Friday, July 18, 2008

Powerbond 25% Underdrive Pulley

Another mod that gains an easy 5-10hp is the ever popular underdrive pulley.
What it does is make some of your accessories run a bit slower and they are usually lighter than stock making it easier for the engine to run. I decided to order mine from New Era back in NY. It's the "Powerbond Harmonic Balancer 25% Underdrive crank pulley" They had'm in stock for a decent price and Mike is a great guy.

From their website:

" Looking for an easy way to add some horsepower to your G8's powerplant and at the same time get better fuel economy by reducing engine stress ?? This is the best way to pick up some hp for a great price in doing so !! Powerbond's new 25% underdrive balancer for LS1's incorporates a number of high-quality features you won’t find on any other aftermarket unit. Chief among them are a pair of extra-tall belt-retention walls that eliminate the belt-slippage issues endemic to other LS engine balancers . Other unique design strengths include 100% steel construction (other brands use steel and aluminum), integral timing marks, and built-in puller-mounting threads. NOTE: Requires 1 new belt (not included). FEATURES Extra-tall belt-retention "walls"—no more thrown belts! No aftermarket tensioner required 100% steel construction Lighter than the stock balancer Integral timing marks and puller-mounting threads Keyed for high-rpm or supercharged applications Does not cause false knock retard or erratic power-curve dips ."

Once I got the pulley (after about a week) BOY was that thing heavy! I couldn't even begin to imagine how heavy the stock one must be! Now it turned out that i'd still need a new balancer bolt and a new belt since the stock one would no longer fit. I went with the following:

Belt: Gates belt # K060747
Bolt: ARP 234-2503 (or GM bolt 12557840 would also work)

For the belt i went with a goodyear gatorback belt - nice quality - from a local auto parts store.
The ARP bolt is 25-50 bucks depending on where you get it! OUCH (stock GM is 5 bucks)
No local stores had the ARP Bolt (and would charge $50 for it) so I went to and ordered it from there. The rate I'm going i'll be a frequent shopper there soon enough anyway ;)

Now the hard part was finding a place to install it! None of the 'run of the mill' places could or wanted to do it (or sometimes don't even know what G8 is) so I ended up talking to my dealership about it. They agreed after the usual "voiding of warrenty" stories blabla. Great I thought. I made the appointment and did an oilchange (switched to full synthetic) & tire rotation as well first thing in the morning at 7:30 sharp.

After a few hours they're still putting away and i'm getting a little anxious. According to most people it should only take about an hour... Finally at about 11:00 they say they're just about done but now it has a 'rough idle'. I'm thinking "oh crap what did they ruin now...". They pull up the car, I start it up and if anything I think it runs BETTER than it did before - Perhaps my beefy rumble from the axle-backs has'm confused since I don't think anyone with a modded G8 has been to their service department yet. I do a quick visual take and it all looks alright so i'm off!

Driving on the freeway I definitely notice more of a high-end responsiveness that wasn't there before. Easy power pickup & acceleration across the full spectrum, even when already going *ahem* "above the speed limit".

I pop the hood to take a look at it again at the end of the day and I notice a wobble. Oh no......AAAAAAAAAAAARGH !! they DID screw up my install! I'm freaking out big time thinking about how now they'll blame the pulley if anything is wrong with the engine while it could've been their butchered installation. So i manage to take some video of it and post it on the boards and most people said: oh it's no big deal, and doing some research i found a lot of corvette owners having the same issue both stock & aftermarket.. something about belt tension and such.. Oh well.. i'll just keep my fingers crossed and hope it's good, otherwise i'll have some other shop look at it to fix it.. if I can find one!

Update: Had a corvette specialist place look at it and they said it was A-OK, so i'm happy! :D
I'll be taking my car there from now on to do any mods.

Overall I Highly recommend this mod to anyone!

Visit New Era Performance Parts Here:


  1. grandmacpubah (jesse)May 4, 2009 at 10:07 AM

    Steve what was the part # of the Gatorback? I want to do the excact same thing, but I'm have a problem finding the Gatorback equivalent to the Dayco.

  2. I'm pretty sure it was: GTR-4060747
    Number of Belt Ribs: 6
    Belt Length (in): 74.75 in.

    but i'll double check later - think I still have the package!

  3. Steve - There is no concerning regarding the stress on the engine mounts due to the wobble? Thanks - Tony.