running rough only at part throttle?

Hey Guys,

I just picked up a little 62 nova, owner didn't know much about it. I through in a new fuel pump, water pump and some misc, and the little SOB runs and drives like a champ!

Well sort of, i hadn't noticed till i took it on a drive that it's stumbing really bad at part throttle. At first i thought it was a tire out of balance but soon relized it was the motor.

Even in park it does it? Idles fine, pulls fine, but if you runnin it about 2000-2500 it just shimmiys and shakes like crazy? Checked for vacum leaks and/or any other notible issues? Any thought?

It's a straight 6 250ci with a single?

 

Hi Primed55,

When you open the throttle at 2250 rpm it pulls fairly hard and runs smooth? In every gear?

 

yeah,

 

is it advancing the distributor?

 

i was going to suggest this too----both centrifugal and vacuum.

 

Might try running it with the vacuum advance disconnected to narrow things down, with the vacuum line plugged of course.

 

Already tryed that... I put i new fuel filter on it before i got it running and am already noticing some crud, thinking maybe something got sucked in?

 

!!! Just went to double check something and relealized i had unpluged the kickdown not the advance... Blocking it off did fix the problem! !!!!

 

Sounds like the dist. shaft has excessive wear or the point plate it's self is jumping around under high vacuum advance conditions. either can vary the point gap enough to cause a miss/rough running.

 

Check the points lead too, bad insulation or loose connection.