Need some help - Drclock is stumped, engine issue .

Only thing I can guess is maybe bad #1 & #3 wires (or plugs). Unlikely, but easy to check if you haven't done it. Or maybe swap back in a know distributor?

I've done that too.

fuel line to #1 & #3 carb?

Spark plugs gapped properly or wrong type. They could be fouling or not even firing. Just a guess.

Two single barrel carbs supply 1 & 2  -  3 & 4 

All four plugs gapped correctly and are new .. replaced  twice.

Real puzzler. I've seen brand new Kadrons with a split emulsion tube or missing air passage brass plug cause one side not to respond to mixture settings.  But, you've switched the carbs and didn't see any difference, that is not the problem.

Is it possible that both carbs are running really lean (jets?, filter? pump?)? Perhaps the front to back runner differences would cause 1 &  3 to be leaner than 2 & 4 under very lean conditions?  I keep coming back to carbs, but the 1 & 3 is puzzling.

You know that I’m clueless, but valve-related?

You say you switched out the distributor a couple of times but with either did you pull the plug wires off each of #1 and #3  ( leaving the plugs still installed ) and attach a new plug to each wire and look to see if you get spark while someone else turns the engine over ? 

You flipped sides with the carbs with no result, so it’s not them, but did you flip the intake manifolds with the carbs or leave the manifolds in place and just flip the carbs?  I could suspect the intake manifolds or gaskets.

Is compression # now the same on all four cyls?

Is the idle even at 800-ish or does it look ragged?

Is there an obstruction in the fuel line for #3 & 4?  (I’m reminded of a piece of laytex glove in mine)

When you remove a plug wire and nothing happens at idle, what happens if you rev it?  Does it spin up roughly?  Does it spin up better with all plugs/wires connected or act the same on acceleration with #1 & 3 disconnected?

I keep suspecting the intake manifolds or gaskets, but.....

What is the alternator voltage output when you rev it up?  When you went from generator to alternator did you wire the old regulator by-pass right?

That’s all I’ve got right now.

Yes checked spark it's good at all plugs

Compression same on all "new"  four cylinders

Idles fine and revs fine on test stand

It's not intake / gaskets these were carefully rechecked visibly with carb cleaner and even sanded the intake and carb bases with emery cloth across a piece of glass in a figure 8 pattern (old school method) 

.........Interesting re: alt volts I  will check

And BTW we pulled the used exhaust off to see if there was dead occupants or remains there of.

Alan Merklin posted:

... re-measured cam op (exhaust valves open & closed with dial indicator all specs as new) 

The fact that 1 and 3 share symptoms tends to make me think this is a cam issue. As you know, it’s either spark, fuel, or mechanical. You’ve swapped carbs side to side, and the problem persisted. You’ve paid a lot of attention to the ignition, without success.

You seem to be saying that you checked the exhaust valve with a dial indicator. Did you by chance check the intake?

Stan.. I'll rule out mechanical as most components are new.  Yes cam checked all lobes intake - exhaust and at specs ..   Since the engine is on a run stand a 140 miles from me we are going back and forth checking the boxes. The builder is going to test swap the duals carbs for a used stock manifold and Solex and see what happens.   I've com across some really strange issues over the years but this one tops it all.

Wait.....You live in West Virginia.

How strange can this really be?    

Nothing wrong with West Virginia, great mountain scenery,  good hearted people, ready to welcome you,  lend a hand  and have a deep rooted pride for family, God and country. Like everywhere else some people make poor life choices but all in all it's the best state I have resided in.

uhm, is there gas in the tank?

barncobob posted:

uhm, is there gas in the tank?

Currently mounted to a engine test stand

When you switched from gen to alt, did you change fuel pumps old style to new?

Sacto Mitch posted:

 

When you switched from gen to alt, did you change fuel pumps old style to new?

 

Yes alt. pump and correct rod ~

I think it's your carbs. Change back to the carb you had before since it's on a stand and see what happens..........Bruce

Single barrel Empi 34's supply two cylinders but that's the next step in this process, remove the  Empi 34 baby Webers ( Had good luck in the past) and reinstall the single Solex and stock manifold. The fact that it's the front left and right cylinders ( 1 & 3 )  it's trying to tell me something. 

I have never used those carbs but others I know have and had weird things go on with them, similar to what your experiencing......Bruce

I know how frustrating this can be. I solved my problem once by removing the oil dip stick and reinserting it into a new engine, my problem was solved. I'm wondering WWCVD ( What would Cousin Vinnie would do).

How about the ground to the spark plugs?  Testing them out of the engine, ground is good and in the engine, thread lube or anti seize is not allowing a consistent ground?  Just a random guess after all of the info and data above.... Good luck with this one! 

You know, somewhere in the back of my mind I remember hearing about something like this happening to someone else - like the engine idles on 2 cylinders but acts normally when you rev it or under load.  Don’t know if they used baby Webers or Kadron single throats, though, and there was no clear solution, other than swapping out the carbs to something else, which is where you’re going.

