Car Slightly Jerky when Cruising

[Red66GT]

Hey guys,
My car feels slightly jerky while cruising, kinda like a manual tranny car feels if you're cruising w/ real low RPM's, which I'm not doing.

The car feels fine when accelerating and also when decelerating, it's just jerky at a steady cruise for some reason. Mildly jerky, not severe, but enough to post about.

I have a 4 spd manual tranny, the 289 w/ Edelbrock Performer RPM heads, a mild cam, long tube headers, and a 600cfm Holley carb (vacuum secondaries) and the car has ran fine before, no jerkiness.

Now, do you guys think its a carb problem, an ignition problem, something else? Basically, what should I check for first?

 

[Red66GT]

Oh yeah, as far as ignition goes, I have the Pertronix electric ignition, so it's definately not a problem w/ points in case anyone may have thought that was the problem.

 

[latamud]

Maybe a bad motor mount. Try hitting the throttle while watching the engine, does the engine jump? If so the motor mount is bad. Or, maybe you have something going on in the leaf springs?

 

[Red66GT]

I'll look into the bad mount, anyone w/ any other possible suggestions as to what it may be?

 

[1970 slantroof]

Could be you are running a little lean on the mixture at light throttle. I have had this problem at times on other cars. You could try one step up on the jets or raise the fuel level slightly to see if it goes away.
Howard

 

[D.Hearne]

is it steady, or just occasional? plug wires grounding? I also agree it could be with the carb too. Bad fuel or lean like 1970 slantroof said