C2 Stalling

[Patrick M.]

I completed total body and mechanical ( new correct cam,valve train, aluminum radiator, recommended VAC, rebuilt distributor and carburetor wires and plugs )restoration of my '64 SHP roadster in '06. Thanks to a lot of help from Duke and many others I was able to achieve relatively smooth idle with temps 180 - 200, good acceleration, reasonable mileage and no stalling. I drove the car weekly until my wife became ill in December '06.

Until recently I've driven the car only a few brief times. On my first extended outing the car stalled after 20 munutes of driving and continued to stall at every stop. To restart I had to pump the accelerator.

I drained the gas tank, refilled with fresh 93 octane ( 10% ehtanol ) and rechecked and reset dwell and timing. Total idle timing is 30 degrees and 50 at 2350 RPM. Also adjusted idle jets for maximum vacuum, constant 12". Running much better I've been out several times but the stalling after 20 - 30 minutes continues.

Should also mention all new fuel lines, corectly located and with rebuilt fuel pump.

Please help before I'm run over by the very impatient Florida drivers.

Thanks,

Pat McInerney #37445

[Donald T.]

Re: C2 Stalling

Pat,

Have you checked and adjusted the float level in the carb? Perhaps a sticking float?

[Joe C.]

Re: C2 Stalling

I completed total body and mechanical ( new correct cam,valve train, aluminum radiator, recommended VAC, rebuilt distributor and carburetor wires and plugs )restoration of my '64 SHP roadster in '06. Thanks to a lot of help from Duke and many others I was able to achieve relatively smooth idle with temps 180 - 200, good acceleration, reasonable mileage and no stalling. I drove the car weekly until my wife became ill in December '06.

Until recently I've driven the car only a few brief times. On my first extended outing the car stalled after 20 munutes of driving and continued to stall at every stop. To restart I had to pump the accelerator.

I drained the gas tank, refilled with fresh 93 octane ( 10% ehtanol ) and rechecked and reset dwell and timing. Total idle timing is 30 degrees and 50 at 2350 RPM. Also adjusted idle jets for maximum vacuum, constant 12". Running much better I've been out several times but the stalling after 20 - 30 minutes continues.

Should also mention all new fuel lines, corectly located and with rebuilt fuel pump.

Please help before I'm run over by the very impatient Florida drivers.

Thanks,

Pat McInerney #37445

Patrick,

I assume the carb is a Holley 2818, or similar? If so, then remove the sight plug in the primary float bowl. Have rags below the open hole to absorb any spilled fuel. Have an assistant monitor spillage, and have a dry chem or foam type fire extinguisher at hand.
Start engine. Fuel should just barely dribble from sight hole while engine runs. Shut off engine. Fuel flow should stop, and not continue to run out of sight hole.
Be sure that your idle fuel pressure is between about 4 PSI, and NO MORE THAN about 7.5-8 PSI.

Joe

[Duke W.]

Re: C2 Stalling

Good previous advice.

Infrequent driving can cause problems since most of the fuel evaporates from the bowls between drives, and it often leaves behind a syrupy residue, which eventually hardens into a varnish. Take an ounce or two of fuel, put it in a small glass and leave it outside in a safe place and see what's left after a day or two. You'll get the idea.

This can upset idle/off idle fuel metering due to deposit buildup in the tiny air bleeds and emulsion passages that are part of this idle/off-idle system.

Adding a bottle or Techron or other fuel system cleaner might help.

... sounds like your spark advance map is right on the money, but your idle vacuum is higher than I would expect for a 30-30 cam. You didn't install a LT-1 cam, did you? Well, I can't blame you for not admitting it to avoid suffering the indignation from the 30-30 cam police.

It could also be a percolation issue. Make sure the heat riser valve is open, and I recommend wiring it to full open so it never closes. Often the valve will close at idle and in hot weather this can lead to fuel percolation, and an overly rich mixture that can cause the engine to stall.

Duke

[Joe C.]

Re: C2 Stalling

Good previous advice.

