hi scot. i am now bussy to modifie a zen according to your article. i am a bitt unsure about the intake timeing. you dont say how much it should be. as from the article i understand you only cut the in. port a bitt wider. i really would like to get this engine running good.:diablo: thanks john

I usually run over 160 degrees. If you take about .020 off the bottom of the cylinder to get lower head clearance, you need to take about .040 off the intake side of the piston skirt for that intake timing. You can experiment with several pistons with different cuts. The limit is the loss of low rpm torque as the timing is raised.

Lohring Miller

On my builds I remove gasket completely and lightly machine dome of piston. That said, cylinder is lowered and intake duration made longer.
With .035" cut of piston intake side skirt, intake duration comes in right at @ 158* ... which I have found to be pretty optimal for oval duty race engines.
Personally feel anything above 160* is too much unless you wanting a SAW engines powerband :?