I have a 383 stroker engine in my ElCoolmino, getting run on and backfire …

[57NAPCO]

Just started doing this a few months back, I don’t drive it much. But I now have to turn it off in gear (auto) so it wont run on (warm)

Also if I’m off the gas decelerating for a bit it will pop back thru carb after initially after giving it gas….runs great other than that.

Thoughts from those who know more than me…

Timing ?

[Shifty One]

Timing would be my first guess....

[57NAPCO]

Advance or retard ?

[Shifty One]

My initial thought that it was too far retarded, but I've experienced run-on far more with too far advanced. How's it start (cold)?

Also, have you confirmed that the distributor isn't 180-degrees out?

[57NAPCO]

Starts good cold with a few pumps. Giving to much gas while cold will also cause backfire thru carb.

[geezer#99]

Backfire is from being lean and retarded.

[57NAPCO]

Thanks,
… to much going on, i have to wait a bit before getting into it

[Dead Parrot]

Usual suspect for after run is too much idle. Often due to vacuum leak or bad timing.

Make sure the distributor hold down bolt/nut hasn't backed off. If that gets loose, timing can change.

[Myself]

First suspect on a vehicle that's been sitting OR doesn't get driven much would be sticking advance mechanism in the distributor. Easy fix.

[57NAPCO]

Thanks

[mattfranklin]

What the other guys said about timing. A little more timing will bring your idle speed up, so you can back off on the idle speed screws, closing the throttle.


Also try premium.
It resists knock and preignition.

As a last resort you can install an idle speed solenoid. It bumps up the throttle position when the key is on for a stronger idle, and it closes the throttle a bit when the key is off, giving less of a chance to run on or "diesel."

[mattfranklin]

Also, if you have combustion chamber deposits that can build up over time, you can clean them up with a bottle of Techron Concentrate (sold by my employer) used at the right dosage. One bottle ounce per gallon of tank, 20oz for a 20gal tank. Drive normally. Stop and go driving is fine. You don't need to blast it out with WOT runs.

[67 Burb]

Originally Posted by 57NAPCO

Just started doing this a few months back, I don’t drive it much. But I now have to turn it off in gear (auto) so it wont run on (warm)

Also if I’m off the gas decelerating for a bit it will pop back thru carb after initially after giving it gas….runs great other than that.

Thoughts from those who know more than me…

Timing ?

My theory is, don't mess with your timing if you're getting run-on after turning the ignition off.
Once you turn off the key, your distributor is not producing spark, so playing with the timing does nothing.
Usually too high an idle is what causes run-on.

[57NAPCO]

Thanks again y’all, the Coolmino has been sitting in the shop waiting on me to get off my arse and work on it. I really need to pull the engine and fix/check some leaks out, find some quality headers, put an electric fan on and finally work on the interior since I bought a donor SS 73 to pull from.

[raggedjim]

I like it! Rg