowing the throttle plates to open fully. He does this all day, every day, and has for more than 15 years. It's not cheap, but you'll get everything you pay for.

If you're not ready to spend a bit of money (and I know about that Yankee thrift), remember how Bobby's (months and months long) odyssey was finally resolved-- with the discovery of a blown intake manifold gasket at the head. If your engine has ever backfired, it's a strong possibility. I'd take them off and figure on re-gasketing regardless.

Also: I know you rebuilt the carbs, but did you soak the bodies? I've pulled chunks of float out of one transition port or another that were worm-like, and at least 1/16" long. they didn't want to come out with normal cleaning. Blackline and Danny Pipereto completely disassemble the carbs and put the bodies and bits in an ultrasonic cleaner filled with a Simple Green or Pinesol solution, and leave them there at east overnight. Out at Blackline, they then soda blast them, and do it again. Once the bodies have gone through all of that, they blow carb cleaner down every single port before reassembly.

I'd do that at a minimum (blow carb cleaner through the straw down every transition port, with the jets and adjustment needle out)

Stan, I think that after 20 years of frustration and putting up with it, it would be money well spent to get this behind me.  

This last time, because I removed the carb from the manifold, I replaced the top manifold gasket.  The bottom is flange sealer, no gasket, but I removed the manifold (no indication of a leak, even between ports) and cleaned both it and the head flange with sealer solvent and 800 grit sandpaper - pretty much do that every time I have ever worked on them....  Gaskets are cheap - labor, too, when you're retired.

Both of these carbs look really clean both inside and out, but they are 20 years old, after all.....   I did not soak the bodies (while I agree that it certainly wouldn't hurt, if I had thought of it), but I blew out every passage after dis-assembly, first with Gumout aerosol (I use it pretty liberally) and then with compressed air.  Pulled the transition port inspection plugs, blew the ports out with both and then inspected them with a 10X eyelope - nothing in there.

Kind of thought about this all night and have decided that, even though I once was comfortable rebuilding (American) carbs (and have done a lot of GM 350 carbs), on the Dells I had nothing to tell me what parts, especially o-rings, to use where, other than comparing what came out to what I had in the kit.  What if I used the wrong rings somewhere, like on the bypass screws or mixture screws, because using the correct, larger one made it difficult to get the screw back in?  I would never know, but someone who does this daily certainly would and it would be done right.  It would be really helpful to line up the little o-rings by size, number them from #1 to #whatever and then in the rebuild instructions say "replace the airbleed screws using #2 o-ring" to eliminate confusion and error.

Anyway, that's it.  Time to get out the checkbook and end this drama.  I just want to drive it, Yankee frugality be damned.  I've already put enough time and money into this over the years to buy another pair of Dells.  I just want these to work right and I realize that I can't get them there.  I want to get them back from somewhere, put them on and have them work on my engine.  That's not too much to ask, is it?

Stan Galat posted:

Yeah, but they'll still be "as new". If the problem persists, he'll be able to look elsewhere.

I've been coming to the SOC for 19 years, and Gordon was here when I arrived. This is the first time in my recollection he's ever given up, so I'm wishing him the best.

Same here. Just don't want anyone getting their hopes up too early. Hope for the best prepare for the worst. And if there is still a problem he'll have one less place to look.

Well, they worked sorta-worked well for years, just “not right” and I lived with it.  They were better before I rebuilt them this time and screwed them up. So, I figure that if they come back rebuilt properly and pre-tuned to my engine specs (which I send out with them) then the only wild card left is manifold gaskets, which will give me popping ( not snapping as with a clogged jet ) or idle speed hunting.  Both easy to find and fix.

After talking with Dave at Blackline, I have confidence that he understands what’s going on and knows how to fix it, based on a LOT of experience.  

Experience that I do not have - Simple as that.

 

Gordon, I think I get why you're letting Kodak do the rest.

After 20 years of putting up with this, you're certainly the best judge of when enough's enough.

But frankly, I wasn't expecting them to run right immediately after resetting everything to 'factory' specs. If I've learned anything about these carbs, it's that nothing is predictable. You've got to start with whatever you've got, listen, and then gradually nurse it to where you want it. And at least some of the numbers end up being not what you were expecting them to be.

Mine likes 57.5 idles. Moving down one notch to 55's makes all hell break loose. The bibles and the gurus say that shouldn't be. But on this motor, it is.

I had everything dialed in perfectly for like, a year. One day, someone following me said I was running 'a little rich'. I changed the mains down from 140's to 135's and, again, all hell. I had to change all the mixture settings and L to R balance to bring things back in line. But it still would only run right when warm OR cold - not both. I gave up and went back to 140's. But it still ran like crap until I was gradually able to dial it in again. A month later, I was finally back to where I'd started.

I'd think with everything new, it would take at least a few weeks of tweaking to get balanced again.