Do those mini-Webers have brass thingies by any chance?

Double check plug wires with respect to firing order. Yes, even an old salt can make a mistake once in a while. Rocky did this on Max's car and it took Lenny, Max and I a while to figure it out. We assumed it was correct......

Oh we're way past the firing order, so far one of the two new carbs are junk, the mixture screw adjustment is erratic ...the only thing we can come up with is the carb has an internal casting screw up. But still figuring out one other issue.....stand by ~

I’m still betting on a brass thingie of some kind.

Alan Merklin posted:

Oh we're way past the firing order, so far one of the two new carbs are junk, the mixture screw adjustment is erratic ...the only thing we can come up with is the carb has an internal casting screw up. But still figuring out one other issue.....stand by ~

Progress. That's great news

EMPI carbs. I'm not surprised, but I'm glad you're getting to the bottom of it.

The brand new Brocar carb I put in the 1600 last year would not run at idle. Almost any idle. I could rev it non-stop to keep it running. It turned out that the idle pilot, (not the idle bypass or adjustment) screw was bottomed out and not allowing idle fuel into the mixture. This is the tiny screw that is mostly hidden on the right side of the carb body.  I had to spin down a tiny washer to “space” that pointed screw out of the fully seated position. I read about the issue on The Samba site. Many hours were wasted trying to adjust a very simple carb! Yikes, the MADNESS was present! Let’s make all of our replacement parts in third world countries where quality control has no meaning! ;-0 

One of the two guys I know who had problems with those carbs said that the passage for the idle circuit was non existent. The other said that the transition ports were not drilled in one of his carbs.  I don't know which it was but he said that the threads for the fuel line connection were stripped or not threaded as well. That part was fixed but the other issues clinched the rejection of the use of the carb set.

On another note. One time I replaced a turn signal switch assy. because of some reason I don't recall but when I installed the new switch and wiring harness, I stripped and grounded out the same wire in the new harness. Of course you KNOW the NEW assembly IS GOOD ! After a couple days of struggling with this same problem, you start changing everything else to no avail.  The shotgun approach !  Even that didn't get results. SOoooo.......I handed the job off to another guy. He did the proper diagnosis and determined that there was a grounded wire. Replaced the Switch assembly, and everything was fine !  The new switch I installed had the same wire skinned as the original wire. I ate crap for a while from the other guys..........Bruce

@AIRCOOLED you hit the nail on the head  i.e idle circuit passage and the transition ports were not drilled in one of the carbs..that totally makes sense with my issues..  I am going to order a good dual Weber 34 kit and be done with this..... thanks!

It wasn't me....I just knew someone that had similar problems. They figured it out.  I just paid attention.  I'm just glad you found a definitive source of your symptoms. It can be very frustrating sometimes. A plastic sandwich bag floating around in your fuel tank will drive you nuts too !!  How bout diesel fuel in the "cold start" gasoline tank on a Propane fueled truck ?..........Bruce

A few responses were spot on ( Thanks! ) and helped to resolve this two fold problem.   It juts baffled me that one side would not respond to a mixture screw adjustment and at idle # 1 and # 3 would not drop off in rpm's when those plug wires were pulled....  Be as it may and with poor Chinese workmanship, the  idle circuit passage and the transition ports were not drilled in one of the dual EPC 34 carbs.  Also because of a poor design the 1 and 3 cylinders are getting a very lean fuel mixture at idle.  Confirming that was easy, we bolted up a VW stock manifold single stock carb and it hummed along . I'm getting the one bad carb replaced under warranty. In many past applications I have had good luck with these EMPI  EPC single throat dual carbs, but I am so done with them.  BTW the Weber ICT 34 is the same thing...I would not suggest using these carbs . After doing a lot of research I would suggest two stock VW carbs on shorty manifolds with the twist linkage.

Doc, i’m Putting Weber kits from CB perf on my new motor. Are they the carbs of which you speak? Do I need to worry about this step of the assembly? I have been dealing with rocker arm geometry for two weeks. Ugh!

Are they Weber 34 ICT's?  IF so there are quite a few of those and the Empi EPC 34's that have internal casting issues,..... idle circuit passage and the transition ports not drilled properly.  Also, the bottom of carbs and manifolds the surfaces are no exactly flat and have to be sanded by using a emery paper on a piece of glass in a figure 8 movements to get and exact flat surface. The throat on the carb where the cone air filter is clamped is tapered after the engine gets hot a few tomes the air filters slip off. Also there is no room the bottom manifold too head studs to get a wench on a 11mm nut so that area needs a light grinding to make room for a wrench or socket.

Glad you solved the mystery and have given a heads up to everyone on the board. Nice sluething!

Thanks Alan. I’ll most likely be digging into this situation this weekend.  Sounds like it may be another challenge.