C3 Harmonic balancer rebuild?

[Tory S.]

I'm just finishing my 350 engine rebuild for my '75 and was wondering if I should use my original harmonic balancer? Do these things wear out? (If I were building a non-NCRS motor, I'd wouldn't trust a 34 year-old balancer!)

Options:
1. Clean, repaint and use old balancer
2. Have my original rebuilt somewhere
3. Get a new GM replacement balancer from Damper Doctor or other source that would pass judging with no problems


Thanks,
Tory
Original owner '75 conv.

[Joe L.]

Re: C3 Harmonic balancer rebuild?

I'm just finishing my 350 engine rebuild for my '75 and was wondering if I should use my original harmonic balancer? Do these things wear out? (If I were building a non-NCRS motor, I'd wouldn't trust a 34 year-old balancer!)

Options:
1. Clean, repaint and use old balancer
2. Have my original rebuilt somewhere
3. Get a new GM replacement balancer from Damper Doctor or other source that would pass judging with no problems


Thanks,
Tory
Original owner '75 conv.

Tory----


The main failure mode for harmonic balancers is deterioration of the elastomer (rubber) between the hub and outer ring. Many times, the elastomer will be ok even on old balancers, though. It's pretty hard to check to see if all is well, though, since the deterioration needs to be really bad before its obvious. At this point, the outer ring can be moved rotationally and/or laterally without movement of the hub.

If the engine is an L-48, a new balancer is available from GM under GM #12551537. I believe that this balancer is identical to the original, but I'm not 100% certain that it might not vary in some minor way. This balancer GM lists for about 150 bucks.

Otherwise, you could send your existing balancer to the damper repair specialists you mentioned and have it rebuilt.

[Tory S.]

Re: C3 Harmonic balancer rebuild?

Joe,
My original balancer has only 35k miles and appears to be tight, no movement/wobble by hand. But it is old.

From your post, you advise to buy new or rebuild original. So in no case should I use the original without rebuilding, right?

Thanks,
Tory

[Joe L.]

Re: C3 Harmonic balancer rebuild?

Joe,
My original balancer has only 35k miles and appears to be tight, no movement/wobble by hand. But it is old.

From your post, you advise to buy new or rebuild original. So in no case should I use the original without rebuilding, right?

Thanks,
Tory

Tory-----


Not necessarily. Based on what you described, I think your balancer may very well be ok as-is. I'd say it's up to you if you want a little extra "insurance".