Another thought is that, after 20 years, wouldn't the main shafts (what the butterflies are attached to) be loose in their bushings (or bearings, or whatever they ride in)? I thought that all carbs had to be rebuilt in time to fix that.

In any case, what you're doing should get any such issues resolved.

 

I can deal with a little bit of dialing in.  We dialed in Snowmobile carbs, some of them three-barrel, some of them multiple singles, for years so that part isn't new and I know how to take it slow and one step at a time.  I could partially mask a fault on the Dells by playing with jetting and got it to run OK, but there has always been something fundamentally out of whack that I haven't understood enough to cure it, nor do I have a selection of parts (other than a bunch of jets) to change basic airflow characteristics.

I just believe that these were never really "tuned" for my particular engine requirements from day one, like matching venturii size, air correctors, jet size, all that jazz, to what the intakes, cam performance and exhaust expect to see.  All I did was buy a pair back in the mid-1990's, supposedly set up for a 2,110 right out of the box, when in retrospect I just got a generic pair of 40mm Dells (that I now believe might have performed better on an engine with a milder cam).

What really made me a believer in Dave at Blackline was that he asked for the head and cam specs and compression ratio, along with basic carb specs right at the beginning of the conversation and made a few comments as we went along that were dead on with what my air/fuel gauge has been telling me (and I thought it was just a cheap gauge giving me false readings).  Without ever seeing the gauge in action, Dave told me what the engine should be doing and that's what the gauge said, too!

Anyway, I'm boxing them up, and, listening to Horace Greeley, I'm "Sending them West, young man!" to the land of Shake Tauffler to see if they can become born again for their second act.

While you're waiting, weld in an O2 bung. Unless you already have one, I think I remember you having a narrowband a while ago. You are welcome to borrow my wideband gauge and sensor and that way you'll really KNOW it's set right. They are definitely less expensive now than they've ever been. And god forbid it still acts up when you get the carbs back, you'll at least be able to follow what's going on and fix it.

At $125 this is pretty cheap, and is the one I own. Mine is wired up to a cigarette lighter. I have a plug in the exhaust bung as once you are dialed in, it's not needed. I got rid of my self-caused rich bog due to the velocity stack air interfering with my Jet Doctor air. The AFR gauge really made it obvious what was happening.

http://www.wide-band.com/product-p/wb_d2n.htm

Good luck, Gordon

Yeah some things get fixed much faster by using someone else with experience rather than learn it yourself  but I like Danny’s solution that bung allows you to tune your carbs with some intelligence rather than faith

i have one on my subie and my tuner wants me to have an ecutec tune done by him to alleviate some nuances that sometimes these custom cars bring to the écu which makes it try to adjust near the high range at times not giving you any leeway after this for self learning  

Last edited by IaM-Ray

I've had a heated O² sensor since 2004 or so.  

While it helped me make things a bit better (and was great at pointing out a clogged jet and/or manifold leak), I was not experienced enough to fully understand what it was telling me or how to change things for the better.  The gauge apparently was pretty accurate, but my understanding and experience was lacking.  My brother would have known how to fix this, but by the time I got serious about fixing it he had passed.  

Time for a new chapter. One that starts out in a much better state.

Lots of times, starting the learning process from a point where nothing is badly broken is really helpful. The thing that makes carburetors so difficult is the multiplicity of factors involved: venturi size, velocity stack height, float height, main jet size, air corrector size, emulsion tube type, idle jet size, accelerator pump jet size and adjustment, etc. Every change has some secondary outcome.

Also factor in the number of potential problems, not just “tuning issues”, which are often not bad enough to be obvious, and present as tuning issues. Carburetors go out of sync, intake manifold gaskets develop leaks, idle jets partially plug, ethanol in fuel attracts moisture and collects in the fuel bowls and creates a jelly, crud gets stuck in transition ports, etc. Ignition and mechanical problems also seem like carburetor problems, probably because there are so many things to go wrong there, it just HAS to be there, right?

Getting the carbs back in tip-top to start with provides a good starting point. Good on you, Gordon for biting the bullet. 

Gordon Nichols posted:

Yeah, but if I keep this up I’m gonna start looking for Five Cent Racing sponsors to help pay for stuff.....   🤨

I knew that “Yankee Thrift” was eventually going to pop its head up.

A long time ago a guy told me, “Son, if you wanna’ run with the big dogs you’re going to hafta’ learn to pee in the tall weeds”.

A less obtuse version of that would be, “If you want to play, you have to pay”, or the ever-ready, “Buy once, cry once”.

Feel free to choose the idiom that suits your situation the best. 

 

Life was much less complicated when I was living on an expense account.  

Hey, BTW - I just finished reading “The Art of Racing in the Rain” by Garth Stein and now I wanna see the movie.

Not at all what I expected, but it was a terrific read (I literally finished it at 1:45 AM last night) and I expect the movie to be pretty good, at least.  Several nice tutorials on track driving and some common sense views on dealing with life (and death).  

