Pro's\Con's Underdrive pulley
Thread Starter
Drifting
Joined: Aug 2005
Posts: 1,924
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From: CT
Pro's\Con's Underdrive pulley
Thought I put this here but it ended up in scan\tune oops.
Ok I tried searching but had no luck. What are the pro's and con's of installing an underdrive pulley and when should it be done (same time as headers that sort of thing or is it easy enough to do whenever)? Also how much of a gain could be expected on a stock 2003 Z06?
Just trying to compile all sorts of good info in prep for what I'd like to do over the next 1 to 2 years.
Thanks
Ok I tried searching but had no luck. What are the pro's and con's of installing an underdrive pulley and when should it be done (same time as headers that sort of thing or is it easy enough to do whenever)? Also how much of a gain could be expected on a stock 2003 Z06?
Just trying to compile all sorts of good info in prep for what I'd like to do over the next 1 to 2 years.
Thanks
Former Vendor
Joined: Nov 2004
Posts: 613
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The pro's to an underdrive pulley are obviously power... Usually we see 5-10 rwhp from one. The cons are that sometimes you will have charging problems... usually only cars with huge stereo's though. And they do make an "overdrive" alternator pulley to combat this, however it will take away a couple horsepower so I'd only do it unless you absolutely have to... Most of the time I've never seen anybody have a problem with an underdrive pulley, we put one on almost every car we build...
Usually the best time to install one is same time as a cam.
Chuck @ HPE
281-448-1300
Usually the best time to install one is same time as a cam.
Chuck @ HPE
281-448-1300
Former Vendor
Joined: Nov 2004
Posts: 613
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Originally Posted by Last C5
My apologies to Nulltime for adding to his thread (read hijacking) but which underdrive is the best. I've seen 10%, 20%, and 25%???
You wanted to know this anyway, right Nulltime?
You wanted to know this anyway, right Nulltime?
I usually keep them in stock.
Chuck @ HPE
281-448-1300
Thread Starter
Drifting
Joined: Aug 2005
Posts: 1,924
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From: CT
Ah cool, yeah I was wondering about the 25% and alluminum thing. Kind of guessed the Alluminum part hehe. Ah so if you were doing a cam it would be the time to do it. Ok cool thanks for that tid bit 
This calander year I'm changing out my entire exhaust system. Next I'll start to peek at the power adders uptop hehe.
This calander year I'm changing out my entire exhaust system. Next I'll start to peek at the power adders uptop hehe.
Burning Brakes
Joined: Nov 2004
Posts: 993
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From: PA
Originally Posted by Sales@HPE
ASP. It's 25% underdrive and made from aluminum. Most others are made from iron.
I usually keep them in stock.
Chuck @ HPE
281-448-1300
I usually keep them in stock.
Chuck @ HPE
281-448-1300
Melting Slicks
Joined: Nov 2003
Posts: 3,011
Likes: 9
From: Dublin GA
Originally Posted by 03Ragtop
How much has to come off the car to get the pulley off?
, Very few guys would ever do just a pulley change, but if you're doing a cam change, it's just a matter of putting on a different pulley (and belt)
The AC portion of the pulley is usually the same size by the way
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Former Vendor
Joined: Nov 2004
Posts: 613
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Originally Posted by Silver98
Chuck, I checked your website, because I was interested, and the writeup says 20%. What's the price difference, and do you have the 25% ASP aluminum underdrive?
Yeah, my website is old and feeble... I don't think it has been updated for a year and a half. I've been trying to get a new one made, but the guy I had doing it flaked out after a year. So not sure what I'm going to do about that whole situation...
Anyways, it's 25% straight off ASP's website. https://www.aspracing.com/ezRetail/s...php?msg_id=273
We sell the whole kit with belts and a new crank balancer bolt for 289.95.
Chuck @ HPE
281-448-1300
Burning Brakes
Joined: Apr 2005
Posts: 1,081
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From: Bear Delaware
I went with an ASP pulley during an intake manifold change and header install. It's been about a year and I've had no problems at all. The voltmeter showed maybe a 1 or 1.5 volt drop. Still putting out about 13.5 volts though so no problems.
Thats the best. Never had any issues.
I have a 12" sub and a 500 watt amp is that going to affect the ability for the underdrive pulley to work effectively?
Racer
Joined: Jun 2004
Posts: 433
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From: Brookfield WI
Originally Posted by MTurnbo
I went with an ASP pulley during an intake manifold change and header install. It's been about a year and I've had no problems at all. The voltmeter showed maybe a 1 or 1.5 volt drop. Still putting out about 13.5 volts though so no problems.
Team Owner
Joined: May 2005
Posts: 23,682
Likes: 9
From: Flagstaff Az.
UD pulley
The only time the ud pulley causes problens is during idle. As soon as you speed up the engine the power output goes up to normal. As stated above with A/C on and a big amp you will sometimes see the ammeter showing a lower number at idle. Its a good idea to pin the crank when you install the pulley.
Team Owner
Joined: Jun 1999
Posts: 71,447
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From: Miami bound
CI 4-5-6-7 Veteran
Originally Posted by BOTTLE FED
Steering rack ,
Very few guys would ever do just a pulley change, but if you're doing a cam change, it's just a matter of putting on a different pulley (and belt)
The AC portion of the pulley is usually the same size by the way
, Very few guys would ever do just a pulley change, but if you're doing a cam change, it's just a matter of putting on a different pulley (and belt)
The AC portion of the pulley is usually the same size by the way
Race Director
Joined: Mar 2004
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From: Fort Wayne IN
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Originally Posted by tiojames
Its a good idea to pin the crank when you install the pulley.
