Hi everybody - I have what I suspect is a recurring 'boiling fuel' issue with my VS car.  I live southwest of Denver, CO at about 6500' elevation. I have a stock 1915cc, dual Kadron setup, with a stock mechanical fuel pump. The only modifications have been to 'seal' up the engine bay with additional tin beyond what VS Arizona did with the original build (this was done by local pro flat-four guys). I have been using the highest octane fuel conveniently and readily available, but in this part of the country (probably like almost everywhere, these days) oxygenated fuel is a staple. For what it's worth, I'm running Motul 20W-50, and the car has about 1100 miles on it.

My issue is this: I drive the car for 30 to 40 minutes or so and the car runs perfectly. Then, I stop for a coffee or a breakfast (anywhere from 15 to 45 minute break) with ambient temperatures now climbing into the low to mid 80's.  Climb back into the car, and although it starts right up and idles fine, it basically runs like crap from there on out: loss of power under load or acceleration, sputters and putters. Sometimes pulling over for a minute and letting it idle helps, but not always. During the initial months of ownership and driving I almost exclusively went on local drives without stopping (and therefore, no opportunity for heat sink, at least in the same manner) - just doing a 30 min, or 40 min, or hour long drive and then parking it back in my garage. Consequently, I hadn't noticed or encountered this issue. 

I suspected some sort of vapor lock or fuel pump push-rod issue (the rod binding after the heat soak, perhaps). I did get a gauge on the fuel pump output which indicated an output pressure of slightly over 4 psi at all rpm's- high, but tolerable for Kadron's, I'm told. My fuel lines are rubber with a cloth braiding, but not resting directly on anything other than where they are routed carb to carb forward of, and around the top of, the fan shroud. I did also pull the fuel pump, and the pump base is properly packed with grease and the push rod seems to ride freely within the spacer.

It is my understanding that oxygenated fuels have a lower boiling point than does 'real' gas, and I'm sure that this is exacerbated at higher elevations.  I do have a station not too far away that sells non oxygenated fuel. Would this help? Should I change or otherwise 'insulate' my fuel lines in the engine bay? Help!

Thanks in advance!

- Brent

 

 

Original Post

Thanks, gents -

And Lane, I have looked things over just as you have suggested. I guess that I concluded that since the fuel pump sits right on the case sort of, by default, constituted the fuel lines being 'near a heat source'. 

I just discovered the 'real' gas station this past week, so I'll take Robert's suggestion and give his strategy a go! 

Thanks again!

Remote diagnoses are always risky.  When you examine the circumstances you describe, the only recent variable is higher air temp, assuming you've been at present altitude for some time and your driving habits and fuel usage have not changed. 

The heat soak you describe is common and can have different causes, some or all of which need to be examined separately.  Trying simple fixes first makes sense, such as examining the fuel line completely on its route to the carbs.  Are you sure it's not touching a hot manifold or other heat source?  Correct timing and carb tuning can also affect heat soak.  Some guys swear by the decklid standoff approach, either using a tennis ball as prop or decklid standoff bracket. 

If you do an incremental approach, you need to keep records.  You can get inexpensive remote and/or laser thermometers/heat sensors that will tell you air temp in the engine compartment as well as temp of the block, heads, etc.  I suggest you start by taking temps at various locations prior to trying to fix the problem. Then you have a starting point.  Take a drive, park in your driveway/garage, wait ten minutes, take temps.  Then start with easy fixes first, such as decklid standoff.  Drive, take temps, compare.  Keep doing that until you see definite results.  It's important that conditions are comparable for comparison purposes: time of day, air temp, length and route of drive, etc.

There are LOTS of threads online describing your circumstances exactly.  Samba has some relevant threads that are recent and on point.  When you discover the fix or fixes, please let everyone know, as that's how we all learn.  Best of luck as you move forward.

In my experience, the instant cure for fuel percolation has been to abandon the mechanical "sucker" pump at the engine and go to an electric "pusher" pump up under the gas tank.  I have never seen that fail to work.

Of course, making sure that all of your fuel lines and hoses are at least 4" away from a serious heat source is mandatory to begin with, but a pusher pump will even overcome line percolation simply because it is pushing colder tank gas through the system, bubbles and all.

