63, Engine dies when clutch is depressed

[Steve D.]

63, 327_340, Edelbrock 4105 carburetor, non-electronic distributor with points, lt1 cam



I recently had a saga of "engine dies after warm up" that many of you participated in. That got solved by insulating the fuel line from the pump to the carburetor. Now I have another "engine dies" problem, but different circumstances.

After warm up, when in motion and the clutch is depressed for cornering or stopping, the engine will die. The engine will restart easily and idle well. If I am stopping and the engine starts to die, I can give it gas (fast footwork) and prevent it from dying, and once I am stopped it will idle fine. Someone suggested that I check the adjustment of the carburetor floats. I had occasion to do this fairly recently during the previous saga, so the float adjustment should be OK.

Any other ideas?

Steve

P.S. I checked the archives, but the only post I found with similar symptoms had TI distributor problems. A generalized Google search turned up a number of posts describing my same symptoms in several different more modern makes and models. And curiously enough, a neighbor with a Factory-Five GTM kit car, which is built with a C5 engine and drive train, has the same problem.

[Edward J.]

Re: 63, Engine dies when clutch is depressed

Steve, you have some sort of fuel issue with the Carb. as it sounds, What I find is with ethanol fuel is the higher the float bowl temp. gets the higher the float level in carb. gets. I had a similar problem with my 63 AFB carb. I lowered the float 2/32ths from the factory spec. the next time you have the problem just look in the throat of the carb. and see if there is fuel dripping. this would be a sign of a high float level or a heavy float.

[Rich G.]

Re: 63, Engine dies when clutch is depressed

I think Edward is on to something. In addition be sure the secondary is not dripping. My 68 has those symptoms when one of the secodaries is dripping because a a bit of dirt.

Rich

[Mark E.]

Re: 63, Engine dies when clutch is depressed

Why would this only happen when the clutch is depressed?

A long time ago, I purchased a thoroughly used '73. During the test drive the courtesy lights turned on when the clutch was depressed. That problem helped me negotiate a good price.

Root cause: The dash wiring harness was so butchered up with repairs and modifications that the clutch pedal touched an exposed wire when depressed. This somehow completed the courtesy light circuit. Remedy: New harness.

[Steve D.]

Re: 63, Engine dies when clutch is depressed

Edward

You and Rich both mentioned dripping in the carburetor. Is the suspected problem that the engine is dying from too much fuel?

Steve

[Duke W.]

Re: 63, Engine dies when clutch is depressed

63, 327_340, Edelbrock 4105 carburetor, non-electronic distributor with points, lt1 cam





After warm up, when in motion and the clutch is depressed for cornering or stopping, the engine will die. The engine will restart easily and idle well. If I am stopping and the engine starts to die .

I don't understand: Why would you depress the clutch for cornering? You should enter a corner in the gear needed to exit.

I had a similar problem with my erstwhile '84 MBZ 190E 2.3 with the Bosch KE-Jetronic fuel system, even though I downshifted approaching a stop. The problem was particularly acute when the A/C compressor was engaged. Mercedes didn't know what to do. It was probably deserving of a recall...

In any event I solved the problem by modifying my driving habits. When approaching a stop in second gear I would typically declutch at about 1500, but I modified that by not declutching until the engine was close to the 700 idle speed, typically less than 1000, and this cured the problem.

Does your engine have a low mass flywheel? If so that could be an issue.

Too low engine idle speed could also be an issue. Some guys try to idle high overlap cam engines so low that they are on the verge of stalling. I recommend about 900 for the LT-1 cam.

Duke

[Mark E.]

Re: 63, Engine dies when clutch is depressed

Edward

You and Rich both mentioned dripping in the carburetor. Is the suspected problem that the engine is dying from too much fuel?

Steve

An uninformed guess: Maybe the carb is too rich, with the symptoms worse when warm (less tolerance for rich air/fuel), the fuel is sloshing about in the bowl (cornering, stopping), and the clutch released with no throttle (less air). Double check the buoyancy of the float, the float level, and operation of the needle/seat.

Failing that, install a known good test carburetor. (Every vintage car owner should have at least one. ) This may save a lot of troubleshooting time.