sbc dieseling

[masterblazer]

so i put a 350 together with a stock crank, rods, pistons. put on a new dampener, new lunati cam, new alum intake, 2.02/1.60 heads.and a used 750 double pump holley. and used the old distributor. put it all together and it is deiseling like crazy so i thought it may be the stock dist so we welded it solid and tried it again and it is still doing the same thing just not quit as bad. we took the exhaust off and just left open headers to try and cool down the cylinder temps but still no luck. we set the timing anywere from 15 degrees all the way to 30 degrees locked out just trying stuff and no luck. what should i try next?????? thanks

 

[BoondocK5]

Dieseling is usually only caused by one or two things. Timing being all jacked up, or temperature being all jacked up. Make sure your timing is pretty close to correct, then get an "honest to God" temperature reading.

 

[masterblazer]

we put a 180 degree thermostat in it and brand new guages and it never showed the water temp getting above 185 to 190. i am still somewhat new to putting engines together however i have mechanical ability. its just been driving me insane. would it help if i tried a different stock advance distributor prolly??

 

[BoondocK5]

First verify your timing is correct, using a timing light.

 

[Stomis]

Make sure your setting base with the vacuum line plugged/crimped!

Should be 12-16* depending on what your motor likes. If its not getting hot than there really isnt much else it could be.

 

[diesel4me]

dieseling

All it takes is a red hot peice of carbon,an exhaust valve,or spark plug electrode to light off the air/fuel mix after the ignition is switched off..usually though,you'll hear a pinging while accelerating under a load if thats the case.just as you would if the timing is over advanced..

The idle speed also increases the tendency to diesel,the higher it idles the more likely it'll be to "run on"..
I would return the advance weights to normal in the distributor,a retarted spark can also cause dieseling by increasing exhaust valve and combustion chamber temparatures..

If your using a stock harmonic balancer,dont forget they can "slip" on the rubber and give false readings with a timing light..

A "long shot" is some GM vehicles had a voltage feedback problem in certain years,that let the ignition coil get voltage with the ignition off until the electric fan ot heater blower motor stopped turning completely..a diode had to be spliced in to the power wire in the item that caused it (unplug it to check )...