vibration after opti-spark install

[tob3soon]

I just installed a new optispark and cap rotor in my 95 z-28. The vehicle was surging and that's why I replaced the opti-spark. Now after the new opti-spark the surge is gone but the car has a vibration around 2000-2500 rpm's. I checked the balancer and it looks fine. what else could cause this??

[Blue Bowtie]

Make sure the balancer is oriented correctly. The balancer outer ring (inertial damper) is often drilled at the factory for final crankshaft balance. You can bolt the balancer on in almost any position, but only ONE is correct. There is an arrowhead cast into the balancer ring near the hub mount, and it should align with the keyway in the crank snout. If you look closely, you can see that I painted the one on my '94 so I couldn't screw it up:



There is no keyway in the balancer hub, so there is no "foolproof" way to just slap it on when you install it. You must align the arrow with the crank throw on the #1 cylinder. An easy method is to use a piston stop, locate TDC on #1, then install the balancer so the arrowhead cast into the damper is at the 1:30 position - Or pointing straight at the #1 cylinder. Rumor is that SOME engines have the arrow at the 12:00 position in this crank position, or retarded 45° from TDC on #1:

http://www.gmhightechperformance.com.../photo_13.html

Mine is smooth as glass at the TDC position.

[cuda_dude]

He wouldnt have needed to remove the hub to change the opti

[tob3soon]

Thanks. I did not align the arrow to the keyway and I bet that's whats throwing it off. I'll try that tonight when I get home. thanks again for the info

[Blue Bowtie]

He wouldnt have needed to remove the hub to change the opti

True, but the damper ring is in the way, and there are three possible ways to bolt it on.