I have a 400 built up to a 408 with some high performance parts from tim meyer. it doesn't run correct however its not bad. it used to run a lot better when i just rebuilt the motor last summer. its seems to run hot once warmed up, however the temp has never gone over 200. once its warmed up, it will "pop" when taking off (manual trans), and hessitates when you step hard on the throttle. It also pops through the exhaust when you coast in gear. it doen't want to run as well when its warmed up. its not terrible, but it lacks power. the fuel milage also sucks lately. also, it "diesels" (turns over for a long time after its shut off) when you shut it off. do you think this is timing or carb issues? i have it set at top dead center. does it need to be retared or advanced in your opinion? I have a procomp (i know they're crap) ignition on it now, however the brand of ignition is not the problem i don't think. The carb is a 670 CFM Holley truck avenger and i did set the jets down a couple sizes. I need to get this truck running right, as it is my only vehicle right now, and it gets about 3 MPG (used to get 10-13) and doesn't run RIGHT.

Thanks,
TheBlueMule

 

Sounds like too much advance, does it turn over slower than it used too? Are you saying that you have the timing set at TDC meaning 0 degrees? Normally 4-8 BTDC is about right, which if you have it set at 0 than the too much advance theory is out the window and I would check the carb, if the needle and seats aren't closing this might cause the dieseling, and if it is not providing enough fuel under acceleration this could cause the back fire, also if it is running lean enough this could also raise operating temps and chamber temperature enough to cause dieseling too.
-Johnboy