[jimib]

Hi All,

My engine almost stalls and sometimes does stall out at red lights and stop signs after it’s completely warmed up; running temp around 190.
This rebuilt 400 has about 800 miles on it (auto transmission).

Timing: I’m not sure what the timing should be, but I have it set at about 8 to 10 before TDC. This is where it seems to run best. I have to guess because the timing numbers only go up to 6. The timing chain and gear (double rollers) is new as with the rebuild

Idle: about 600 RPM.

Dwell: about 30 degrees. (has the stock points and they are relatively new)

Carburetor: Holly and rebuilt with engine rebuild.

I’ve heard of the term “Vapor Lock” but I’m not that familiar with the symptoms of such. From what I understand thus far is that this condition obstructs fuel delivery to the carb.
Could this possible be the problem?
This set up has the fuel return line. There is a steel portion of gas line that runs up right against the block. I’m not sure yet how I would go about re-routing if need be.

Any ideas of what I should do?

[red76TA]

see how hot the line gets when it stalls, if its a too hot then re rout with a rubber line or something

[BVR421]

increase curb idle by 100rpm

[Ron H]

Look down carb when engine is running and try to see if gas is dripping from the nozzles. Check float height. Does it do the same thing when turning sharply? Fuel pressure can also cause this.

[bobd1959]

Does not sound like vapor lock since that would happen even when driving. Is your idle of 600 rpm in drive or netural? You should raise your idle a bit, at least 100 RPM in drive.

[jimib]

It's 600 RPM while in neutral. I'll raise the idle and see what happens.

Ron: I'll look down the card and look for gas drips. However, making a sharp turn does not affect the engine. You also mention fuel pressure. Possible a failing fuel pump? Should I replace it with a quality aftermarket pump rather than the stock fuel pump?

Red76: The fuel is certainly too hot to touch. Perhaps re-routing with rubber may help.

[RicksGTO]

I agree, 600 rpm with an automatic is below what most engines will handle well in gear, even if everything is tuned perfectly, 650-700 in gear is a good minimum to me for an automatic. On my GTO with a rebuilt Holley, I had to set the 2 idle mixture screws carefully with a vacuum gauge hooked up till I got them right at the maximum vacuum level. Start at about 3 full turns out with the gauge attached and go in 1/4 turn at a time on each and see what is best, that can make a big difference in idle quality sometimes. Timing is critical too so you might try some timing tape on the balancer to be sure where your really at, 12 degrees initial at 750 rpm in park, with the vacuum advance disconnected is a good place to start probably. Also after timing is set, try hooking up your vacuum advance to either manifold or ported sources and adjust idle back down accordingly, to see which the motor likes better at idle. Lots of people will say one is better than the other, but every motor is different. Like said above, make sure your float level is right at the bottom of the site plug threads too. My return line runs inside the frame horn near the engine, but it's a '69 GTO, so your original routing may be different.

[72LemansFreak]

I concur with Rick make sure your mixture produces the highest vacuum at idle, then set your idle.

As food for thought, the factory specifications for my car (350 2 bbl) call for 625 RPM in drive. With the holley 4160 on it now, I have it at about 675 in drive.

Another thing to consider are vacuum leaks. And easy way to check for this is to get a spray bottle with water and spray around the intake manifold flanges, carb mounting flange, and any other vacuum fittings. If you notice the RPMs coming up when you mist with water, you've got a leak.

When it doubt locate the factory tuning (dwell, timing, etc) specs for your year and size of motor. It's a good place to start.

Good luck and keep us posted.

[Region Warrior]

Does it surge?

Raise idle and check for vacuum leaks as earlier post's suggest.

Vapor lock occurs after engine is shut off when hot.

[68MeanVerdoroGreen]

Don't stop at red lights or stop signs!

[jimib]

I wasn’t aware of timing tape. Looks like a great product now that I’ve researched it. I can’t tell though if it goes around the harmonic balancer or somehow sticks to the timing chain cover.

A lot of great suggestions.

[Brian D'Amico]

As said before.. Check for vacuume leaks

[SGTGTO]

Ditto on the vacuum leaks. Had the same problem once... twisted pushrod, broken intake spring, sideways rocker. Lifter collapsed...

Same problem as your describing.

[sts]

Older folks may recall the Cheech and Chong albums. Trying to start a dead car, Chong suggest that they check the air in the tires as part of the troublehshooting process.

Anyway, here's something you might wan to do before even upping the idle: Check the tranny fluid. Not always, but low or high tranny fluid level can affect the idle and also make vehicles stall.