[rtyauch301]

ok so iv replaced my plugs points plug wires dist cap readjusted the carb fuel pump is only about 2 months old and when i give the car wot it runs smooth for like a second or too then i start loosing power and the engine tone completely changes if i let off the throttle and come right back some times it clears up and goes fine then others it clears for a few seconds and back again same thing . im running outta ideas here. its a 1970 pontiac 400 2bbl #16 heads all never rebuilt 128k miles if that maters

[cobalt327]

Is the choke completely open and not being pulled towards closed when you floor it?

Float level in the carb, plugged fuel filter(s)- (there is one in the carb's fuel inlet that can be overlooked), mechanical advance sticking or not working correctly, weak or broken valve train parts- especially springs, restricted exhaust system are a couple things to check.

What is the initial timing and total timing set at? That engine has 10:1 CR, so the timing may be excessively retarded to prevent detonation.

When and how did this start- all of a sudden, gradually, right after a repair or modification? After racing/running it hard?

[rtyauch301]

just all the sudden was driving home from work gave it some gas to get on the highway and it was doing it im gonna go look at those things right now and ill post a reply back...... also the initial timing is a 9 degree advance set it per the sticker on the core support of the car... also the vac advance is new to it was replaced about a month ago the old one had a vac leak.... also its straight piped per previous owner

[rtyauch301]

well it turned out that my dwell meter was faulty set it with a feeler gauge and it seems to be running fine now

[cobalt327]

Originally Posted by rtyauch301

well it turned out that my dwell meter was faulty set it with a feeler gauge and it seems to be running fine now

Remember, when you reset the points dwell (or gap), this also changes the timing a bit. If you're real set on a particular timing, you might want to check it.