Stuttering above 6 grand v45

[moparman47]

recently i upgraded my exhaust from stock to a 4 into one mac header with a supertrapp (cause orig system developed nasty rattle) because of this i rejetted carbs with a dyno jet kit. stock jets were 98 and it was running lean, closest jet up was a 120 now its better but running a little rich but cant get away from stutter at about 6 grand. pilot screws were adjusted and im waitingh on a k&n filter as well any ideas about the stsutter will provide any other info if needed thanks for any help Estus

[agraebner]

That seems like quite a size jump in mains. What kind of kit did you install(which stage)? Did it have new needles? did you change the idle jets or mixture screw??? Where the carbs SPOTLESS inside when assembled? Is your fuel filter restricted? Is you fuel pump providing sufficient volume and pressure?? The air filter will make a difference whether good or bad I cant say it depends on whether your current set up is rich or lean.

[moparman47]

it was a stage one, yes it came with new needles(which we installed) carbs were cleaned at time of disassembly and kept very clean. may have to check fuel filter. pulls hard up to 6500 rpms them like i said it is almost like a missfire. i will check fuel filter next and let you know thanks so far. also just put k&n in (it just arrived) will keep youo posted on results!

[Wrider]

Like agraebner said, that's quite a jump in mains... I'd see if you couldn't jump to maybe a 102 or even possibly a 105, but a 120? Pull the plugs and I can guarantee they'll be sooty and almost fouled out.

[HYPERR]

Like agraebner said, that's quite a jump in mains... I'd see if you couldn't jump to maybe a 102 or even possibly a 105, but a 120? Pull the plugs and I can guarantee they'll be sooty and almost fouled out.

Dynojet numbers and stock jet numbers are not compatible. They use a different system.

[agraebner]

Good point hyperr, the last dyno jet kit I used was a stage 1 and 3 in the same set the smallest jets were smaller than the stock ones. So it is possible that you have installed even smaller mains than stock.....

[moparman47]

okay, i ordered a different kit i read the last one incorrectly i guess but they didnt have what i needed so i ordered from dennis kirk comes with 100&104's now should i put the 100 in the front and the 104 in the rears cause stock was 95 front and 98 rear or should i install all 104;s checked plugs rears are sooty the fronts are not thanks for all your help really appreciate it

[Wrider]

Like agraebner said, that's quite a jump in mains... I'd see if you couldn't jump to maybe a 102 or even possibly a 105, but a 120? Pull the plugs and I can guarantee they'll be sooty and almost fouled out.

Dynojet numbers and stock jet numbers are not compatible. They use a different system.

True, guess I was thinking he used stock jets for replacement.

And yes, vary the sizes, put the 100s in the front and the 104s in the rear and you should be golden.