have a 73 challenger has a 340 bored 30 over have gone threw engine and had heads done lets say the works. and at idle and low rpm it runs fine but wen i drive it runs fine till about 4000rpm its pops and spudders and has no power ......can anyone tell me what this could be thanks

 

oh timming is 2 b4 top dead center or tdc

 

J -

Do you know what your total advance is?

A few random shots:

You might not be getting enough from the dist or vac advance.

Unfortunately too lean an A/F mix or restrictive exhaust can case the same thing. What kind/size of carb do you have?

Silly question, but you don't have a rev limiter on the ignition, do you?

Archer

 

Ignition breaking up

carb way too lean

floating valve springs, caused by several things--weak, wrong install height, lifter adjustment, etc

flat cam lobe

 

no rev limiter ....and carb is a holley 750 with dual feed lines may need to clean it out cause found some dirt in the rear bowl could be why cause wen i get to 3500 i try to give it about 80% throttle to listen to see if the rear butterflies open but i hear nothing may be problem now to think of it.. and dont know what a total advance is can you tell me more????
Thanks
j-man

 

It could be as simple as a bad power valve in that Holley.

http://www.angelfire.com/fl4/pontiac...lleyInfo2.html

 

Good tech on ignition. http://www.diamondbackengines.com/te.../ignition-101/

 

I've learned that if the ignition box is slighly wired wrong, the effect of this will act as a rev limiter. I would suggest to just make sure all of your wiring is where it is supposed to be.