Engine Knocking and Dieseling

[PurpleX]

Hey all, having a problem with the engine running on and dieseling quite bad when the ignition is shut off. The car runs rich to begin with, idles fine at 800rpm. Aside from rebuilding and checking the adjustment on the carbs Im looking for some suggestions. Its a 1969 Hemi, all stock, dual Carters, timing is at TDC on 91 octane fuel which is the best available here. Need better gas maybe?
Thanks.

 

[mattsmopars]

I am running my stock 69 hemi engine at 16 degree initial timing and 34-35 total timing. I know the manual say 0 degree or TDC but that was with 100 octane leaded gas. If you raise your initial timing up you will most likely have to limit your total by limiting the travel inside the mechanical advance in the distributor. Might be something to check out. You may also want to do a compression check to see what your cylinder pressures are. Some cause a small cam lets the engine make a lot of cylinder pressure that can cause pre-ignition.
Matt

 

[Pops1967GTX]

The Gas..... the Gas....... the Gas..........

 

[poly3521]

The knock and dieseling sounds like timing to me. As far as being rich, might want to check that the throttle linkage is adjusted right. Might be running off of both carbs when it shouldn't be. Or the primary carb needs re-jetted/different metering rods. Just my 2 cents.

 

[benno440]

more timing, after that check to see your throttle blades are not too far open, i had problem with run on, took me ages to find it but i found the throttle blades were exposing the slots in the carb too much and causing my run on

 

[superbeedave]

Your throttle plates are most likely to far open due to your base timing is too low. Dieseling is from throttle plates being to far open at idle or too high of idle. Just my 2 cents!!

 

[PurpleX]

Hmmm...ok, so advance the timing to say 10 BTDC and how do you adjust the throttle plates?

 

[bm02tj]

Your idle speed will go up with the timing advance so you will turn it back down by closing throttle plates with idle screw

 

[Photon440]

What part of Canada are you in? I never have problems finding 94 octane.

Is your car auto or four speed? If it's auto, try shutting it off in drive to reduce dieseling.

 

[PurpleX]

What part of Canada are you in? I never have problems finding 94 octane.

Is your car auto or four speed? If it's auto, try shutting it off in drive to reduce dieseling.

Im in Halifax, never seen anything other than 91 octane. Its a 4 speed car as well.

 

[PurpleX]

Well, I have the idle mixture screws adjusted as well as the throttle plates. Runs better now. I have the timing set at 8 BTDC, more than that and it knocks bad under load, less than that and it runs on when shut off still. Have to try some better fuel than the 91 octane that's the best available here. Thanks.