motorvation2go

Powerbond is a great choice. High quality and reasonably priced. I installed 25% UD unit last year. No charging or cooling issues whatsoever. Incidentally, only my main belt (alternator, water pump, etc.) is UD. A/C is stock length.
I used Goodyear Gatorbacks. Main (long) belt #4060775. A/C belt#4040420.
No more chirping, squeaking/squaking sounds!
Best of luck. I'm confident that you'll be happy with this setup.

2079

Great info ,thank you all.

Bill Curlee

I have the 25% UD pulley. ZERO charging problems on a heavily modded engine with lots of lope!

BC

The Wrench

If for no other reason, installing an aftermarket damper has to be good for the adjacent parts (belts, accessories, seal, oil pump) since the GM units invariably wobble like an arthritic wino. My ASP is super smooth, and the stocker on my new Caddy wobbles at least 1/8 inch, sending the belt tensioner into a frenzy. I'm going to try to get GM to replace it (wish me luck).

DG

Z06FRC

So is 25% UD good for my stock bottom end or should I go with a 10% UD just to play it safe?

lucky131969

Perhaps I'm misunderstanding, but I do not know what the correlation is between a stock bottom end, and the % underdrive used......

Z06FRC

The point if the UD is to reduce torsional vibration in the crankshaft, right? I just want make sure that I'm not upsetting the balance of the crankshaft by going with a lighter pully.

lucky131969

No. The amount of underdrive reduces the speed of driven accessories...reducing drag on the crank..... and is supposed to provide an increase in horsepower.

dankhts

My stock damper was squeeking and comming apart, so when I did my mods last summer, I installed a Power Bond 25% UD damper... no charging or cooling issues, couple dozen laps at the strip, a 3,000 mile road trip etc....only have about 4,000 miles on it total so far....

Z06FRC

Ok that makes perfect sense, thanks. Guess I'll be ordering the Powerbond 25% UD.

ILM-Express

more good info

Pro Street

I used the Summit 25%UD when I did my cam swap 2 years ago and no problems.

LoneStarFRC

25% Powerbond - pinned crank - Goodyear # 4060775 Gator-Back belt.
No charging issues. Happy camper.

Y2Kvert4me

Kinda, and no.

You were already given the reason for the underdrive ratio (to slow down the speed of the driven accessories)...But you actually did touch on a good point about the weight.

The Powerbond is not lighter than the stock balancer....If I recall, it weighs a touch more. For a balancer, this is a good thing, as it's primary function is to dampen engine harmonics. Driving the accessories is the secondary function.

A lighter balancer reduces it's ability to dampen, and the ASP is a good example of this, as it is aluminum and lighter than stock, and there are quite an alarming number of people that have broken timing chains with the ASP balancer.
Some may say there's no proof or direct correlation between the two components, or cause of failure, but personally, it almost seems a sure bet the next person to post a chain failure will likely be running a lighter balancer too... It's just gone beyond coincidence IMO.

Of course I could be 100% wrong, just something to think about.

As for the 25% underdrive ratio - no problems with charging, coolant temps, or power steering. But also consider most people installing one are also doing it with a cam, and that usually means increased idle speeds, which will kind of cancel it out in idling conditions, the one and only engine speed where underdriving could be a factor in accessory performance.

clif

Interesting Information. The Innovator's West balancer that I post a picture of, is actually a 10% OVERDRIVE pulley! I had to place a larger pulley on my ProCharger unit to keep from building too much boost. I do not have ANY charging issues.

2079

Since it appears that there are no issues regarding charging etc. whit an under drive pulley aswell being good insurance before the original fail,I'll be ordering one of the POWERBOND unit.
Still undecided ...do I go whit the 10% or the 20% why one over the other?
Do they really provide more HP,If not I probably will stick whit there standard size replacement .
Also whit all 3 model I do retain the same AC belt correct,
and any special bolts required for the install.
Thank you for helping in my selection.

lucky131969

Just curious. Why would you install an overdrive balancer if you were concerned with making too much boost ?....kinda defeats the purpose.

2079

lionelhutz

The 10% will be fine and the 25% should be too. Still, I'm finding it hard to believe the battery voltage isn't dropping more at idle with a 25%.

If the car doesn't idle much then it doesn't matter. If it idles a fair bit then it could and it could really matter if you live in a really hot climate where the high speed fans run a lot and the car is iding a lot. Like driving in a lot of stop and go traffic in Arizona for example. An auto that idles will be worse since the idle speed is lower compared to a standard.

Peter

corvettecrazy2