Stillen U.D. pulleys help.

BGTV8

It is not vibration per se, it is the harmonics .. I'll find a reference for you and post it here later.

Reference 1: Wikpedia on harmonics: http://en.wikipedia.org/wiki/Engine_balance
Reference 2: Coming .....

In my post I used the word "vibration" but to be strictly accurate, I should have used the word "harmonic vibration".

It is harmonic vibration that destroys OEM oil pump gears in the VQ engine above 7500rpm - I cannot find the actual engine speed as my notes are in the orifice at work - but it is around 7600-7700.

The reason I have reservations about after-market pulley kits is that no-one knows what engine speed the critical harmonics are exhibited ... and these harmonic vibrations are engine killers ...

If you want to know more, take the time to speak to Jackson Stewart at Unitech Racing as I have done several times, or Clark Steppler at JWT and I am sure they can fill you in on the details.

A flywheel is an inertia storage device, not a damper.

The purpose of the damper on the nose of the crank is to either shift the rotational frequency (engine rpm) at which catastrophic harmonics become evident out of the engine operating range, or to damp them such that they are no longer destructive.

Mate, you can disagree with me, even tell me I am a d1ck-head full of sh1t, but 40 years of motorsport and the pain and disappointment of losing 3 cranks in one season taught me a hard lesson about harmonics, and that is knowledge that I respect.

Now, the OP was told by his shop the proceed with care, and all I am doing is echoing those words of advice.

I do not know what the implications for after-market pulleys actually are - they may be totally benign (and probably are) but if the OP wants to use his vehicle on the track or strip, I am simply saying buyer beware.

There is no need to continue this thread .. because we are each accountable to ourselves for our own actions - I am not dictating to the OP, merely providing fact-based information that may, or may not, be pertinent to his post.

He (and you) are always at liberty to ignore the statements and that is your right.

As I said, tread your own path ....