Last edited by Gordon Nichols
Stan Galat posted:
Gordon Nichols posted:

Yeah, but if I keep this up I’m gonna start looking for Five Cent Racing sponsors to help pay for stuff.....   🤨

I knew that “Yankee Thrift” was eventually going to pop its head up.

A long time ago a guy told me, “Son, if you wanna’ run with the big dogs you’re going to hafta’ learn to pee in the tall weeds”.

A less obtuse version of that would be, “If you want to play, you have to pay”, or the ever-ready, “Buy once, cry once”.

Feel free to choose the idiom that suits your situation the best. 

 

I like the one that says " figure a way to do it on OPM ".  It's worked nicely for me from time to time. 

mppickett posted:

I'm guessing that in this case OPM means "other people's money" rather than "Organic Pest Management."  :-)

Exactly Mike but I do it in a useful and legal way though. Spent a lot of time sailing in the Carib, Bahamas and Florida years ago as a yacht charter agent. Been in the ring with Mike Tyson while managing ( not so well ) a Canadian Heavyweight boxer Conroy Nelson. Latham Coliseum , NY Nov 22, 1985. etc. 

Last edited by David Stroud IM Roadster D
Gordon Nichols posted:

I've had a heated O² sensor since 2004 or so.  

While it helped me make things a bit better (and was great at pointing out a clogged jet and/or manifold leak), I was not experienced enough to fully understand what it was telling me or how to change things for the better.  The gauge apparently was pretty accurate, but my understanding and experience was lacking.  My brother would have known how to fix this, but by the time I got serious about fixing it he had passed.  

Yes, I thought so. I think they are all heated. But is it wideband? As I recall, it was a narrowband unit which is pretty useless on a non-EFI car. The best way to use one is to have someone else drive the car as you watch it or vice-versa(do it with Chris, he's who I'd choose). Or datalog it, they do have an output channel.

When we last left our intrepid DIY auto hobbiest, he had thrown in the towel on his twin 40mm Dellorto Carburetors and declared defeat - those pesky Dells had proven to be his match and refused to run as well as everyone knows they should (Re-read from the top of this thread to get the whole, sad history).  They were pulled, drained, aired out overnight then tagged and bagged and sent via UPS to Dave Hogland at Blackline Racing out in Murray, Utah, not all that far from the Bonneville Salt Flats (See?  Blackline Racing - Out on the Flats!  Building engines that WIN!)

Once I described what they had in them, what the engine is and how they had been responding, Dave described, to a "T", how they had been acting (even corresponding to my air/fuel mixture gauge response) and told me of a "most likely" fix:

  1. Drop the primary venturiis from 34mm to 32mm
  2. Drop the Main jets from 162.5 to 130
  3. Drop the idle jets from 65 to 45
  4. Drop the accelerator pump jets from 60 to 35

Dave cleaned them and rebuilt them with the above jetting and tuned them on a 1915cc engine with similar characteristics to my 2,110 (cam, compression, etc).  He also noted on my poop sheet that I run Bosch Platinum 8-range plugs (W8AP) and recommended that I go to an NGK non-platinum BR6HS spark plug gapped at .032 (for my Magna Spark II hotter coil) because he hasn't had a lot of good luck with Platinum-tipped plugs in VW engines.  I used Platinum plugs on a LOT of snowmoblie racing engines (both carbureted and EFI) with great luck but, hey!  PLugs are cheap, right? so those got swapped out, too.

Remember, my biggest complaints were a big hesitation/bog right off-idle and a transition hesitation at almost any speed above idle.

I am THRILLED to tell yah that both of those are totally gone and these things are running so smoothly they feel exactly like the EFI in my Nissan Rogue.  

I pulled them from the shipping box, did absolutely nothing to them, installed them on my intake manifolds, connected the linkage and started it right up.  I saw none of the coughing or puking that I had become used to at cold start-up and it settled down to a nice idle after about 15 seconds (?!?!?!?).  A quick road test around the neighborhood showed zero hesitation at any rpm up through third gear and when you stomp on it at any RPM (below 3K - it's a quiet neighborhood) it just simply takes off - no hesitation, no lag, no bogging, it just goes.

Stan was right about me, I'm a cheap kinda guy living on retirement income and having this done was not inexpensive, but considering that I spent 20 friggin YEARS trying to figure them out and failing (and probably spending almost as much over those years in wrong parts and labor and just messing around), I think this was money VERY well spent.  It certainly pays to pay someone who really knows what the hell they're doing and the guys at Blackline certainly do.  They have a 3 week backlog on Carb stuff and a 6 Month backlog on engines, but these guys are really, really good.

If I had started with carbs that had been running and were appropriately set up for my engine I would have started out on a much different foot, but that's whiskey under the bridge.  I've finally gotten to where I want to be, this engine is running like a watch and it is really fun to drive.