However, the cheaper fix to try is run your tank fuel down to fumes and re-fill with non-alcohol gas and see if that cures it.  If so, go with that as much as possible.  I also wouldn't choose to run anything more than 10% alcohol gas.

Good luck hunting......

 

As noted, fuel percolation in our cars is a common problem.

It's worst when you stop for a short while after driving hard because the engine compartment is at its hottest then - a few minutes after you park it. The engine is then as hot as it ever will get, but there's suddenly no air running through the compartment, so things like carbs and fuel lines get even hotter than when you're driving.

A quick and painless test is to simply leave your engine compartment lid open when you park to see if that makes any difference. I often do this in hot weather.  I have also insulated some fuel lines that run near the fan shroud, but I don't know if that has made any real difference.

But here's the thing. The effects of this problem (air in carb passages and fuel lines) should quickly go away after you start driving again (within five minutes or so). If they don't, the rough running may be caused by something else. It could be your carbs were never jetted or tuned right for high altitude and that high temps are just making things worse.

It's also possible (but less likely in a new car) that your ignition coil or the electronic module in your distributor are breaking down at high temps and correcting themselves when cool.

Did you tune the carbs (or have it done) after the car was shipped from Arizona? I live near sea level, but drive in the Sierras quite a bit. At elevations above 5000', the car is not as happy as at home. If I'm staying in the mountains for a few days, I'll tweak the carbs a little for the altitude and then reset them when I get home. But if you live at 6000', the jetting, idle mixture settings, and maybe timing should be different than they would have been in Phoenix.

PS: Here in northern California, virtually all gas is 10% ethanol.

 

Here is a website that has the location of all gas stations that offer alcohol free gas. You can look them up by state with a list or map. The octane will differ from one station of another.

https://www.pure-gas.org/index.jsp?stateprov=NC

Wow, I just looked up CA and they are few and far between. They are also mostly 100 or 110. That'd be expensive. There is one station near me that offers 110, but at $8 a gallon, I'll stick to the 93.

Carlos G posted:

Here is a website that has the location of all gas stations that offer alcohol free gas. You can look them up by state with a list or map. The octane will differ from one station of another.

https://www.pure-gas.org/index.jsp?stateprov=NC

Wow, I just looked up CA and they are few and far between. They are also mostly 100 or 110. That'd be expensive. There is one station near me that offers 110, but at $8 a gallon, I'll stick to the 93.

CA does not allow ethanol free gas to be pumped into vehicles. It has to be pumped into containers only. It is supposed to be used in off-road vehicles, race cars, small engines etc only. However it isn't dyed so I'm certain a fair amount finds its way into street legal vehicles. Sunoco SS100 says it is street legal in CA but it is sold in 5 gallon and 54 gallon drums only. You'd have to get it into your street legal car on your own.

Not that anyone would as it is nearly $8.00 US per gallon. The 54 gallon drum price is slightly better but you have to leave a deposit and a cleaning fee for the drum.

i built a good sized deck 10 years ago, used expensive oil based stain on all but the decking, needed to restain but cant get the oil based stain I used in CA anymore, cant get it on internet either..heres the kicker..the old oil based stain cant be repainted with the new water based stain as it wont stick..found out its legal in NV which isnt too far from here..hmmmm..its done and looking new

I've been kind of wondering about that mechanical fuel pump, too.  I'm not a big fan of them, but then on the other hand a LOT of people are running them with no issues (even in SoCal in the heat!) so I wouldn't be the first to condemn it.  

Still, if your fuel lines are well away from heat sources with no drastic high or low spots, your fuel filter is relatively new or known clear of obstructions, the lines are not kinked anywhere and everything looks OK and it still gets heat soak, then it might be percolating the fuel out of the float bowls (I mean, that's all that's left, other than the fuel pump, right?) thereby flooding the engine while sitting/soaking and making it hard to start.  That can often be proved by going somewhere to force the heat soak when stopped, then floor the accelerator and hold it there and then start the engine.  If it is percolated bowl syndrome it should start within 10 - 15 seconds and then probably run crummy for a minute or so until the excess fuel is blown out of the manifolds and then it'll run better.  I don't know why your engine/Kadron combo would do this when others don't, but you could run a phenolic spacer under each carb to insulate it from the head heat - maybe that would help, but no guaranty there, either.

