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B20 rocker geometry correction + little amazon film 120-130

posted by  someone claiming to be Stefan on  Mon May 24 10:16 CST 2004 [RELATED]

Hello,

I just installed 1.6 ratio roller rockers on my B20.
To do a decent job I took a look at the rocker/valve geometry, which in my opinion isn't correct if you are running a cam with a little more lift than the stock stick.
The valve stems are 41mm above the deck of the head, the center of the rocker shaft is 38mm above the deck of the head. So that means for a valve lift of 6mm the movement of the line between the top of the valve stem and the center of the shaft is symmetrical around the horizontal plane. Which in my opinion minimizes friction on the valve stems and guides.
I have a Kent cam, with the roller rockers it lifts 11.2mm, so I want the shaft at 41mm-5.6mm= 35.4mm. That means shortening the shaft stands by 2.6mm.

I think many of you running IPD street performance cams with high lift or other high lift cams like the F, R or S cams could improve the geometry like this. I even think a D or K cam could benefit from a slight correction of the rocker shaft height.

I milled down the shaft stands with good results, the valvetrain seems more silent with the rollers and changed geometry, altough the valve lash is set exactly the same. A few extra horses seem to be present, and it seems to revv much happier past 6000rpm. Nice !!!

For those interested, someone filmed (verrrry amateuristic) me tesdriving my amazon, I have it in a 2mb avi file, nice roaring sound and grippy 16 inch tires ;-)

CU

Stefan





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