Snoopy Dance

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Last edited by Gordon Nichols

I know what you mean Gordon, with the often low quality results of purchased work when it comes to our cars and with the dwindling mass of good techs you feel, especially when your retired that you need to get good value for your money. ok, you can say, cheap, frugal etc etc.  And while they may describe the behaviour sometimes you end up chasing a problem and spending more money digging a hole.  This is the story with my Fuch front wheels we thought the tires were still worth keeping and after spending more than nearly twice the money for new tires on chasing a balance issue I finally just changed the tires and voila it was cured... DUH... yeah big DUH.  

 

GREAT NEWS on your fix. 

Last edited by IaM-Ray

 

Good news, Gordon.

It's comforting to know that you can still get what you pay for if you do your homework first.

I wonder if half of our tuning woes don't come from not wanting to be the guy with the little girly-man jets or venturis. After all, everyone knows that bigger jets make more power, right?

And why have Weber 40's when real men run honkin' 44's?

I'm betting your gas mileage will be better, too.

 

Thanks, Ed.  

Admittedly, the really large jets I was running was to compensate for the change I made to the horizontal discharge tubes before I had ever run the carbs on my engine.  I drank the "Hot VW's" Koolaide about getting every possible horsepower gain from the engine way before I even had an engine, so when the article said "you can get 10 - 12 more hp with this kit", I went for it, little knowing that, yes, it gives you a bit more boost, but all of it on the top end while making the rest of your driving (at least in my case) less than a great experience.  Getting to something more drive-able from that point went slightly beyond my understanding of what's going on in a carburetor and how it all inter-relates, so I was lost.  Give me a basically working carb that needs to be jet-tuned and I'm OK, but when the basic working structure is flawed to begin with I simply didn't know how to proceed (without spending a bundle on parts that didn't fix the basic problem).  In the past, every time I did carb tuning it was on something that had been running, but needed tuning after something else on the engine changed - usually something pretty minor.  This went beyond my experience.

What Blackline did for me was two things:  (1.) they made sure I didn't screw anything up when returning the carbs to stock from the horizontal tube debacle (and finished the reversal by removing a couple of lead port plugs I installed as part of the kit) and (2.) set them both up based on the specs of my particular engine; displacement, valve size, intakes, exhaust an, most importantly, what the cam is doing.  That, in itself for someone who never had stock, working carbs in the first place, is priceless, so for the few hundred it cost me to get there it was money well spent.

The rest of this week is supposed to be gorgeous weather and I intend to be out there, in my car, enjoying it!

Oh, and if any of you guys are in the Salt Lake City/Murray, Utah area, please let me know of a really decent restaurant that I can get a gift card from to send to Dave at Blackline.  He deserves it.

I'm glad you solved your problem, Gordon. Really glad. Blackline does good work.

Don't forget to do a high speed synch on those puppies!

But, had you purchased the WIDEBAND O2 sensor, you could have figured it out. 

I figured out a problem with short velocity stacks/CB Jet doctors/falling on it's face at transition with the wideband. The fix? Taller stacks to disconnect the idle air intake from the rush of air going down the throat. Really, fixed like an a switch, from awful to perfect. Because I could see real-time how lean/rich it was in transition, under load.

BTW, Lenny put the horizontal discharge tubes in his Dells this spring, and bought some jets and jet drills and a wideband. Dialed it right in.

Yeah, Pat Downs told me that the “new” horizontal discharge tube kit (as opposed to mine from 1998) is more suited to stock venturiis and seems to work better.  For me, I’ve got this thing running like the proverbial Swiss Watch and am not gonna change anything.

Well, actually, to that point, I thought it was lacking a bit more idle circuit “kick” when you stomp on it and my elCheapo whatever-band gauge was showing me a very slight leaning swing (although way less than what it used to have) so I cranked up the accelerator pump strokes a tad and that gave me perfection - PERFECTION!!!  Dave told me I might have to do that, too.  I suppose the difference was due to the carbs both being originally tuned on a different engine.  That’s my story and I’m stickin to it.  

Now, I can take off gently with zero hesitation whatever, then can accelerate smoothly in any gear with no lag up to where the Mains cut in and the heads really start to flow and then.......  I LOVE IT!!!!!  💕  It is a gentler car to drive but can still take off like a rocket if you really get on it.  Best of both worlds.

Pearl is absolutely fun to drive again!!

Last edited by Gordon Nichols

I've been in Europe for a bit (still am-- Strasbourg currently) and missed this, @Gordon Nichols. I'm really, really happy it worked out.

A bit of history:

Back in the early 2000s, when Jake Raby was posting on all of the VW forums, he talked about how Art Thraen's shop (ACE) in Salt Lake did all of his carb work. I paid attention, and called Art when a set of AJ Sims Kadrons was kicking my butt back in 2006. At the time, Art was running ACE as well as a thriving HVAC service company at the same time, so he and I had something in common and hit it off. Art politely let me know that Kads weren't really what I wanted, and steered me into a set of "Dave rebuilt" Dellortos from his shop. They were expensive, but I was desperate. When I got them, they were everything Art said they would be. It was the beginning of a great relationship. Art's shop built 3 motors for me, and I stayed in Art's house twice (once in 2012 and once in 2015).

