Underdrive Pulley thoughts
 

Hey guys,
I am considering installing an underdrive pulley kit, I have the Stillen one, and I am considering doing that with a custom NST O/D for the alternator or just buying a full NST kit. Everyone in my local group says NOT to do it, and only one person has, but he doesn't DD his car like I do...

What I do need to know is:

Who has installed it?
How many miles ago?
Any changes?
Any problems to report?

This is NOT a thread to bash a particular manufacturer, and I almost do not want Stillen or NST to post unless they say they will warranty my engine if one of their products causes it to go bang...
Or if they'll pay for uninstallation/revert to stock! Lol

Underdrive crank pulley is all you need. It may give you 2 to 4 h.p, or get your engine out of balance, or both.

If all you want to do with your engine is change the pulley then listen to your buds - 2 to 4 HP isn't worth the effort.

As opposed to??? You can't go underdrive with a supercharger...

I want to under drive to get the last few horses out and up the throttle response a bit...

I'm just trying to get people's input on it

I'm using the NST set and have had no issue

I did notice a slight difference in acceleration

I've probably have about 8k on them so far

No Problems or worries

I have about 4k miles in my NST set and no issues. The diff is more like 5-10whp across the entire rpm range. my dyno is posted in the NST forum. I recommend it. Voltages stay the same and you get more power.

Anyone else?
I have always assumed that the people who have problems with it are the same guys who have problems with spacers... They don't know how to do it properly and/or they don't know what a torque wrench is...

Installed my stillen ud pulley about 8k miles ago. No issues whatsoever. I can't really say I noticed a power difference, but the throttle response definitely improved.

The problem is the potentially negative effects of undampened harmonics on the oil pump...

I've read both sides over and over. Is there anybody here who has used light weight pulleys and has had damaged that is attributed to the pulleys? If so, please speak up.

I've researched these and the Unorthodox seem to be the lightest. On their site they say that each pound lost on pulley weight is equal to 2.7 HP. That would be about 10 HP. They didn't state how that is spread across the rpm band.

Thank you for posting that!

Well, I have met Mike at NST, and he did work on my last car, and I know he know's what he's doing. So I'd personally buy from him
As for 2.7hp per pound lost, that's complete horse shite... Maybe if you lose the 4 lbs AND you dyno between A/C on and A/C off, lol

When someone can REALLY prove that to me that would be awesome... I talked to Mike at NST about this, he said yeah at like 10k+RPM's you're going to mess with the balance and the "dampener" that comes on the stock one is a .5mm thick thing of rubber... Which doesn't look like will last more than a year or 2...

Someone link the GTM write up on why pulleys are bad news.

I'd love to see that

The GTM writeup was based on an SC install where they had to remove it. The important bit there was that the Aluminum pulley had virtually welded itself to the crankshaft due to metallurgy/torque/heat over time. They had to go after it with a torch and a giant 3/4-drive torque wrench and barely got the thing off. So yeah, if you ever want to remove it easily, don't put an Aluminum pulley on the crankshaft :)

That issue aside, the other important point is if you ever plan to do an SC, you'll probably want to take it off because (a) the pulley gains are pointless at SC-gains levels, and (b) you'd have to account for it with custom SC-pulley diameters to get the intended PSI from your SC, which is a needless pain.

The harmonics thing: nobody will ever conclusively resolve that issue. It's been debated for years on so many different cars, and someone will always disagree strongly one way or the other. If there's a real harmonics issue, the oil pump is the least of your concerns. The big issue would be failed crankshaft bearings wearing them out from the excess runout from the harmonics, or total crankshaft failure at high RPM. Personally, I have yet to see a case on an engine comparable to ours where the pulley was definitely to blame for an engine failure. I'd think the numerous companies selling pulleys like this for all makes and models of performance car out there would've been sued out of existence by now if that were the case.