Generation III External Engine LS1 | LS6 | Bolt-Ons | Intakes | Exhaust | Ignition | Accessories
Sponsored by:
Sponsored by:

Underdrive Pulley(s)

Thread Tools
 
Search this Thread
 
Old Apr 21, 2011 | 01:21 PM
  #1  
RyanAndyBob's Avatar
Thread Starter
On The Tree
iTrader: (4)
 
Joined: Aug 2007
Posts: 123
Likes: 0
From: Louisville, KY
Default Underdrive Pulley(s)

When changing the size of a Underdrive Crank Pulley and reducing by 25%, is it required to change your alternator pulley to an overdrive pulley to bring alternator speeds back to near stock levels, or can you also reduce with a underdrive on it as well and further free up Horsepower??

This is for a 99 Auto TA
Reply
Old Apr 21, 2011 | 06:30 PM
  #2  
ULTIMATEORANGESS's Avatar
TECH Senior Member
20 Year Member
iTrader: (4)
 
Joined: Mar 2003
Posts: 10,985
Likes: 23
From: eatontown,nj
Default

i only have a crank pulley and have no problems.
Reply
Old Apr 21, 2011 | 06:46 PM
  #3  
BirdsSince16's Avatar
TECH Enthusiast
iTrader: (3)
 
Joined: Jun 2009
Posts: 535
Likes: 1
From: Honolulu, HI
Default

Same here.
Reply
Old Apr 21, 2011 | 08:02 PM
  #4  
soundengineer's Avatar
8 Second Club
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (16)
 
Joined: Jul 2003
Posts: 4,651
Likes: 17
From: Chicago IL
Default

I had issues with the Alternator....
way to tell is if your voltage output starts high at startup and doesnt drop, then you have issues and will be soon replacing a battery and an alternator..
also if you start to see things flicker, then you have an issue that needs teh alternator overdrive pulley
personally, I needed it..and its all of $25...and easy to put on and doesnt hurt your performance any.. if anything it ensure you have good voltage which will help with stable performance.
Reply
Old Apr 22, 2011 | 06:51 PM
  #5  
rio95cobra's Avatar
TECH Regular
iTrader: (3)
 
Joined: Jun 2008
Posts: 465
Likes: 0
From: Atlanta
Default

I'm kind of confused... when swapping crank pulleys, wouldn't you want an OVERdrive pulley so it will spin faster?? It seems like if you were to put an underdrive crank pulley on, you would be slowing down the crank by adding more rotation and therefore losing power. Or do I have all this backwards? Please explain
Reply
Old Apr 22, 2011 | 07:20 PM
  #6  
soundengineer's Avatar
8 Second Club
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (16)
 
Joined: Jul 2003
Posts: 4,651
Likes: 17
From: Chicago IL
Default

Originally Posted by rio95cobra
I'm kind of confused... when swapping crank pulleys, wouldn't you want an OVERdrive pulley so it will spin faster?? It seems like if you were to put an underdrive crank pulley on, you would be slowing down the crank by adding more rotation and therefore losing power. Or do I have all this backwards? Please explain
Underdrive pulleys make the accessories turn slower..
accessories create parasitic loss...
slower turning accessories = less parasitic loss = more horsepower to the rear wheels.

overdrive for the alternator makes it spin back at original speeds allowing proper charging...
Reply
Old Apr 23, 2011 | 04:42 AM
  #7  
chevy9s9s's Avatar
Teching In
 
Joined: Oct 2009
Posts: 21
Likes: 0
From: Ventura, CA
Default

remove AC compressor and belt. who needs a/c?
Reply
Old Apr 23, 2011 | 01:38 PM
  #8  
RyanAndyBob's Avatar
Thread Starter
On The Tree
iTrader: (4)
 
Joined: Aug 2007
Posts: 123
Likes: 0
From: Louisville, KY
Default

Okay. I was really worried about killing my battery/alternator. did you lose much/any of the HP gains from going from just the underdrive crank to adding the overrive alt. pulley?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Apr 23, 2011 | 04:44 PM
  #9  
shorty(98TA)'s Avatar
TECH Apprentice
 
Joined: Mar 2011
Posts: 392
Likes: 0
From: osawatomie ks
Default

Originally Posted by chevy9s9s
remove AC compressor and belt. who needs a/c?
I DO...
im not driving around in the kansas summer heat with 70% plus humidity and no a/c
Reply
Old Apr 23, 2011 | 10:57 PM
  #10  
dr_whigham's Avatar
The Scammer Hammer
Veteran: Marine Corps
15 Year Member
Photogenic
Liked
iTrader: (49)
 
Joined: Apr 2009
Posts: 6,717
Likes: 24
From: Lafayette, LA
Default

Think that's bad; Come to Louisiana... I've debated it though, as it seems my compressor has **** the bed.