Infrequent driving can cause problems since most of the fuel evaporates from the bowls between drives, and it often leaves behind a syrupy residue, which eventually hardens into a varnish. Take an ounce or two of fuel, put it in a small glass and leave it outside in a safe place and see what's left after a day or two. You'll get the idea.

This can upset idle/off idle fuel metering due to deposit buildup in the tiny air bleeds and emulsion passages that are part of this idle/off-idle system.

Adding a bottle or Techron or other fuel system cleaner might help.

... sounds like your spark advance map is right on the money, but your idle vacuum is higher than I would expect for a 30-30 cam. You didn't install a LT-1 cam, did you? Well, I can't blame you for not admitting it to avoid suffering the indignation from the 30-30 cam police.

It could also be a percolation issue. Make sure the heat riser valve is open, and I recommend wiring it to full open so it never closes. Often the valve will close at idle and in hot weather this can lead to fuel percolation, and an overly rich mixture that can cause the engine to stall.

Duke

Well, OKAY Duke, I let it go, but I saw it too! His lash is probably set too wide, to give him such high idle vacuum readings. It'll make his engine idle smoother, give it slightly more low end torque, but cut his top end power. In short, it'll act more like an LT1 cam. He doesn't state what RPM it was recorded at, but any 30-30 cam worth it's salt, and adjusted per your super-duper .023" lash settings, should yield no more than about 9.5 in-hg @ about 850 RPM.
He probably has the LT1 bump-stick installed, but won't admit it. That's the reason that the engine is running badly! Can you say "Transplant Tissue Rejection"?

[Doug M.]

Re: C2 Stalling

Pat, Just a small point, but maybe the fuel screen on the end of the pickup is partially plugged.

Doug

[Duke W.]

Re: C2 Stalling

That would restrict fuel flow and cause the engine to cut out at WOT high revs, but is not a likely cause of stalling at idle.

Duke

[Gerard F.]

Re: C2 Stalling

Joe,

You've heard this theory before.

Maybe it is Pat's gas cap not venting air out. You do a hot run, the mufflers heat up the fuel line and gas tank. The gas tank builds up pressure due to a faulty gas cap, that puts extra pressure to the fuel bowls. You stop at a light and idle, and you get that drip drip drip into the air horn and then flood out.

I put my original restored gas cap on my 67 last week as I'm getting ready for judging later this month. Took a half hour run up the hill in about 100 degree heat. It ran a little hotter than usual, and when I got back to the garage and shut down, it wouldn't restart quickly as it usually does. Pulled the air cleaner and there was that drip, drip drip. Funny, it doesn't do that with my aftermarket vented locking cap.

Didn't think to pull the gas cap, but I'm going to try the same run this weekend, both with the old cap and the aftermarket one, check the gas tank pressure, and see if it makes any difference.

Maybe its one of those simple things, Pat.

[Patrick M.]

Re: C2 Stalling

First, thanks to everyone for their assistance on this problem.

The camshaft is part# 3849346, lift at the valves is .485" and verified by dial indicator. I believe this is correct for the SHP. The Holley is a 4150 - 2818.

In '06 after Duke straightened me out on timing the car performed well with no overheating, excellent throttle response and no stalling. The idle was not " nickel standing " smooth but, in my opinion, right with the valve train.

Duke, the heat riser is free when cold. I will wire it open for my next test. I feel reasonably certain the stalling, ocurring only after complete warm-up ( ambient 90+ ), is fuel system connected. Adding Sea Foam to the gas and replacing the contents of the tank there has been some improvement.

I'll check the gas cap and add another shot of carb cleaner but I'm beginning to think that I may have to remove and clean the carburetor. Not a very pleasant thought.

Again, thanks to all of you for your input. The only thing that I would add is the patient prefers that the doctor address him.

Pat McInerney

[Patrick M.]

Re: C2 Stalling

Sorry all, I meant to include comment on idle vacuum.

The reading was taken on my Sears Vacuum guage which is nearly as old as the Corvette. It was relative only to the reading taken before I adjusted the idle screws. I think a new guage is called for.

Valve lash was set at .025" hot.

Pat