Underdrive pullies. Yay or nay?

[Brandmeister]

Opinions of underdrive pullies for the KA? What kind of hp increase would I get?

[seang]

I am interested in the bad things people have said about them because they don't have a harmonic damper.
Modified by seang at 11:03 AM 1/8/2010

[Wc240]

yes to the pulleys, but not the crank pulley

[-RJ-]

i got the light weight pulleys but not the underdrive one, im not sure if the water pump and the other pulley do anything though

[liquid_cool]

yes to the pulleys, but not the crank pulley

Wc240 again makes a great responce...but let me please add to this..

the crank pully is more or less a dampening/balencing device for your engine...it soaks up massive amounts of harmonic vibrations that is produced by the engines rotation under load...this helps the longevity of the engine by minimizing that destructive forces vibrations have on the bearings and rods...

you can get sweet looking pullys for your water pump..altinator..ps..and what not....but keep your OEM crank pully there...thats my advice...good luck..what ever you decide.

[Brandmeister]

Alright, thanks for you help guys!

[Wc240]

liquids right. the reason you get power from replacing the crank pulley is becouse its lighter. its lighter becouse it doesnt have the dampner on it. you need the dampner. the "other" pulleys are still supposed to help. by lightening them up and underdriving them (search for gear ratios/underdriving theory, not gonna type it out)

[Pirate_Freder]

actually the stock pulley on the KA is just a damper and NOT a harmonic balancer. It's pretty much just there to absorb the shock of the a/c compressor turning on.

Harmonic balancers are great if you are going for a serious build, especially a high revving one. Otherwise though, not necessary, I have an aluminum underdriven crank pulley with no problems and great performance as do many other people.

Now of course when I rebuild my engine and go high comp/high rev then I will more than likely get a harmonic balancer. Oh and also, they cost around $400-500.

[seang]

actually the stock pulley on the KA is just a damper and NOT a harmonic balancer.

Are there differences between them?

I have an aluminum underdriven crank pulley with no problems and great performance as do many other people.

How many miles have you ran it? Do you know anybody who has ran them for long periods of time, like 75,000 miles?

The reason I ask (and I'm not saying that dampers are unimportant) is that when people speak of negative things like this, they usually speak in general terms, and have not subjected their own motors to it, so it's only speculation, even if it is educated speculation. Engines, or more specifically, engine parts are unique, and some can take abuse that others can't.

Maybe we are underestimating the rigidity of the stock forged crank, and the stock damper isn't really as critical as it would be on a 500hp ka24, or a GM Iron Duke 2.5 liter (which is known to have a flimsy crank).
Modified by seang at 4:51 PM 1/13/2010

[Wc240]

actually no, its a dampner. to dampen vibrations hitting the crank shaft. the ac compressor kicking on is an insignificantt kick. barely would jarr anything.if you look up anything at all, you can see what its designed to do. dampner and harmonic balancer. two names same thing. it helps deal with resonence, vibrations the crank cant hold up to. this is why you hear tales of peaple eating up rod/main bearings(espetially the rear main) becouse when the crank damper isnt there, the vibrations(read-harmonics) needs to go somewhere. it goes to the next weakest link, the bearings.any google/bing/wiki search on this will give you plentty of info. or check out How stuff works, pretty sure youll find something

sorry, but the comment about the ac compressor just sounds like an uneducated guess. never actually researching anything.

no there isnt a difference. search and the internet will give you the answer

[ss82480]

I ran an UR underdrive crank pulley for approximately 8-9 years on my 240 with no problems. Put prolly 80-100k miles on it, changed front main seal once. Currently at 193k miles on stock bottom end, and boosted with no problems. Everyone has their own opinions.

[fiznowler]

I picked a motor and transmission set up because i needed the 5 speed about a month ago. The motor came with a lightweight pulley. I am not going to put one on my car if you decide you want to i will sell it on the cheap.