I have a zz502 crate engine with a 750 speed demon carb. My timing is set at 10 degrees. When I shut the engine off, it sputters for a few seconds afterwards. If I bring the timing down more, it runs like crud and still sputters. Any ideas? I've also been told it could be the octane of the gas, which I've never heard. I'm running 91 octane at sea level. I was also wondering if it could be the distrubutor 180 degrees off. Would it even run that way? I would also like to find someone with the same combination to find out what jet sizes their running? I would appreciate any inputs, it's annoying me and I'm sure it's not good on the engine.

Idle speed too high?

By the distributor 180 out, I meant pulling the distributor out and rotating the crank.

The basic problem is that your throttle is too far open. Instead of retarding the timing, advance it by using the vacuum advance connected to the manifold vacuum. This will bring your idle speed up, then you can close off the throttle to reduce the idle speed and eliminate the run-on.

That should work!!

How do I advance it with the vacuum advance, not sure what you're talking about. Please explain.

I had this problem really bad before. then i changed out the distributor cap and rotor, and then everything was fine. Good luck.

Where is your vaccume advance hooked up to?
Is it hooked to a small nipple on the carb?
Is this fitting above the throttle blades?
(in the middle section of the carb) If so, that would be Ported vaccume!
You need full manifold vaccume, which will increase your timing at idle. There should be a nipple on the base of the carb, or there might also be one on the manifold itself. That way, you can turn down the idle circuit on the carb. You'll end up with a smoother idle, and no run-on.
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Originally posted by n2deep:
By the distributor 180 out, I meant pulling the distributor out and rotating the crank. It WON'T run with the distributor 180 degrees out!

Originally posted by MalibuJerry350:
</font><blockquote>quote:</font><hr />Originally posted by n2deep:
By the distributor 180 out, I meant pulling the distributor out and rotating the crank. It WON'T run with the distributor 180 degrees out! </font>[/QUOTE]Actually it will, but it will run just horribly, snorting and spitting. I've done it.

You could try 12-14º advance, too. My driver, with a near stock 350, likes 14º initial plus full vacuum on top of that for 24º at idle.

If timing and idle speed is correct do not overlook the possibility that the return spring is too weak. Sometimes we overlook the simple and obvious.