At that point, I would shotgun it and just install a Carter rotary fuel pump up front.

Also, Brent......   Once you get this all figured out I would make it a habit to add "Star Tron" gas treatment to each tank of gas to minimize the effects of the ethanol fuel.  It's pretty good stuff and I've been using it in every tank (and in the gas I use in my yard tools) for years.

***EDIT***  One last thing:  If you want to reduce the fuel pressure by half a pound or so, just add a second (or third) gasket under the fuel pump to shorten the stroke.

Brent,

I'm close to you, Colorado Springs area (6,700'). 2332 engine & I run a electric 'pusher' pump located in the front, below the tank. An advantage is it raises the fuel line pressure, as opposed to the mechanical 'sucker' pump. Raising the pressure increases the boiling temp. It also creates a separation between the hot engine case & the fuel line. Mechanical pumps directly connect the case to the fuel line, increasing heat soak potential. I agree & run non-oxygenated fuel. 

All that rambling being said, I would 1st try changing your oil to lower viscosity. Frozen molasses creates heat.

   10 years living at Lake Tahoe 6900 ft. I have a similar engine configuration. Always had a rotary driven electric fuel pump, Weber IDF 40s tuned for high altitude, same **** gas, poor distribution set set up, never had a vapor lock. I suffered flat spots and shudders for several years until I found a competent mechanic that could properly jet and set the carbs and solve the electric issues. (Shameless plug Anthony’s Auto Werkes in Auburn, CA) I have also learned that even gas from BRAND name gas stations can be bad. I run a can of Seafoam though the engine when I get any hesitating or odd backfiring and it clears it up quickly. 

 

Thanks, everyone for all of the great input and observations.  I'll definitely start with the simplest of solutions and suggestions, and go from there.

I did have the car tuned/adjusted for my elevation immediately after I first took delivery (@SactoMitch) and one of the things that we did then was to add a balance tube between the carbs. The local guys say that it's an absolute must in our thin air and it did in fact make a noticeable difference in how smoothly the car ran.

The 'Star Tron' gas treatment seems to be non-negotiable, and I will definitely make that part of the routine.

I get home tomorrow from a long, exhausting work trip and am SUPER anxious to get back to diddling with the Speedster to get this all sorted out! 

Wait! Did I say that? Correction!! What I meant to say was that "I'm super anxious to get home to the wife and kids . . . . . . .!!!!"

Hi Brent - 

I am in Broomfield now, prior I was in Genesee (7900 ft). When i first picked up my car, it did exactly what you describe - but it would clean itself out after a few minutes. Never really ran *great* however. I did a new pump, a new pressure regulator, insulators and a compufire. Still never ran as I thought it should (my 4 cyl aircooled experience was all 914) .

I threw in the towel and installed a set of 40 Webers. I even ditched the fuel pressure regulator. Car is a different animal now - and I rarely ever need to adjust anything - only/maybe if temps are extreme (I like to go for winter drives). On hot days when I stop for lunch/etc, yes, it still takes a second to fall back into stride after percolating in the heat - but it is minimal. I do not have insulators on them - maybe I should. Oh, I do have an external oil cooler as well as an FYI. Transition from the idle to main jet circuit is also pretty good. This was the absolute best money I ever spent on this car.

Being that so many folks are running Kadrons without issue, I am wondering if there may be a consistency issue with how they are made. I know Weber had this issue for several years.

I do have an older emissions testing machine down at the shop if you want to make sure your mixture is in check. Feel free to drop me a line. I will start spending more time down there starting mid-november.

Thanks, Scott - I'd absolutely love to take you up on that and stop by your shop.  At the very least you could look things over and share your thoughts. I also have an external air cooler, for what it's worth.

I believe that there was another owner here in the area that took delivery of a new VS last spring or summer that went to Weber's, too, but I haven't heard any updates from him.

I'll PM you my cell number. Thanks again!

