Quote Originally Posted by tomtom123 View Post
I have a 1999gtp. I have to replace the head gasket and then put the top back together and then measure for knock before I do a pulley drop =P
Before the head gasket went I was seeing 0° of knock and then every once in a while see a spike up to 5.8ish for less than a second. Usually it was around .6 seconds. So I feel its safe to drop to a 3.6 or even possibly a 3.5" pulley safely and obviously measure for knock again. I've replaced the downpipe, not headers though. Was told if theres no knock, a downpipe can get you away with a 3.6" or possibly even a 3.5" pulley. Since I've been seeing 0° with a stock tune and stock engine with a ZZP downpipe, I think I could tune it and run a 3.5" =P
tomtom123--

A spike of 5.8* for less than a second, especially on a stock tune, is indicative of false knock. Check to make sure there's no metal-on-metal contact, such as the sway bar hitting the downpipe, headers hitting the transmission dipstick, knock sensors going bad, etc.

Get yourself an open cone intake as well and then you should be ok in the 3.5 range. Get a tune, bar none... a good tune is the best mod in my opinion.