Bad Dieseling... help

[80Camaro]

My bros 55 chevy has a ZZ4 engine with only about 4000 mi. It diesels so bad that you have to ease out on the clutch to kill it! He uses premium name brand gas. When you turn off the key it reverses rotation. I know it's something to do with timing but I have it set correctly. I've played around with the timing, checked out the dist. itself (brand new), and checked that the balancer hasn't slipped. All check out. It has backfired through the carb a couple of times. Any suggestions?

[Fast01]

If the dieseling you refer to is when you try to turn off the car it may be the alternator. I don't know how you have the car wired, but sometimes voltage will creep back to the ignition from the spinning alternator even after the key is turned off. You can fix this by wiring a diode into the alternator circuit. Basically a diode will only allow current to flow in one direction and prevent voltage from creeping back to the ignition. For the life of me I can't remember the rating of the diode neede or exactly where to splice it in. Maybe someone else here can help with that.

Oh, and another thing. Plugs could be too hot or the throttle blades may be open beyond the transition slots exposing the main circuit and fueling the car. The combo of the two will continue to ignite the mixture without any power at all. Either way, I doubt it's a timing problem. You have an ignition source somewhere that you have to find. Another possibility is heavy carbon buildup, but you shouldn't have that problem with only 4000 miles.

[gordonquixote]

Is your idle set too high?

You may also be getting electrical fedback from the alternator as mentioned above - you can buy an islolator (diode) from Jegs/Summit this should stop stop dieseling if it is an electrical issue.

[MonzaRacer]

Give it a shot with alt unplugged if that doesnt work try this.
first check you centrifical advance and I use stock weights with lightest sprring I can get it to return to rest posistion with.
Then set it at about 14 to 16 egrees of initial timing and idle it down and adjust the mixture too the highest manifoold vacuum possible with smooth idle.
Now hook vacuum advance up to manifold vacuum, and readjust the idle speed as low as it can in drive.
yuo can also readjust or finetune the mixture with vac advance hooked up too.
If you run out of idle speed screw you may have a bad vacuum leak or the secondaries may be open too far and you will need to remove car(if holley) and flip it over and close the secondaries some more.
also you may need to drop the powervalve size too.
This setup will let it idle much better, get better mileage and let the butterflys to be closed as much as possible.
On the outside chance you have too large a cam and can close the blades enough to get idle mixture to affect running then you may need to drill a small hole(I start with 1/32") in the primary throttle blades, towards the front, centered between the shaft, outer edge and side to side.You can also keep upping this till you can get it back into the idle circuit effectivly but dont go over 3/32, if it need s to be bigger then you may need to open the secondaries more as long as its not a 4 hole idle setup carb(ie 4 idle mixture screws.
Good Luck and if you need any more help pm or email me at [email protected].
Lee Abel
AFTERMARKET PERFORMANCE