So I put under drive pulleys on my car and a friend told me I need to piggy back the old crank pulley on the new one because it had a dampner on it. I read that the 4v motors are internally balanced and the only thing the pulley did was dampen vibration a bit. he said my motor will go to hell quick without it piggy backed but I have never heard this before with pulley swaps. Can anyone shed some light on this for me?

 

piggy back udp sux, i would not run them. the dampener looses its effectiveness if the it separated by a sandwich style pulley. if you really want udp's you might want to consider the ones that have a different crank pulley and do not require you to piggy back your o.e. dampener. a long time ago when i first got my gt i did some before and after runs with udp, about 1 hp difference.

 

I already put the underdrives pulleys on and have been driving with them. So i just am wondering if im gonna screw my motor up. I got MAC pulleys and if that helps any.

 

bump.

 

You need the damper on there. You run the risk of busting your oil pump at higher RPMs if you don't. The one-piece damper/pulley designs like Steeda, March, ATI, Innovators West are much better than the piggy-back jobs at controlling the crank vibrations.

 

So I should just buy a new one? Do they make them in different sizes so I can keep the under drive?

 

You didn't keep the stock damper?

According to the MAC install instructions you should have bolted it to the new pulley.

http://www.macperformance.com/store/...structions.pdf

 

+1 i would be very worried about slinging that oil pump apart with out a dampener considering the way it is driven.

 

I didnt read the instructions thouroughly. Im kicking myself in the *** now because they are alreeady ont he car. I still have the stock dampner but I have a feeling its gonna be a pain to attach it without taking the crank pulley off. Thanks for the info.

 

from experience, always read the instructions thoroughly and understand them before you start.