Hey y'all,
I've finally got my project C3 running, but the engine dies whenever I come to a stop. I haven't ever taken the engine apart and the previous owner didn't make a sheet, but it does at least have an aftermarket cam and a Holley 0-6210 carb. I don't know if it's the autozone special or a built 383, so I can't describe that. It is a 4-spd manual.

When coming to a stop, the engine will drop to about 500 rpm, then surge back up to around idle. Then when I'm at about 5/10 mph, the engine just shuts off unless I flutter the gas pedal.

Would this issue be due to a fuel delivery problem, way to aggressive cam, etc.?

 

I'm going to go with fuel delivery. Floats misadjusted, dirty passages... does it run fine at a cruising speed and accelerate as expected?

 

Yes, it runs like a dream above 15 miles an hour. It may be the floats, but I just redid the carb and set them. Maybe the sending unit? Any way to check without dropping the tank?

 

I would check timing. Make sure the vacuum advance is working. Then readjust the idle set screws and idle
Then you would have to recheck the timing and idle adjustment.

 

How exactly would I check? I have a vacuum gauge, would I hook it to the carb or distributor? What level am I looking for?

Also, how to you adjust timing on HEI? Just unbolt and twist with a timing light or is there a special way to do it?

 

with engine off, checking the vacuum advance can > use the vacuum pump, remove the distributor cap just enough to see advance arm, connect vacuum pummp to the vacuum advance can nipple and pull a vacuum, you should see the arm move.

HEI is the same as the regular distributor > connect the timing gun sensor to the number 1 spark plug wire. Connect the positive to a positive source, I usually use the output of the alternator, find a good ground and connect the ground.

adjust your timing so that you are reading your base timing with the vacuum advance disconnected and the idle at your desired level. My motors like 14 degrees initial usually. If you havent investigated your timing before, you should contact Lars here on the forum for his timing papers for adjusting your timing for base timing, then adjusting your advance so that you have 36 degrees of advance before 3000 rpm. You would just be using mechanical advance plus your initial timing. After that is set you would recheck you base timing and that would be your new initial timing. Mine is usually right about 14 degrees before I start using a Computer controlled EFI with timing control. After that you reinstall the vacuum advance, readjust your idle then recheck your timing andn see how much you have at 3000 rpm. If the vacuum advance gives you more than 48 to 50 you would need to add a limiter to the vacuum advance. Its a small plastic washer that comes in the vacuum advance spring packs different ones of different sizes to change the limit amount.

Like I said, Lars' paper is more involved

 

As @Rescue Rogers said, get a timing light, and a copy of Lars' papers.

Here's a quick video on how to time a Chevy. They use timing tape (which is a great idea), or you can use a dialback timing light (like an Innova 5568).

Your immediate problem could be as simple as moving your vacuum advance from ported to manifold vacuum on your carb, but you'll want to check timing anyway.

 

Make sure your vacuum advance isn't connected to ported vacuum.

 

In addition to what has been posted.....do you have any vacuum when you open the gas cap to fill up? Probably not the issue but worth a question.

More of a concern to me would be... How old is the gas?

 

Recheck/reset your carb float level. Also, is the float itself in good condition?