Help - engine is 'dieseling'

[coolblue65]

So I got my car up and running again (its been about 6 months), during my initial short around the block test drives everything seemed fine. However after a l5 min session with some hard driving when i turn the motor off it kind of pops and chugs for a few seconds then stops (I was told this was called dieseling). This is a new problem, and I don't know what causes this condition and I don't know how to fix the problem.

I would think it has something to do with the new Trick Flow heads I put on because it is the only change to the car, but I dont know how, the car has slightly less compression now also.

Someone PLEASE help

 

[6Stang7]

How hot did your engine get? What is the timing set to?

-Shaun

 

[D.Hearne]

Your carb's throttle plates are open too far, allowing too much fuel/air mixture in after you shut the motor down. Readjust the idle setting and if it doesn't want to idle, open up the mixture screws to compensate for the reduction in the throttle setting adjustment

 

[Ozsum67]

Back the timing down a bit, slow down the idle rpm on the carb setting, or turn it off while still in gear if it is an automatic.

 

[coolblue65]

Thanks for the quick replys.

Dhearne & Ozsum67 - I did seem like it was idling a bit to high, and my car already runs plenty rich, so I am thinking that adjusting the carb is the solution.

6stang7- The engine got up to maybe 200 degrees- the car runs pretty cool.

Ozsum67 & 6stang7 - My timing is set at 12*, I never thought that was too high. I will try the carb adjustments first, and if that doesnt work will try backing down the timing.

Also someone else suggested higher octane gas, right now I run regular, would it help to run premium?

 

[splinterddt]

With my big block I notice it will diesal on regular gas. I run premium just to get rid of this. I have not noticed any other benafits of premium gas. Down side is cost. I also add octane boost in the summer when I go drag racing. Like previouly mentioned, make sure to check carb adjustments and timing. Those are usually the most common cause of diesalling.

 

[Hack]

If it's the gasoline, you might notice some pinging on a hot day as well. To me that would be a sign to immediately up the octane. Hopefully the carburetor and timing adjustments can do it, because premium can get spendy. That said, I've found I have to run premium in my 250 when it's mid 80s and above. Otherwise, I've noticed a little detonation going up hills, etc.