Bought an 85 Z28 bout a week ago...ran well but started dieseling. We attempted to do the timing but ever since we moved the timing it feels like its missing...but ONLY at low rpms. I replaced the cap and rotor with a MSD one and replaced the plugs...any ideas?

 

What procedure did you use to adjust the spark timing? There are many reasons for dieseling besides spark timing.

 

Hmmmm....dieseling. You didn't put a train horn on your car too did you?
But seriously folks, a little more info may help. Do you still have FI or has it been converted to carb, stock cooling fan setup, etc.

 

Carb 305, auto, everything is stock except the cap and rotor. And i used a timing light.

 

Oh and i forgot to say that the misfire didnt start happening until we started changing the timing. And since we adjusted the timing when you get on the throttle its almost like the carb is flooding...and i cant find any carb adjustment screws...

 

What kind of carb? And where did you set the timing at.

 

Thats the thing...i dont know exactly which carb. I know it has a Rochester Quardrajet on it...but i cant find the model on it. And we set the timing at 5 btdc but then had to change it cuz it ran like crap and we advanced it by ear so not sure. Chiltons says it is supposed to be set at 6 btdc so i tried to set it at that but it didnt seem to run even close to right so had to do it by ear again.

 

Look under the hood and see if you have a tune up procedure label. If your engine has the electronic spark timing (EST), you need to disconnect it before setting the timing. Look for a long plug with a tan wire/black stripe that comes out of the fat wiring harness, and is located on the passenger side between the firewall and strut tower. Disconnect the plug, set the timing, then reconnect it.