Blackline Racing is owned by a young man named Justin McCallister, who was Art Thraen's chief mechanic at ACE before purchasing Art's business 5 or so year ago. Dave had been Art's carb guy for many years before the sale of the business, and carried on in that capacity after ACE became Blackline Racing. The sale was a win/win for everybody involved. Art is now happily running his HVAC business, Justin is doing what he loves, and Dave is happy as a clam at the carb bench, doing for other people exactly what he did for Gordon.

When I think back on meeting Art-- he probably kept me in the hobby. I was pretty much "over" the whole thing when our paths crossed. Art got me pointed in the right direction, and got me set up with what I needed. From there, I learned a ton about what was going on.

The service isn't cheap, but when you consider how many guys have just thrown in the towel on carbs (never really getting them right), and how many have gotten out of the game altogether-- I think it's worth every penny they get. At this point, I know my way around a set of Dellortos well enough to do pretty much anything I need to do-- but I've still had a couple of sets rebuilt by Dave in the last 5 years, for the same reason I hire out some of the things I can do myself at work-- this is what Blackline does every single day, and they will come back perfect. Sometimes, it just pays to let somebody else do what they do, so I can do what I do, and everybody can earn a living.

I had a bad backfire last year and melted an entire aux. jet on my 1/2 carb. I got all the parts together from several different places in Europe, took the carbs off and sent them to Dave. During the rebuild, he found some slop in the throttle shafts and that the return springs were binding to some extent. I got the new shafts and springs from Italy, and Dave put them together. All of this happened during the heat of summer, when there was no way I could have gotten to it. It was not inexpensive, for sure, but totally worth it.

I feel good about giving money to the good guys in this hobby. Blackline Racing are some of the good guys.

Last edited by Stan Galat

Truly intelligent people realize their limitations. They accept that they don't know everything and surround themselves with or use the services of people who are truly experts in their fields. In business this is a sign of a good boss and in a hobby such as ours can be the difference between a successful experience and giving up and walking away in disgust.

Amen, Brother Al.

But even when it isn't a matter of limitation-- it's often a matter of time. At this point in my life-- time is worth more than money. I get paid more for my time then I did when I learned how to do a lot of stuff, but time is something that cannot ever be earned back. I'm getting kinda' jealous with it as I can see it slipping away.

Sometimes, it just pays to let somebody else do what they do, so I can do what I do, and everybody can earn a living.

Last edited by Stan Galat

Wow, Stan......I have actually never been to Strasbourg, either in Germany or France!!

No idea what that means, other than it provides an opening to this post.

I suspected what mine needed were smaller venturiis (turns out, they did, but I was far from sure), but by the time I were to buy those and do yet another rebuild, I would have been close to Dave's invoice amount.   And then, would I have bought the correct size?  And how would I know that before buying them, other than guessing?  and was there anything else that needed to be set right?)   I knew that he would know what to do, fix them right and then test them on a known engine...   Priceless!

We've both mentioned that this type of work (or anything done by a specialist in any field these days) isn't cheap, and in mentioning that we may be scaring people away from some excellent service.  In the time it took me to play with them and play with them and get them sort-of running well enough to be street-able, America has gone through three Presidents and is on our fourth.  That's quite a while and all that while they were always a little off.

Dave quoted me $265 for rebuilding TWO like carbs.  That's under $150 EACH.  That includes the rebuild kits (usually $40 at CB).  Add to that the price of four new primary venturiis (For somewhere in the ballpark of $15 each) and testing then them on an engine and the whole shebang came in around $375 including return shipping (and it cost me almost $50 to UPS them out there, so it must have been close to that to get them shipped back).

To pay that amount and get something back that truly ran extremely well right out of the shipping bubble-wrap, while amazing, is kind-of what you expect from a specialist, right?

I would highly recommend Dave Hogland at Blackline Racing to anyone wanting to get their carbs rebuilt and want them done right without screwing around.  I am so glad that I followed Stan's advice and did this right.  It's made all the difference in my driving experience.

Enjoy Strasbourg, Stan......   Where-ever it is!   

That's not outrageous, Gordon, to know that when you get them back they are set up for your engine combo and will operate as designed. The problem (with the VW hobby as a whole and somewhat infecting our side of things)- too many people are cheap a**ed, expect to pay prices more reminiscent of 20 and 30 (and 40!) years ago and bitch when they have to pay for anything built to anywhere near oem quality standard. There's a reason for the dirth of sh*t parts out there- put the cheaper crap beside the properly designed and built part and the crap will sell (almost) every time.

Stop this rant and get off my soapbox now I will..

And I agree with you Stan, as we get older...

