too much compression

[BigT00]

Hey Mike,
My buddy had a local shop repair top end oil leaks and bump up the compression at the same time on hir 1994 EVO softail. They used 10.5:1 pistons with stock EVO heads and springs and EV-27 cam that has a 36 degree intake close. I never heard a bike ping/knock as loud as this one when starting out from a stop. He has a DYNA 2000i ignition already set on curve 4. From what I have been reading the VOES switch can be adjusted to help but it seems to me either the pistons or cam has to go also. The bike is a 80" softail with 400lbs of rider & passenger weight. Do you think it's possible to lower the corrected CR with a later intake close cam to stop the engine knock and not have the bike a total slug at lower RPM?

[Mike]

10.5 is the limit for the 27 cams and tuning has to be spot on, as well as fuel quality. The pinging is killing any low end gains your are trying to get with the compression, so correcting that may be in order and if not corrected will damage engine parts. You could try more tuning first but I agree that adding some cam timing would be a better choice. The EV 46 has work well in the past with that compression or possibly the 51. Along with correct tuning, you'll make more power everywhere vs detuning the current setup to solve pinging.
Mike

[BigT00]

Mike,
What is your opinion on the Woods W-7 cam with a 46 degree intake close and 248/248 duration for this application? From reading the manufacture?s cam specs there are very few choice for "bolt-in" cams for that will rectify this problem. Tom

[Mike]

Good cam, but may be a little too much making the motor lazy down low or requiring more rpm's to make power.
The EV 46 is a bolt-in but the 51 should have valve to piston checked due to higher TDC's.
Mike