My old pickup with a /6 is driving me up a tree. I have had two different holley carbs on it, with the last from a running engine that did NOT whistle or have any of the other problems I am having now.

Replaced the leanburn system with a chrome chrysler pack style ignition and single pickup distributor whose shaft turns nice and smooth with no slop.

New coil wires, coil, ignition pack, plugs, fuel filter, etc...

The engine is hard to start, kicking back occassionally like it is out of time. The timing is spot on at 12 BTDC, but I have had it everywhere from TDC to 20 BTDC and the backfire and whistle remains. Disconnect the vacuum advance and the engine changes rpms so the advance is working. Gear on the bottom of the distributor is clean with no signs of wear. Once it starts and is warmed up it will idle for a few minutes, but then slows unitl it dies.

Put it in gear and it runs rough. Give it gas while it is gear and it will start backfiring through the carb with no power running very rough.

Give it gas suddenly while in park and it will backfire once through the carb, but only once.

Adjusted the valves and readjusted them. Backed off until they were all clicking just to see if the backfire would disappear. Set them all spot on perfect gap. Same problem.

Thought it might still be the carb so I doused it with Penetrating Oil from all sides a few times paying particular attention to the throttle shaft. No change. Checked, rechecked and changed out the extra vacuum fitting plugs. Same again.

Turned the fuel mixture screws in until it ran rough, then backed off 1/2 turn each. Same problem. Backed them out 1/4 turn until it was pouring fuel in and still it backfires, stumbles, etc... Leaned it out and same again.

Looked down the carb while working the throttle. Nice solid squirt of fuel from each bore each time.

Tested the chrysler chrome ignition pack pin 5 to ground and that is good. Tested Coil primary and secondary windings on two different coils and both are good. Two different carbs and the problem continues. Tested the ignition pickup coil in the distributor and it is fine. I don't have a vacuum gage but if you suck on the distributor vacuum hose while it is connected to the distributor it holds a vacuum for as long as you like. Two different distributor caps, rotors etc... Even tried reversing the pickup coil leads to see if that was the problem since I read here that this can cause a similar problem. Yup, they were right. It actually ran worse. That was not the problem so I put it back the way it was supposed to be and tested the pickup coil again. 230 ohms which is way inside the margin.

Dropped the exhaust at the front of the muffler (nothing else to restrict it) to see if the muffler was maybe clogged and causing problems. No dice.

I had a transmission fluid leak at the front seal and pulled the engine to replace the seal (still leaking at the front so I figure the tranny pump is to blame since the throttle kickdown was wired midway with the kickdown rod missing when I bought the truck. I installed the right kickdown but I figure it was too late).

Removed the intake/exhaust manifold while I had the engine out so I could replace the freeze plugs since one showed signs of a water dribble. Did NOT separate the intake from the exhaust while I had it off since it did not exhibit any problems before hand. Replaced a broken stud on each end of the manifolds, cleaned the mating surfaces, put in new gaskets and bolted it all back up.

That is about it. Runs like KaKa. I am figuring it is one of a few things. Leak at the baseplate of the carb (Tried two different new gaskets there but figure maybe the surfaces are irregular), leak at the intake to head mate surface, leak somewhere in an intake runner or maybe a combination of the above.

I don't think it is a burned valve because it should be popping all the time instead of just when it is in gear or being romped on.

For the same reasons I don't see how it could be the timing chain because I have had the distributor all over the place with the advance on and/or off and it still does it.

I am just not buying the idea that it is doing this because it is a "bad Holley carb" since the same condition prevailed with two different holleys AND the last one I put on came off a running V-8 with no signs of anything I am seeing now.

Now if I cup my hands over the carb the whistle goes away and this was on both carbs.

What is really bugging me is when I crank it and it suddenly stops like it is out of time, like it is trying to backfire. Not sure why and I figure this is where I am missing something and likely the root of the problem.
I have checked the timing and reset it so many times I can do it in the dark though. Checked the firing order. Verified the wiring pattern, pulled the distributor and checked the pickup coil, cap, rotor again, set it on #1 TDC and did it all over again and again and again, etc... That timing line chalked and not jumping around like they do when you have a sloppy timing chain.

Now before I go out to work on it with an attitude of "tighten up the bolts until it is fixed or something snaps I wanted to check in here to see if anyone see's anything I missed since I have done it so many times I figure I will keep making the same mistake over and over again.

George

PS - I know this is really long but I used it to review and see if I could spot anything wrong. Still lost

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Lead, Follow Or Get The Hell Out Of The Way!

Disconnect the vacuum advance and the engine changes rpms so the advance is working.

This caught my eye. Is your vacuum advance connected to a full-time vacuum port, or is it connected to ported vacuum? Backfire through the carb usually indicates a timing issue. You have some vacuum even when starting, so it sounds like your way to advanced on your timing.

First connect that Dist to Venturi Vacuum. Warmed up at idle, the rpms shouldn't change since there shouldn't be enough vacuum to advance the timing AT IDLE.
Second try some Dr. Ben Casey technology.
Taking a long /6 vacuum advance hose, put one end just in your ear and move the other end around the base of the carb. Listen for the whistle or a loud hiss. The point you made that the whistle goes away when you choke down the airhorn of the carb leads me to believe you have one hell of a vacuum leak.
Third I assume from your post you have a 500 - 4412 Holley?
Check all the adapters and gaskets it mounts with for the vacuum leak.
Terry

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Terry Bogusz
From Super 6 Left turns to Straight again.

That's what I was talking about. Was too close to the problem to troubleshoot right. Moved the vac line to the right source. Thank is another problem that I don't have to chase down.

Still has the same original problem, stumble, whistle, pop, etc... so I will be using your listen for leaks suggestion tonight.

Yup, 4412 carb. Clean as a whistle (Pun grudgingly intended, yes... I am that twisted). I can sit it back on the engine it came from and there are no problems. Drop it back on the truck engine and "Wheeze, whistle, pop!"

Can these things leak from exhaust to intake through the warming pod beneath the carb?

Anyway, I will be looking into that whistle using the vac hose tonight after work. Thanks.

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Lead, Follow Or Get The Hell Out Of The Way!

If you are using a Mr. Gasket (1937)adapter plate to get this carb to mate to the intake, then you have to dope the bolts(and heads in the recessed areas) and use a ring of sealer around the edges of the mating surfaces, the gaskets that come with the carb and kit don't seal so good....also if you have a late enough truck (since you said lean burn...), you might want to pull the EGR and regasket it and flip it 180 degrees to disable it so the heat of the exhaust in the manifold doesn't cook the sealer either (or plate the EGR off)...and yes, if the manifolds aren't mated right, or off different "Stacks", or just warped they can leak from the spot where the manifolds mate up...

That will get you closer to getting rid of the phantom vacc. leak/whistle...





http://www.slantsix.org/forum/viewtopic ... olley+2300

-D.Idiot

Have you tried a different ECU on it? (Elect. Ignition control unit)

I had this type of problem a while back and it ended-up being a bad (new) ECU.
Hook-up a timing light to the coil lead and watch it during miss-fire & popping, the light will be sporatic - miss pulses if it is a bad ECU or an ignition problem.
DD

It was the timing chain

Thanks for all the advise. I actually did find a number of other issues that would have been overlooked if I had not asked here.

You guys Rock!

George

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Lead, Follow Or Get The Hell Out Of The Way!