ALB posted:

That's not outrageous, Gordon, to know that when you get them back they are set up for your engine combo and will operate as designed. The problem (with the VW hobby as a whole and somewhat infecting our side of things)- too many people are cheap a**ed, expect to pay prices more reminiscent of 20 and 30 (and 40!) years ago and bitch when they have to pay for anything built to anywhere near oem quality standard. There's a reason for the dirth of sh*t parts out there- put the cheaper crap beside the properly designed and built part and the crap will sell (almost) every time.

Stop this rant and get off my soapbox now I will..

And I agree with you Stan, as we get older...

When I got my car and entered into this hobby I told myself I wouldn't cheap out on anything. And so far I've been true to my word. And so far nothing I've fixed has had to be redone. If you have enough disposal income to play with plastic cars then you probably have enough money to buy decent parts. If you don't, it's probably because you're just cheap.

Gordon Nichols posted:

... I have actually never been to Strasbourg, either in Germany or France!!

No idea what that means, other than it provides an opening to this post...

... Enjoy Strasbourg, Stan......   Where-ever it is!   

It means that 9:00 AM where I am is 3:00 AM on the east coast, and somehow I missed your post of success until yesterday. Posts from home generally show up while I’m sleeping.

It’s Strasbourg, France, and yes we did enjoy it— very much! 

D1F71CEA-2783-40E8-ABD8-172D456DC92A

On to Lyon!

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Gordon  --

I've been following this thread, and where your carbs have led you to this point. 

Until just recently, I have felt pretty comfy and confident about technical stuff with my carbs, and 'two-barrel' Dells / Webers in general.  Now, I have to say, even I am at a loss, unable to nail down a problem I'm having.  It's one of those things where I know exactly where the problem is and I've eliminated everything I know that might be causing it.

So I'm sitting here in self-doubt thinking I must have "missed it" or did it wrong first time through.  And, only a full re-do of the elimination process  (probably including my doing a repeat complete carb knock-down and rebuild) is next in my future.

But,  as I've seen mentioned by others elsewhere in this thread, I'm also starting to feel like I'm getting a little old for this (the hands get a little shaky after a while, the patience wears a little thin, the back gets a little tired, etc.).  So I called my wife in to read your post yesterday about Blackline.  She then asked me:  Why am I still messing around?  Send in the cabs.

Obviously she doesn't 'get it'.  She doesn't understand the machismo of Man vs. Mechanism.  In her mind she probably also follows some twisted logic that if my thumb hurts I should stop hitting it with the hammer.  

On the other hand, she might be right; again.

Oh my God........

I'm gonna put that in a nice font, somewhat larger, and hang it on the wall of my shop.

Maybe even send a framed copy to Dave at Blackline, if that's OK, Mitch.

Mark:  Just do it.   Dave at Blackline sees these things every day and knows what is good and will work properly and what won't from vast experience.  He'll see something a little out of whack that I probably would miss, and I've been successfully rebuilding (but not necessarily modifying) carbs for over 50 years - lots and lots of them.

But I've been pretty busy with some volunteer work and when it looked as if I could spend a bunch of money on my own to maybe make things better (or probably not, you know?) or spend just a little bit more and have them done right by someone who really knows what he's doing and make them just like new again, well that convinced me.

Just do it.

Thanks again, Mitch!

You know, Mitch deserves the credit for this wonderful poem so I have deleted the original post with the PDF files and have attached new versions here - Crediting Mitch.

Seems only right.

Again;   They were created as an "A" size (8.5" X 11"), exported as a PDF that should scale up well to a "B" (11" X 17") or "C" size (17" X 22") but may get a little fuzzy on the background image at that size (the Weber image is around 2480 pixels square, the Clown a bit less).  

Any "Staples" store can accept a PDF and zoom it up to a B or C for you and print it in color (even laminate it for you).

Thanks, Mitch.

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Well, I guess I won't be posting the poem on my garage wall after all.

In my funk of dejected surrender I decided to pull the carbs to get ready for send-in.  But before I could even pull open the drawer on the tool chest I couldn't help myself and decided to take one more swing at it.  I just couldn't come to grips with defeat.  The carbs are simple mechanisms, I've been through them several times, I think I'm experienced enough to pretty-much know what I'm doing and why; how could it be that they beat me?

The problem was simple enough to identify: #1 ran sometimes off, sometimes on, sometimes iffy; and only on the idle circuit.  I had already installed a new gasket/o-ring kit after carb spray cleanout.  Spark was not a problem.

Lesson learned:  Sending-in the carbs won't help if you keep reusing the carb base gasket.

The dim light went off when I pulled the carb and noticed the base gasket was wet, on the #1 hole.  I didn't have another gasket (it doesn't come with the gasket/o-ring kit), which is why the base gasket kept getting reused.  But I did have some gasket material so I cut for myself a new one.

After a 55 mile test drive yesterday, I think I'm good-to-go.

