big ben

i have what is said to be a 85 roller bottom end stock heads stock cam performer rpm intake 670 street avenger (new last year) mechanical fuel pump 4 hole carb spacer shorty headers and dual flows unerdrive pulleys and electric fan stock ford brain box ignition it runs pritty good starts fine w/no choke (manual) and what happens is when im gettin on it it will start spitting and popin at about 5500-6000rpm and it wont do a dounut and i know how to do one but when i jump on it and turn it will do anice 180but then cut right out dead until i grab some clutch then it comes back fine any help wold be great thanks

lxman1

Sounds like perhaps your valve springs are shot and the valves are floating above 5500rpm.
That engine will be fastest if shifted @ about 5000 to 5200rpm, since the stock cam and heads run out about there.
Also sounds like you have some float level issues which could be the cause of the cutting out if they are too low.

big ben

i never even thought of that is there a way to test springg without taking them all apart

lxman1

Not that I know of.
I would check the float levels first. They should be just below the sight hole in the bowls when idling.

big ben

float levals are fine and it will do a fine dounut in loose or wet conditions when i rev past 5500 it sounds like the lywheel gear is hitting somthing its a very strange sound ive never herd before