I REALLY want the chrs1313 non-a/c, but the heat and humidity here is INSANE!
Reply
Old Apr 24, 2011 | 12:57 AM
  #11  
BirdsSince16's Avatar
TECH Enthusiast
iTrader: (3)
 
Joined: Jun 2009
Posts: 535
Likes: 1
From: Honolulu, HI
Default

Alabama summers. 100* heat and 90%+ humidity. T-tops can only do so much.
Reply
Old Apr 24, 2011 | 08:42 PM
  #12  
Fb0dy0nly's Avatar
TECH Fanatic
iTrader: (10)
 
Joined: Aug 2006
Posts: 1,490
Likes: 2
From: Detroit ROCK City
Default

Originally Posted by BirdsSince16
Alabama summers. 100* heat and 90%+ humidity. T-tops can only do so much.
yeah MI aint much better; the worst is getting stuck in a traffic jam with the ttops off so it makes putting the AC on pointless but then you end up the sweaty back and *** man when you get to your destination(esp with leather seats)...blah
some people dont mind tho, ive just been so used to not having ac at my fingertips that I forget to even use it most times in the bird.
Reply
Old Apr 24, 2011 | 11:01 PM
  #13  
BirdsSince16's Avatar
TECH Enthusiast
iTrader: (3)
 
Joined: Jun 2009
Posts: 535
Likes: 1
From: Honolulu, HI
Default

I usually don't have a lot of problems with traffic around here, but when I do it always seems to be on the days I'm wearing my suit. Sure I don't have my jacket on, but the long sleeved dark shirts and high collars are murder.
Reply
Old Apr 24, 2011 | 11:26 PM
  #14  
anthony.fatica's Avatar
On The Tree
iTrader: (10)
 
Joined: Apr 2010
Posts: 144
Likes: 1
Default

My car is my DD so I drive it in the rain too. So 90 degrees and rain means tops stay on and no AC would be hell!
Reply
Old Apr 25, 2011 | 12:15 AM
  #15  
soundengineer's Avatar
8 Second Club
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (16)
 
Joined: Jul 2003
Posts: 4,651
Likes: 17
From: Chicago IL
Default

Originally Posted by RyanAndyBob
Okay. I was really worried about killing my battery/alternator. did you lose much/any of the HP gains from going from just the underdrive crank to adding the overrive alt. pulley?
My main thought is if I change both, will I be about the same as where I was with the stock pulleys?
think of it this way...
you can take away 25% of the drag from all your accessories combined..
the overdrive pulley for your alternator is the smallest of the pulleys and wingdings that are spinning... you wont see any loss from the small amount of lag the alternator would cause...

where the underdrive pulley helps with gaining you power is the Water pump and the AC as they are both very parasitic.

you can gain almost as much from the underdrive pulley as you can get from switching to an electric water pump
Reply
Old Apr 25, 2011 | 07:39 AM
  #16  
ramairetransam's Avatar
TECH Junkie
20 Year Member
Photogenic
Photoriffic
iTrader: (18)
 
Joined: Aug 2005
Posts: 3,462
Likes: 75
From: Amsterdam Ny, the good part
Default

Originally Posted by chevy9s9s
remove AC compressor and belt. who needs a/c?
me too thats a terrible idea, even here in ny i need ac . I had no ac on my last fbody and hated driving it around for that reason .
Reply
Old Apr 25, 2011 | 07:10 PM
  #17  
RyanAndyBob's Avatar
Thread Starter
On The Tree
iTrader: (4)
 
Joined: Aug 2007
Posts: 123
Likes: 0
From: Louisville, KY
Default

Originally Posted by soundengineer
think of it this way...
you can take away 25% of the drag from all your accessories combined..
the overdrive pulley for your alternator is the smallest of the pulleys and wingdings that are spinning... you wont see any loss from the small amount of lag the alternator would cause...

where the underdrive pulley helps with gaining you power is the Water pump and the AC as they are both very parasitic.

you can gain almost as much from the underdrive pulley as you can get from switching to an electric water pump
Thanks Soundengineer for writing informative information. So, just to clear everything up, it would be best to get the dual pulley set up to be on the safe side and a electric water pump? (no way will AC ever go away)
Reply
Old Apr 27, 2011 | 04:39 PM
  #18  
shorty(98TA)'s Avatar
TECH Apprentice
 
Joined: Mar 2011
Posts: 392
Likes: 0
From: osawatomie ks
Default

Yeah sorry RyanAndyBob didnt mean to hijack your thread like that with my a/c comment
Reply
Old Apr 28, 2011 | 07:08 AM
  #19  
RyanAndyBob's Avatar
Thread Starter
On The Tree
iTrader: (4)
 
Joined: Aug 2007
Posts: 123
Likes: 0
From: Louisville, KY
Default

It happens
Reply
Old Apr 28, 2011 | 07:31 AM
  #20  
TRANS-DAD's Avatar
Launching!
iTrader: (1)
 
Joined: Mar 2008
Posts: 281
Likes: 0
From: PASADENA,TX.
Default

I think it's only a prob. on some auto cars?...... & all m6 cars that I know of w/underdrive have no prob.
Reply



All times are GMT -5. The time now is 12:04 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE