Internal and a few exhaust part pics

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12-27-07, 07:57 PM

#31

carchitect

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Quote:

Originally Posted by Gernby

I disagree about the difference in performance that can occur from a few thousanths of an inch of clearance. The first time I adjusted the valves in my S2000, I accidentally set the clearance by mearsuring between the cam lobe and roller rocker. This meant that my clearances wound up being about .003" too large. There were some interesting changes to the sound of the engine at WOT, and the VTEC kick was much more pronounced. Unfortunately, when I attended an S2000 club dyno day, my low end power was significantly lower than everyone else's. After discovering my error and fixing it, my dyno's looked like everyone else's again.

My belief is that Honda specs their clearances really high to give it a 100K service interval. I find it hard to believe that the S2000 really needs the .008" for the intake valves and .009" for the exhaust. I ran .001" below minimum spec for years without problems

Ah..It could develop a loss in power on Vtec engines on the low lift cam since the low speed cam has 1 intake valve that opens a lot less than the other. On the high speed cam the increased lift and duration are provided from the middle rocker and the lash or clearance won't make any difference. That could explain your loss on the low end.The difference in lift creates a swirl in the chamber boosting torque. Changing the clearance could change the swirl effect in there and could change the behaviour of the power delivery. BTW, the first intake valve that I found burned was on a 92 NSX when I worked for Acura. It was from being adjusted too tight. Those cars are so difficult to work on that you practically do your adjustments by osmosis rather than looking at it. On our supras we haven't noticed any difference in any part of the dyno graph after a lash adjustment if it has with aftermarket cams. Most of us won't reuse the OEM cams. Once they come out usually HKS bump sticks will replace them.