Engine Engine Dieseling When Turned Off

Hinesja24

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May 8, 2016
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Have a 302 bored 30 over. 650 demand carb. The guy I bought it from had it set up for 100 octane. Once I started putting 93 in it started dieseling. Do I just need to reset the timing?
 
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Any other specs on the engine ? How handy are you with a timing light ? Borrow rent or buy one and start there . Check your timing and report back .

How was the engine setup for 100 octane ? The owner tell you that he just upped the timing or were the Pistons swapped with a piston to raise compression in the rebuild ?


Sent from my iPhone using my fingers while my auto correct makes me seem illiterate
 
Have a 302 bored 30 over. 650 demand carb. The guy I bought it from had it set up for 100 octane. Once I started putting 93 in it started dieseling. Do I just need to reset the timing?

Try backing down your idle a bit. If your idle is set too high, the engine will continue to pull in and and fuel after shut down, which can sometimes cause a "run on" effect.
 
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As mentioned... we need more information on the setup before any suggestions can be made. Sounds like a high compression, high lift cam motor...

Why would you put 93 in a motor that you were told required 100?:shrug:
 
so, let me see if I understand correctly, you shut the car off and it continues to run?

I don't really think timing would have much to contribute on it's own. regardless, you should retard the timing a bit if you're going that big of a jump in fuel. but, when I hear dieseling in gasser engines, my first thought is carbon build up on either/both the pistons and the valves. and the timing advanced timing combined with the lower octane fuel isn't helping. more like exacerbating the issue. you could try over fueling it by a little bit. the fresh fuel will help to cool off the cylinder temperature. that'll help with pre-ignition/detonation/spark knok. with the cooler cylinder temps. that should help with either reducing the run on or eliminate it. down side with a carb is that it's SUPER easy to foul out your spark plugs.

but to be honest, I would recommend going down to your local dodge/jeep/chrysler dealer, going into parts, and getting some decarbonizer. run that through your engine. it should help with the run on.