Glad you were/are resourceful enough to cut your own.  

Well done!  

I usually use the one-piece bottom gasket but this last time I had a bunch of the smaller ones (single throat each) kicking around and used those, but my old friend, the dreaded “Dellorto Whistle”, came back but this time I’m treating the whistle as a badge of honor.

”Hear that?  It whistles when it’s really cookin!”

 

So, here is a question for someone:  What size fuel inlet/needle valve is right for me?

I have 48 tri-jets on CB mini wedge-ports, 2332.

Rebuild kits I bought some years ago came with 2.00 fuel inlet/needle valve.  That is smaller than what what was installed, so I stayed with the originals that were installed (which are somewhere larger than 2.00 but smaller than 3.00).  At some point I should replace the inlet/needle valve.  Is there any drawback in going all the way to 3.00?

Not sure the Weber fuel inlet/needle will fit my Dellortos, but I did follow the aircooled site to these: http://vwparts.aircooled.net/D...-needle-seat-250.htm  (which is probably what is installed).

The reason I asked about maybe going to 3.00 is because sometimes when driving "sporty" through pedal pumping up and down shifting, pretty much all at 4000-6000 rpm, it seems like I empty the float bowls (run out of gas) in about a mile, maybe two.  I know for sure I have good pump flow (Carter pump), clean filters, and good regulator.  I can fill a quart jar from the regulator output fast enough to fuel a locomotive.  So I was wondering if a larger carb fuel intake hole would be better.

Aircooled says 2.50 is big enough for "wilder engines over 200hp", so it sounds more than big enough for me, for sure.  Maybe I'll have to think elsewhere about my problem.  When it happens I just have to pull over and idle for a short period, or coast with the engine off/fuel pump on.  Then everything is ok again.

Thanks for the link, Gordon.

 

 

Have you tried running your floats up a bit to richen it a bit?

Then, if you’re seeing fuel starvation above 4K with 2.5-ish pilot valves, then, sure....... try a pair of 3.0s.  Then, if that doesn’t fix it, go to higher fuel volume delivery and see if that helps.  What the heck, pilot valves are (reasonably) cheap, right?

HOWEVER!  If you pull over and idle to “recover”, the bowls should re-fill to recovered level in less than 5 seconds.  Does that sound like what you’re seeing?

Other things might be the wrong spark plugs installed or a questionable ignition module or coil breaking down under stress.  

What, exactly, happens above 4K when you see this?  I’m trying to decide if it is fuel starvation or high rpm electrical breakdown.

RS-60 mark posted:

Not sure the Weber fuel inlet/needle will fit my Dellortos, but I did follow the aircooled site to these: http://vwparts.aircooled.net/D...-needle-seat-250.htm  (which is probably what is installed).

The reason I asked about maybe going to 3.00 is because sometimes when driving "sporty" through pedal pumping up and down shifting, pretty much all at 4000-6000 rpm, it seems like I empty the float bowls (run out of gas) in about a mile, maybe two.  I know for sure I have good pump flow (Carter pump), clean filters, and good regulator.  I can fill a quart jar from the regulator output fast enough to fuel a locomotive.  So I was wondering if a larger carb fuel intake hole would be better.

Aircooled says 2.50 is big enough for "wilder engines over 200hp", so it sounds more than big enough for me, for sure.  Maybe I'll have to think elsewhere about my problem.  When it happens I just have to pull over and idle for a short period, or coast with the engine off/fuel pump on.  Then everything is ok again.

Thanks for the link, Gordon.

 

Do you know what camshaft is in your engine- if not, how high does the engine go with power in 3rd gear? What does your car have for a fuel pump? Is the fuel line running through the tunnel still stock?

The reason I'm asking these questions- there's a guy on the Samba with a 2180 (FK8 cam, IDA's), goes to 6500 with power) and Berg 5 in a bug that when drag raced from a standing start drains the float bowls just about the time he shifts into 5th gear. If he hesitates for 1/2 second it's got gas again and away he goes (not that he does that much, as at that point he's doing well over 100mph!). He runs the stock fuel line and pump and they actually can't keep up under sustained full throttle operation, but IDA's hold so much gas that for most owners it's never a problem. A lot of IDA owners open up a blank chamber inside the carbs to make even more fuel available so they don't have to upgrade the fuel line or pump and it works, but it's a bit of a bandaid and not actually the solution to the problem.

Is it possible the pump/fuel lines can't deliver enough gas?

PS- I see you're running a Carter pump- are you sure it delivers more volume than a stock mechanical pump? How big are the fuel lines? Does the tank have the stock fuel fitting or something with a bigger diameter on the bottom?

Last edited by ALB

OK, I'll take Pat's 'no' on the 3.0 as a definitive don't do it.  Thanks Pat for putting that question to bed!

To answer a couple of questions quick:  The cam is W110, which (yeah I know) I outgrew a lot of modifications ago.  Still, it seems to pull to 6000 which is more sensory overload than I ever need and never exceed (on purpose).  If I ever split the case again, I'll change it, just because . . .

