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Discussion Starter · #1 ·
Hey guys, I have a small problem with my idle. I have a recently rebuilt 1.9 CIH that is still being broken in. Has a Weber 32-36 carb, flat top pistons, mild cam upgrade with the OGTS small header. It runs, starts and idles very well EXCEPT after a long drive at highway speeds. It will then just die at stops. Feathering the pedal will keep it running. I have tried multiple different settings as far as idle mixture and speed with no help. I am wondering if the heat from the header could be cooking the intake manifold and causing the problem. Have any of you had this trouble? I am considering either header tape or a heat shield to see if it would help but before spending the time and money I am hoping to hear from the voice of experience.
Any advice?
 

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The Young One
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I don’t think it would be the header because the stock exhaust manifold was bolted directly to the intake and that would cause more problems then a header. The header would make the heat go away more.

Also is it overheating and how is the temp of the engine?
 

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Discussion Starter · #5 ·
I don’t think it would be the header because the stock exhaust manifold was bolted directly to the intake and that would cause more problems then a header. The header would make the heat go away more.

Also is it overheating and how is the temp of the engine?
Temp is fine, new alum radiator and temp sensor.
 

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Can Opeler
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Check the brake booster hose for leaks. Pump the brake at idle and see if it dies.

Also I don’t know how this works, but I had an issue with valve lash that caused this on my first engine. After adjusting the valves and nothing else I never had the issue again. Could be a coincidence, but idk.
 

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Discussion Starter · #7 ·
Temp is fine, new alum radiator and temp sensor.
Check the brake booster hose for leaks. Pump the brake at idle and see if it dies.

Also I don’t know how this works, but I had an issue with valve lash that caused this on my first engine. After adjusting the valves and nothing else I never had the issue again. Could be a coincidence, but idk.
New booster and hose. If that was the problem it would happen everytime the brake was applied at idle anyway.
Good guess though!
Valve lash, Hmmmmm
 

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I’m just going through my thought process, if your understanding of the choke adjustment and lean best idle set up is good ignore my post. Just a piece of the checklist to say it’s possibly choke related?
 

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Discussion Starter · #14 ·
I’m just going through my thought process, if your understanding of the choke adjustment and lean best idle set up is good ignore my post. Just a piece of the checklist to say it’s possibly choke related?
No, the choke is working as designed and is set from the factory. This problem happens well after warm up. I have played with the idle mixture adjustment from lean to slightly rich. No effect. Like I said it will idle and run great in town. It seems to happen after an extended highway speed drive. I downshift to a stop and it just dies almost like the ignition is shut off. It can't be lack of fuel because I can feather the accelerator pedal to keep it running or pop the clutch to restart or place in neutral and brake with my left foot while slightly depressing the accelerator to up the idle. I am really at a loss. No vacuum leaks. The throttle linkage seems to function just fine.
 

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Maybe the butterfly shafts in the carb leak a little air when hot. They don’t make them like they used to. Easy test, spray around the butterfly pivots when hot and see if it has any effect on the idle.
 

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How far in is your idle speed screw from initial contact? What happens if you use it to keep your engine going under your stall conditions with the warm engine? Forgetting the lean best idle procedure for now, giving it an extra full turn in or so can you keep your engine going at idle? Then with the warm engine restart it under the conditions that it doesn’t stall. Does it race? Of course the choke butterflies should be always fully open when it’s warm. I’m not sure how accurate the factory setting is although they’re usually good in my experience, but as with all things in life not always.
The fact that you mentioned that the mixture screw has no effect makes me wonder how it’s set up?
 

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Discussion Starter · #18 ·
How far in is your idle speed screw from initial contact? What happens if you use it to keep your engine going under your stall conditions with the warm engine? Forgetting the lean best idle procedure for now, giving it an extra full turn in or so can you keep your engine going at idle? Then with the warm engine restart it under the conditions that it doesn’t stall. Does it race? Of course the choke butterflies should be always fully open when it’s warm. I’m not sure how accurate the factory setting is although they’re usually good in my experience, but as with all things in life not always.
The fact that you mentioned that the mixture screw has no effect makes me wonder how it’s set up?
Sorry, the mixture screw will affect the idle when setting the mixture, it just doesn't stop the problem no matter if it's lean or slightly rich. The idle speed screw is less than maxed out. If I set the idle speed up to 1500 it does not die but I can't stand that high of an idle. The crazy thing is that small adjustments of the idle speed screw have no effect on idle speed. The more I ponder the situation I am beginning to think something is wrong with the butterfly valves, possibly loose or binding on the spacer. I have had nothing but problems with this new Weber. First, the float valve was shot right out of the box and I had to replace it. The choke butterflies were sticking and would not close when cold and flooring the gas pedal. I found that if I loosened the butterfly screws a bit they worked fine. I may pull the carb tomorrow and inspect the primary butterfly for some malfunction.
This is my first experience with Weber and so far I am not a fan.
Just an FYI, I was a Volvo Master Tech for 30+ years so I am not a newbie. Thanks for the advice!
 

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I had a bad brand new out of the box 32/36 DGEV (yes genuine) & sent it back, too lean on the primary, they made good & sent me a new one. It corrected the problem.
Yeah if you have it set up right and still have trouble.
It sounds like you’re on to your problem.
 

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Put a fuel pressure gauge on it. I know you say the fuel pump is "stock mechanical" and is new. But, in the Chevy world, you almost cannot get a "new" fuel pump with the correct spring. The spring determines the pressure. The morons designing the new pumps use "more's law"; Just in case you never heard of it, "more's law" says: if some is good, more is better. It is usually relegated to camshafts, but can worm its way into everything (but I digress).
When they use too stiff of a spring, it increases the fuel pressure. I would not be surprised to see this philosophy creep into manufacturing for other makes.

I had a "stock mechanical, new" fuel pump on an El Camino a few years ago. It behaved exactly as you describe. I put a fuel pressure gauge on it, and it was over 11 psi. It just overwhelmed the needle and seat. I swapped to a low pressure (4 psi) electric pump and have had no issues since.

Not saying it is fuel pressure. Just saying check it.
 
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