WTB: 89-95 UDP Under Drive Pulley

[SHO_POWER]

Looking for UDP for my 1991 SHO.....I live in Canada so if it's in Canada that's a bonus if not I can have it shipped to my US address.

 

[chrism3784]

DON'T, leave it alone. I put an UDP in my 90. After about 6k miles my crank literally snapped in half while driving home on a vacation. A normal pulley has a rubber inbetween the metal to cusion vibrations from the belt drive. the UDP does not, its a sold, cheap metal and will send all belt vibrations to the crank. May be fine, may not. Don't waste your money, it made no difference in my gas mileage. Also when idling it will run hot on a summer day. Seen the H a few times and had to rev a little to cool it.

 

[Jesse Menck]

I have a 4 piece. And have spun it all to 8000rpms.

 

[Jesse Menck]

There was a 2 piece crank pulley that was known to separate

 

[Irish Pride]

I have had an UDP on my 91 for 30k plus miles with no issues. Never has it run hot. Never have I had any charging issues. The throttle response improvement was very noticeable.

The Yamaha V6 is internally balanced. It doesn't require a balancer. The SHO crank is capable of 500+ HP. I'm not doubting that your crank snapped, but it didn't snap because you had an UDP on it. Something else was going on.

 

[chrism3784]

I just don't trust them. Had 130k miles no problem before. 6k after putting a UDP in snaps. I don't believe in coincidences

 

[zak]

Pretty sure by early 2000s SHOshop had stopped using the underdrive crank pulley and instead offered larger alternator, power steering and water pump pulleys (what I bought from them for my 95 around 1999 or so).

The issue is the factory pulley has a rubber vibration damper built into it, the aftermarket underdrive crank pulley did not. Vibratory fatigue of metals is a well known phenomena, and is worse on the supercharged cars where greater twisting is being put into the crank.

 

[RonPorter]

I had the original full UDP MTX set from the SHO Shop installed in late 96. The engine was pulled from the rusty hulk about 125k later, and those pulleys were still going strong. The UDPs and the y-pipe are the two best mods to do. I got a noticeable throttle feel and torque increase throughout the Rev range, as well as increased gas mileage.