View Full Version : So...how hard is it to install.....

06-23-2010, 4:09am
a 25% underdrive pulley

SLP Harmonic Balancer/Underdrive Pulley - 1997-09 Corvette (LS1, LS2, LS6, LS3) [SLP100225] - $219.95$179.95 : MarylandSpeed.com- Your First Stop on the Way to Performance! (http://marylandspeed.com/slp-harmonic-balancerunderdrive-pulley-199709-corvette-ls1-ls2-ls6-ls3-slp100225-p-425.html)

06-23-2010, 10:40am
a 25% underdrive pulley

SLP Harmonic Balancer/Underdrive Pulley - 1997-09 Corvette (LS1, LS2, LS6, LS3) [SLP100225] - $219.95$179.95 : MarylandSpeed.com- Your First Stop on the Way to Performance! (http://marylandspeed.com/slp-harmonic-balancerunderdrive-pulley-199709-corvette-ls1-ls2-ls6-ls3-slp100225-p-425.html)

It is a lot of work. I didn't drop my frontend/steering as recommended by the GM manual but instead I lifted my engine since I had the intake manifold off and was swapping motor mounts.

06-23-2010, 1:30pm
Too much work for too little reward.

If you are doing a cam swap, and/or your current balancer is wobbling and needs replacing, then it would be a great time to install one.
But going through all that work just for the sake of the few hp the underdrive may free up (and no other reason) is not at all worth the effort.
At that point of disassembly, you're only about 15 small bolts away from sliding the cam out, it would be silly not to consider upgrading that as well.


06-23-2010, 1:48pm
No point in doing it unless you're gonig to be putting a cam in. Plus some say that the 25% pullies don't dampen crank harmonics enough... this is evidenced by the fact that ATI wouldn't make a 25% pulley (they only made 10%) until about 2 years ago when they caved to customer demand.

I just ordered a 10% underdrive ATI superdamper w/o AC for the track car today.... if you want to come over and watch what's involved in the install one evening you're more than welcome to.

I'm doing it b/c I have to tear down the front end of the motor to replace a leaking radiator and put in a new oil pump and timing chain. Don't want to be racing a car on a 119k stock chain and old oil pump so putting in a LS2 chain and LS4 high-volume pump.

Not doing a cam b/c I can't make any more power for the class I'm prepping the car around. Going w/ the new balancer b/c it'll slow down the accessories some and extend the PS pump's life and the ATI dampens the crank better than OEM which is good for extended high RPM use... oh and since I won't have AC I could order it w/o the AC pulley on the backside so it'll be lighter. None of this really matters to a street car.

With your car I'd get these headers knocked out and have Ed tune it and enjoy.... drive a few cammed cars and see if you like it at all. It's my understanding that you daily your car? If so you may want to avoid going into the engine.... I much prefer dailying my vert compared to my old Z06.


EDIT - my local buddy Keith Hollis (not sure if he's on here) in Hampton (moving to Norfolk this weekend) has a ASP 25% underdrive that he purhased from LG a few years back and never installed.

06-23-2010, 2:10pm
Even if it was free, I would not install an ASP. They seem to be the common ingredient in many timing chain failures.

Other than keeping the mass a little closer to center of rotation, the underdrive ratio itself has little to do with harmonic dampening ability, the other part of the problem is going to a much lighter balancer.
The aluminum construction (and small diameter) of the ASP makes it considerably lighter than the stock balancer, and it's reduced dampening ability is why it seems to be the root cause of chain failures.

The SLP/Powerbond (same identical balancers, different branding) are steel, and actually weigh slightly more than the stock balancer. These also do not underdrive the A/C, so the rear pulley remains full dia. They are a good choice, as is the ATI.


06-23-2010, 2:35pm
Good info :cheers:

06-25-2010, 4:41am
Ok, I think I will scratch that idea...

Brian, let me know when yours comes in and you are going to do it, if I have the free time, I may stop by just to soak up a little "know how info"

06-25-2010, 7:21am
Will do :cheers: