underdrive pulley ?
Thread Starter
Banned
Joined: Dec 2005
Posts: 265
Likes: 1
From: pittsburgh,pa
underdrive pulley ? i know this might have been asked plenty of times but.... are they worth it? and why do some only have the crank pulley? whats the differance with/without the altinator pulley? this is the only bolt on i have left to do for the engine and i'd like to know if they are worth getting or if the're dead weight on the crank snout?
Originally Posted by silverlt1ss
i know this might have been asked plenty of times but.... are they worth it? and why do some only have the crank pulley? whats the differance with/without the altinator pulley? this is the only bolt on i have left to do for the engine and i'd like to know if they are worth getting or if the're dead weight on the crank snout?
On The Tree
Joined: Mar 2006
Posts: 148
Likes: 0
From: Stillwater, OK
you dont really see a gain in hp because you have to put the stock crank pulley back on i believe because it is the harmonic balancer also. so you can run the smaller pulley but you still need the stocker so personally i feel theyre not that great of an investment.
Without the smaller alternator pulley the alternator shaft spins slower, meaning less voltage, and the voltage jumps around and can drop pretty low
With it the voltage stays closer to stock.
With it the voltage stays closer to stock.
I have a 34% underdrive setup in my car. You unbolt the Harmonic Balancer off, which is also the stock crank pulley, and you bolt the underdrive pulley, then the balancer back on with the bolts. The Balancer will go over the underdrive pulley. I have a High-Output Altenator, and I usually run higher RPM's with the 3.73's, so there was no difference in electrical power. All I needed was a shorter belt. I have no AC, took it out. The engine will get up in RPM's faster. IMO, every little bit helps.
I purchased the set for my car. At first, I ran only the crank pulley. While idling at the strip, the battery discharged enough that the car died and had to be jumped. After I installed the alternator overdrive pulley, I have not encountered any more problems. The power steering and air conditioner are now underdriven. The steering has more effort at low speeds, but is not a problem.
Power increase was slight, but every little bit helps.
Power increase was slight, but every little bit helps.
IMO these piggyback pullies are a bad idea, you are adding rotating mass and moving the damper away from what it needs to dampen. That said a stock car might have issues with just an UD crank pulley but no alt. pulley, but a cammed car with a bumped idle will likely be just fine.
The right way to do this would be to get something like the lighter ATI, better, lighter , rebuildable dampening with the UD, it aint cheap though.
The right way to do this would be to get something like the lighter ATI, better, lighter , rebuildable dampening with the UD, it aint cheap though.
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