Not being a mechanic, I hope I don't sound stupid but here goes...


I think the Harmonic ballancer on my car is acting up. Is this a part that would be replaced with an under drive pulley kit?
If so, since I would need the dealer to fix / replace it, would it be cheaper to have a shop put in an under drive pulley kit and get a few extra ponies?

 

The ls1 Harmonic balancer is basically a balancer/pully assembley all in one. Well it matters how your HB is acting but yes usually it is fixed by replacing the stock HB which is around $130 or so or you can purchase an aftermarket like SLP's for a hundred more. SLP will get you around 10 RWHP and what i like the most about SLPs is its extra-tall belt-retention walls that eliminate the belt-slippage issues endemic to other LS1 balancers . BUT remember to use a NEW balancer bolt and LOC-TITE(a must). trust me on this. i have had mine spin off before with 452 RWHP. oh yeah i wouldent take it to a dealer, if you know of a good HP shop that has a good rep. in your town it might be alot cheaper. Good luck.
P.S. you might want to post questions like this in the tech section i have seen alot of balancer questions in there

 

cool thanks, I may get the pulley kit. AT first I was told it was the crack pulley and it might cost some serious cake if the crank was bent.

If it is the HB then I'm doing a pulley kit.

 

how do you replace a HB without removing or raising your engine? My '95 has this big black crossmember frame that is 6 inches or so from the lower accesories. I am just curious, sorry to butt in on your thread....

 

 

I lost a motor by not knowing about this advice a few months ago. I posted about in tech in early October but can't find it as it is over two weeks old and apparently the search function only goes back two weeks.
Short story is due some research before removing the harmonic balancer. Mine came off after some engine work despite following the tech manaul procedure to put it back on. In coming off I believe it bent the crank and wiped a bearing because after we put another new one, the motor lasted all of about four minutes.

 

I had mine come off on the highway. Talk about a good way to scare the $&@#$!#@ out of someone!

 

Couple of things. There's a lot of work involved in replacing the pulley because, essentially, everything in front of the motor has to come off or move. The steering rack is in the way so must be moved aside. This is why so many decide to also swap in a new, more aggressive cam if it's in their plans to ever do that mod so consider it now while all that stuff is out of the way. Since you're talking about an underdrive pulley, the upgrade in cam sounds like it could be a consideration for you. Otherwise, a lot of work for 10 hp.

Secondly, pin the pulley to the crank while you're in there. IMO, you must use a new pulley since it's a press fit which is essentially lost after the first install of a pulley. But you can eliminate the future possibility of the bolt backing out and the pulley walking simply by pinning the pulley when you install it. The C6 already has issues with loose pulleys so take a cue from your current problem and theirs'. Below is a pic of a pulley we pinned for a supercharger app. You can see the 1/4" pin at the 12 o'clock position of the crank snout.