OBX Underdrive crank pulley doesnt fit

rakkasan

rakkasan

Currahee!!
Mar 31, 2005
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RIPDOTCOM said:
got it, just took a tiny bit off the pulley where the woodruff key goes and it fit like a champ, thanks for the votes of confidence.
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Buy a new woodruff key & use the stock Harmonic Dampner or you will screw up your motor, mainly the crank bearings. Do a search for further info.
 
Mr.PFloyd

Mr.PFloyd

I am the Super Devil
Jun 22, 2005
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omg do not use a file for your crank. Some shop did it to my bros car, and well now they have a 1500 dollar bill on them to help pay for my bros 1J lol.
 
DaSuprawolf

DaSuprawolf

Im SICK of N/A
Dec 29, 2005
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i just wanna see the expirence first hand on the damage it ill do to the 7m, i fully understand the risk of an un-dampend engine, expesially a inline 6, but everyone just says "dont do it" well let him try it and if it distroyes his engine, then he can let us know and THEN well know not to use them, if not, well good for him.
 
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figgie

Supramania Contributor
Mar 30, 2005
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supra88boy said:
i just wanna see the expirence first hand on the damage it ill do to the 7m, i fully understand the risk of an un-dampend engine, expesially a inline 6, but everyone just says "dont do it" well let him try it and if it distroyes his engine, then he can let us know and THEN well know not to use them, if not, well good for him.
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hence me taking out the popcorn and waiting with great anticipation :)
 
R

RIPDOTCOM

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May 22, 2005
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Well that was informative. I have used aftermarket pulleys on different cars for years with only positive results. I wish I had done more research on the 7mge crank length before doing this. Looks like its a problem for Subaru Boxer engines as well. Being a BMW owner , I always heard that inline 6 engines were extremely well balanced. Anyway, its on now and wether it stays on is questionable. I could see how the vibration would be a factor in high powered turbo supras (which seem to be the only ones with bottom end failure related to underdrive pulleys) I just cant imagine a massive vibration increase in my paltry 200hp NA. Thanks for the advice.
 
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figgie

Supramania Contributor
Mar 30, 2005
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RIPDOTCOM said:
Well that was informative. I have used aftermarket pulleys on different cars for years with only positive results. I wish I had done more research on the 7mge crank length before doing this. Looks like its a problem for Subaru Boxer engines as well. Being a BMW owner , I always heard that inline 6 engines were extremely well balanced. Anyway, its on now and wether it stays on is questionable. I could see how the vibration would be a factor in high powered turbo supras (which seem to be the only ones with bottom end failure related to underdrive pulleys) I just cant imagine a massive vibration increase in my paltry 200hp NA. Thanks for the advice.
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it has nothing to do with balancing :)

you can have the entrie thing balanced to zero grams. That will help if you are just spinning the motor without any combustion process.

here is a copy from SF from Flubyx :)

flubyux2 said:
the harmonic damper isnt there to serve as an external balancer because someone feels that the motors arent sufficiently balanced internally. the toyota engines are internally balanced and need no external balancer. keep in mind, this is not a harmonic BALANCER, its a harmonic DAMPER. i dont care what engine you have... except a rotary... any otto-cycle, internal combustion engine WILL have torsional harmonics in the reciprocating mass. the inherent energy transfer traits of the combustion stroke w/ the onset of power delivery is what creates this harmonic vibration. when the power stroke occurs, it bends the crank, not permanently, but temporarily. there is a slight elasticity of the crank and it bends during every power stroke. after the onset of power delivery due to the power stroke, the crank recoils and snaps back. "For every action, there is an equal and opposite reaction". this means if the power stroke bends the crank 2* forward, it will recoil after the power subsides and bend back -2* the other way. its this bending and recoiling of the crankshaft that creates the harmonic vibration which needs to be absorbed by a mass somehwere on the crank assy. this mass will quell the vibrations and prevent it from transferring into other engine parts, mainly Other reciprocating parts attached to the same crankshaft which are not in the power stroke or immediately after the power stroke.

just because your engine hasnt failed yet doesnt mean that its Not experiencing harmonic vibration which could damage it later down the road. thats like saying "ive smoked cigarettes/crack/heroin/etc for 32 years and im not dead yet... therefore its not bad". come on now... lets be serious for once.
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bigaaron

bigaaron

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Apr 12, 2005
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Why "underdrive" your accessory items with a lightened crank pulley?

Possible reasons:

1) You don't want your battery to charge at idle.

2) Your 12k rpm redline is way too high for your ps pump.

3) The 7m mechanical fan is far too efficent, it should be slowed down so it doesn't cool as well, to compliment your horsepower increase.

4) OBX FTW TE HOTNESS. :evil2:

5) You hate your NA motor and want it to die as soon as possible so you can go turbo!

6) The I6 is balanced far too well with the stock dampener, and you want to FEEL your engine while you drive.
 
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RIPDOTCOM

New Member
May 22, 2005
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bigaaron said:
Why "underdrive" your accessory items with a lightened crank pulley?

Possible reasons:

1) You don't want your battery to charge at idle.

2) Your 12k rpm redline is way too high for your ps pump.

3) The 7m mechanical fan is far too efficent, it should be slowed down so it doesn't cool as well, to compliment your horsepower increase.

4) OBX FTW TE HOTNESS. :evil2:

5) You hate your NA motor and want it to die as soon as possible so you can go turbo!

6) The I6 is balanced far too well with the stock dampener, and you want to FEEL your engine while you drive.
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I wasnt doing it for any of those reasons. Just trying to reduce rotating mass. As for theFan , I use Flexalite, Didnt know I could redline at 12k, I think the alternator can keep up with 100 Watts in light and a 100W stereo, #4? I doubt #5 is a good reason and I do admit you have a point on #6
 
bigaaron

bigaaron

Supramania Contributor
Apr 12, 2005
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:biglaugh: at least you can laugh about it :biglaugh:

PS: to hit the 12k redline you have to get it going about 70, put it in first, and let out the clutch!
(this is a joke, please do not try this at home)

<edit IJ> And duck ;)
 
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