If you stay with Kadrons, buy a fuel pressure gauge and a stack of ten fuel pump gaskets. I used 7 on a sandrail to drop the pressure from 4 to 1.5 psi. It runs awesome now, not mine, just one I work on. 

Anthony is dead-on correct, any more than 1.5 psi will overload and blow past the float valves.

balance tube between the carbs

30West posted:

Thanks, everyone for all of the great input and observations.  I'll definitely start with the simplest of solutions and suggestions, and go from there.

I did have the car tuned/adjusted for my elevation immediately after I first took delivery (@SactoMitch) and one of the things that we did then was to add a balance tube between the carbs. The local guys say that it's an absolute must in our thin air and it did in fact make a noticeable difference in how smoothly the car ran.

The 'Star Tron' gas treatment seems to be non-negotiable, and I will definitely make that part of the routine.

I get home tomorrow from a long, exhausting work trip and am SUPER anxious to get back to diddling with the Speedster to get this all sorted out! 

Wait! Did I say that? Correction!! What I meant to say was that "I'm super anxious to get home to the wife and kids . . . . . . .!!!!"

Hello Brent, what do you mean "add a balance tube between the carbs." I'm very interested what you find out and solution. I'll be moving to Prescott AZ in Feb 2020 and that area is 5k to 6k in elevation. I'm currently at sea level in SoCal and the VS engine has been jetted for that elevation- measly 190 ft. Thank you, Michael

@DannyP thanks for the fuel pressure guidance. My pressure is way high, and you and several other folks here (in addition to the the guys at KaddieShack) have emphasized the importance of getting this corrected straight away.  Do you recommend putting gasket sealant on both sides of each gasket I add, or just on top and bottom of the combined stack? (I have Permatex #2).

@Michael - in regard to the balance tube, Danny P stated it more accurately. Several,  if not all, of the 'sea level' shops I spoke with (during my build, for example) downplayed it's impact, but the local pro's here at altitude absolutely swear by it. The beauty of it is that it's a simple and inexpensive addition for your mechanic to make. @majorkahuna what did the guys at Anthony's Auto Werkes in Auburn have to have to say about it? 

Michael, I'll keep you posted as I get this sorted!!

It's going to be trial and error...confirm timing , fuel mixture ( too lean - check and " read" plugs) , fuel pressure ( 1.5 to 2 lbs )  balance tube is necessary on the dual EMPI 34's and won't hurt to add it to the Kadrons. Fuel line to heat source issues ? Valves pinging ( rattling ) under load? How hot is the engine getting? Can you pull the oil dip stick and hold it with your fingers ?   If you can't it's running hot. May try propping the rear deck lid and inch or so and see if that resolves the run issue.

Balance tube is a must! On any single barrel carb. 

Fuel pressure regulator installed with gauge rather than shimming the pump. I never had good luck shimming or shorting the pushrod on a stock pump.what I found is under a steady load the pump doesn’t pump enough volume.

dont waste your time. Get a regulator, install balance tube and adjust the accelerator pumps and linkage.

elevation does effect the jetting, but it will never run decent without the basics done

Thank you DannyP, DANNYP30WEST, ALAN MERKLIN and ANTHONY on your input.

I'll have to look for this tube connection sticking out of my EMPI HPMX manifold (most likely it would be plugged- don't remember seeing anything like this when I had removed the top end to change out the air mixture jet. I'll talk with Chris at Air Cooled Only up in Prescott.

Minor update -

Trouble shooting led to identifying my Kadron venturi's as 28 mm (40-28) instead of the recommended 32mm for 1914cc engines (per Jeff Lain @ KaddieShack).  SO, larger venturi's (sp: venturies ?, sorry) and matched jets on the way, along with a 'high flow' air filter kit.  Hopefully this will make a difference at this elevation.

I am planning to tackle the job myself.  Having said that, I'm pretty damn handy, but I'm not a mechanic.  I've recently read "How to Win Friends and Influence People", and I did stay at a Holiday Inn last night, but I fully realize that my charming personality may not be of much value in this situation.  Therefore any advice, insight, guidance, wisdom, free beer. or just general encouragement is greatly appreciated!!

Thanks in advance!

