I built and installed a new 383 stroker motor in my chevelle and it vibrates at idle and smoothes out at higher rpms. The stroker kit was balanced from harmonic balancer to the flywheel including the rods and pistons.
I have a 72 Chevelle with a TH350 trans, CompCams 268XE, DUI ignition, JetPerf Quadrajet 750. Everything runs great except for the vibration.

Timing retarded? Idle mix?

Does the 268XE have a lope at idle?

Loose crank pully?

Is it a vibration from a miss?

Sorry, just tring to narrow things down and eliminate as many small things as possible. off hand I would say if it's not just the lope in the cam it may be idle mix on the carb.



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Tommy B.
71-72 Malibu (http://www.geocities.com/beldarr/Chevelle.htm)
"I'm high all right, but on the real stuff
High octane gasoline
A clean windshield
And a shoe shine"

I'm with Beldarr on this one. I'd look for a weak cylinder. If you can find a shop that still has an oscilloscope, you could have them do a quick cylinder balance test.

Make sure your idle mixture screws are balanced and set properly (highest vacuum reading).

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...Dennis
The '69 (http://chevelles.com/showroom/fine69_03.jpg) & the '96 (http://chevelles.com/showroom/fine69_02.jpg)
Team Camaro (http://www.camaros.net)
Camaros Limited (http://www.camaroslimited.com)

I'm having the same problem now. Just did a tune up consisting of plugs, wires, carb rebuild, and valve lash adjustment. Engine runs strong, very responsive, but idle fluctuates and engine jumps slightly randomly at idle. I tried tuning it out by raising the idle but it doesn't tune out until the mechanical advance comes in around 1000-1100 rpm.