09-01-2003, 07:20 PM
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CC Member
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Join Date: Sep 2003
Location: san francisco,
Posts: 1
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Not Ranked
something a little different
OK. I have a 1968 302 w/351 heads, that's balanced and blueprinted, heads ported, decked, polished. I 'little bit of a cam', and 'roller rockers', I'm told by the seller, who had it built. Fresh motor.
First I adjust the valves using the method that John described, and I wind up w/40 - 90 lbs compression in all cylinders; not very good. Reading on, I see Perry's method, and it strikes me as easier to identify TDC on all the cylinders, so I readjust the valves Perry's way. Now I have 90 - 120 lbs compression across all eight cylinders; still not very good. Beginning to sense a pattern developing, I adjust the valves on number one cylinder one last time by Perry's method EXCEPT -- instead of continuing to tighten the valves 1/2 turn (preload) after zero clearance, I BACK OFF 1/2 turn. Check compression again: 210 lbs.
After doing all eight cylinders the same way, compression is 180 - 220 all the way around, and my motor runs like the proverbial violated simean. I mean, it's noisy, but it tachs to 6300 faster than you can say '6,300'. I'm not complaining here, but does anyone know why my motor runs best with less than zero preload on the valves?
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