gear drive cams

[Sundance]

Mike have you seen a difference in hp/tq between chain drive cams and gear drive cams? Just curious...thanks.

[Mike]

See my reply to Zigzzagz, 996 to 995. We have not done an actual A to B test to see if hp increases are real. This would require a set of cams that are available in both gear and chain, for example Andrews TW55's. It would also require an aggresive motor to see measurable differences. It would be a fun test. The reality is we recommend gear drive based upon the valve lift and the amount of valve spring required to control it. This is typically anything over .625, lift at the valve and some cam manufacturers do not offer chain drive cams when we get into these lifts. As valve spring pressure goes up, the chance for loss of tensioner control or chain whip theoretically becomes greater. As the tappets nose over center the cam loabe load and unload, suddenly reversing the pressure on the cam. Since the cams are connected by the chain, one can affect the other in the same way and may even synchronize at certain rpm's. I.E., as one cam lobe is on the opening side another may transition from opening to closing. Now, if another lobe does this in sucsession to the first this can cause some very strange oscillations in the chains. which the tensioners hopefully can control. Another fun thing to do would be to time all these events out to see how and when the chains/lobes are loaded. Another selling point for gears is that they rerverse the direction of the rear cam causing the lobes to be opposite where they normally would be. This allows for a lot lift because we do not have to deal with lobe to lobe clearance between cams, but it would also change sequencing of lobe loading. Again, something to measure. Anyway, another long winded answer to a simple question.
Thanks for using this forum, Mike