As mentioned, the fuel pump is a Carter.  The regulator is Malpasi, with verified adjustment to 2.5 static pressure.  The rubber fuel lines are all 3/8 ID.  3/8 OD stainless tubing makes the fuel line run from front to back and presents the most restrictive hole in the chain:  .30".  The stainless fuel tanks are custom, with basically a 3/8 ID hose in the tank attached to a 3/8 OD nipple out of the tank. 

Altogether, I am pretty sure I have plenty of fuel delivery to the carbs.  I've proven this to myself several times over the years by disconnecting the fuel line from the carb intake banjo and running the pump to fill a quart jar.  There is no way I could use gas as fast as I can fill a quart jar; if I could, I'd run out of gas between gas stations.

All of this is what led me to the question about the fuel inlet/needle valve size, since that is the most restrictive hole in the supply between fuel tank and float bowl.  And, until last week I didn't know they came in different sizes.

But after Pat's reply (and Gordon's questions), I'm starting to rethink everything.  I've always thought I was running out of gas.  But what if it was the opposite, what if I was flooding too much gas!?  Apparently that's possible, according to Pat.

So off to the garage I went, and rummaged for the baggie marked "used Dellorto parts".  In it I found both carb's fuel inlets that I replaced more than 15 years ago when I first rebuilt the carbs.  Out of curiosity I found that a 1.19mm drill bit was very loose in the inlet hole, and a 2.38mm wouldn't fit.  So there is a good chance the inlets I removed way back then are actually 2.00mm.  And since the inlets that are now installed have a hole bigger than 2.38mm and smaller than 2.79mm, I'm betting the inlets are like 2.50mm.  Not knowing any better, I guess I replaced the 2.00 inlets back then with 2.50.

Well, if 3.00 is an assured flood-a-rama, is 2.50 also too big?

So here is what happens behind the wheel:  First of all, I have to be 'trying' hard to make it happen, ae, thrashing it.  And since I know it might happen when thrashing it and for other common sense reasons I don't go thrashing often.  I never notice the problem in normal 2000-4000 rpm driving.

What happens when thrashing is it starts cutting out as it begins loosing cylinder(s) within a minute or so of hard throttle pumping up and down shifts basically all over 4000 rpm.  The remedy is to let it work itself out while idling along side the road or slow rpm driving.  This may take a few minutes, not a matter of seconds (to answer your question Gordon).  Eventually the engine smooths out and everything is OK again.

Can it be that instead of running out of gas in the float bowl as I've been suspecting, is in reality that I am flooding it with too much gas and temporarily fouling the plugs?  And, once they've had a chance to 'dry out' by puttering alongside the road, I'm good-to-go again?  

 

 

 

I do have some new 2.00 inlets/needles.  Thus, if I had good rationale to split the carbs and replace the inlets/needles, I could.  But I'd only want to do it once, with some assurance there is no downside to downsizing the fuel inlets.  They need to supply:  2332, CB ported MiniWedge heads, DRLA 48 Tri-jets; without running out of gas (going lean, and burning valves/pistons) reving between 4000-6000 RPM while pumping the accelerator jets during quick corner to corner upshifts and heel-toe downshifts.  So, am I OK to downsize fearlessly?

Distributor:  009 with Compufire module.  Yes the module is screwed tight and base grounded.  Is there enough temperature difference in the distributor between times of "normal driving" and a brief minute of pretend road racing to cause breakdown and recovery from one minute to the next?

 

Last edited by RS-60 mark

Compufire modules seem to be built better (and be less problematic/affected by heat) than Pertronix modules so I would think (for the moment) maybe Michael's idea that it could be the coil acting up when getting hot is worth looking into. While not exactly common, it's not unheard of for coils to fail like this, and I wonder if significantly hotter underhood temps could be contributing to the problem? A remote thermometer in the engine compartment would be 1 way of determining what's going on. 

Hope this helps. Al

Hi Al, all comments are helpful, especially from you and the guys in-the-know.  And I'm sorry for hijacking Gordon's thread.  As far as underhood temps, in my case they are unlikely to make radical swings up and down after a minute of hot rodding followed by side-of-the-road idling.  If anything, they are likely to be somewhat higher when stopped/idling than moving down the road (at any RPM).  I have a spyder (not 356).  Click on my avatar for a picture and you'll get the idea; everything under the body that's rear of the firewall is open to the ground.

I'm still of persuasion the problem is high RPM fuel delivery related (either too much or too little), not electrical. not temp.  

PS:  I do have Tri-Jets which are designed to add raw fuel enrichment at high RPM.  I question if they actually ever come on at the kind of RPM/vacuum my engine generates.  But if I was already borderline flooding and the Tri-Jets did come on at high RPM, compounded by accelerator pumping; that might be a factor.  Any merit  in that kind of thinking?

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