 

Well, first off......    A regular Holiday Inn won't cut it.  Gotta be a Holiday Inn Express - nothing less.

On my 2,110cc with an Engle 120 cam, extractor exhaust, 044 heads and Dell 40mm carbs, Dave at Blackline just dropped me from 34mm venturiis - note spelling - to 32mm versions.  He also decreased the idle and main jets to go along with them and then ran them in on a 1,915cc engine.  

Made a world of difference.  

I'm hoping you see the same results on your set-up - You're heading in the right direction!

Thanks, Gordon! And glad to hear of your success!

Learning as I go, and as frustrating as my car not running right is, I knew going in that this would all be part of the process. Ultimately, I'm grateful for the many things I have learned about the engine and car overall - knowledge that most likely would have never been gained had the thing run perfectly all along! 

High altitude update! The guys at Kaddie Shack shipped the new venturis and jets pronto. I finally had an afternoon last week to get the carbs off of the car and on to the bench. Then, having disassembled everything, I was less than impressed with the original gaskets, SO . . . . . I ordered replacements for those too (and had to wait a few more days for those to arrive).

Perfect timing!! My Mother-In-Law and my gasket kit arrived on the same day! She promptly suggested I disappear into a closet for a few days (I was sure that what she meant to say was ‘garage’) - and so I did!!!

I swapped the 28mm venturis for 32mm’s, replaced the main and idle jets, and nozzle above the float bowl (Jeff Lain says that theirs is improved over the factory original), and put it all back together with what appear to be much better quality gaskets. 

With the carbs reinstalled in the car, moment of truth: the thing fired right up, and actually idled fairly well!! I let it warm up, checked, double checked, and triple checked for leaks, adjusted the mixture, blew my Mother-In-Law a kiss and went for a drive! 

Wow! No more issues! It’s almost like driving a completely different car. Pulls very strong, no hesitation or flat spots!! Really runs and drives well, especially at full operating temperature, whether stop and go, light duty cruising, or at highway speeds.  Apparently what I thought might be a ‘vapor lock’ or fuel boil issue turned out to be a ‘breathing’ issue. I am super excited to be able to get back to just enjoying my car! Thanks to everyone who offered input and advice!

Final note: a guy beside me at a stoplight rolled down his window, looked at my smooth running Speedy, then asked me why I had such a big smile on my face.

I answered, “Because my Mother-In-Law is in town”!!!!

 

 

Finally, just an additional thought about Kadron carburetor’s:

I have read here on the SOC site and heard from a variety of other sources issues with the quality (and quality control) Kadron’s. I mentioned the questionable quality of the original gaskets in the post above, but here is what I found holding the throttle body to the ‘main’ body of the left carb:

The screw pair on the right is correct, with the head fitting nicely into sized recess when installed. The pan head screws on the left are, by all accounts, incorrect.

20609C08-6AE0-48B1-AC88-8947D7DAAE37

I opted to replace all four but finding replacements locally seemed to be a bit of a challenge. Impatient and wanting to get the car back together I opted to use screws with properly sized threads (and length), put the new screws in my power drill, walked it over to the bench grinder, gently ground the heads down a bit to the proper diameter, and voila!

The new (dark) gaskets can be seen in the foreground, with the original gaskets behind:

9639BA1C-2EA5-499E-87DF-0591636B62BF

Just a few thoughts, and learning as I go! Thanks again for all of the great advice!

- Brent

Attachments

Photos (2)

@30West- The only thing you may find, Brent (and anyone else out there running Kadrons), is with time you may notice a couple of things-  the carbs getting a little less responsive to tuning and them tending to run a little lean being the first. This is from the throttle shafts running directly in the carburetor bodies with no bushings- the fix is to get someone to bush the bodies. The 2nd issue that rears it's ugly head with time- the linkage joints wear. I believe you can buy replacement pieces. 

In spite of the criticisms you'll read online, Kadrons are a fairly simple, reasonably well made dual carburetor kit with much better fuel distribution (and cooler running) than any centrally mounted carburetor. I wouldn't do the re-work necessary for really big engine power but for a mild up to 2 literish engine they do work well.

Add Reply

Likes (0)
Post Content
×
×
×
×
×