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Old 11-17-2011, 10:12 PM   #7
Greg Reimer 7376
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Cool Re: Valve train geometry?

Quote:
Originally Posted by buzzinhalfdozen View Post
Ok I know this has been discussed but I'm working on my engine after having all the seats in both heads replaced. Now figuring that my stem heights, and seat depths would be moved I decided I'd better do some checking on this thing figuring my piston to valve clearence may have changed.Well when I put the rocker stand at the correct height, as per T&D's instructions which I had followed in the past I'm seeing .025 inch less lift at the valve and my roller swipe pattern on the valve tip is WIDE over .200 inch. This seemed odd to me so I put the stand back to the height I had always run it which is about .090 lower, now I'm seeing the correct lift at the valve and my swipe pattern is less than .100 wide near tip center. With the stand raised the pattern looks OK till over half lift then it start running hard to the int. side. What the heck am I seeing here and why would moving the stand lower than it should be cause this change? I'm using adjustable pushrods for this setup, maintaing 1 turn from seated on the rocker adjuster screw. What gives? Since I'm not an engine builder I need some feed back from some of the pros. Thanks for any replies. Joe
Been busy this last weekend and week with Pomona and work, etc,and had time to read your thread. Seems to me that new valve seats would raise the seat, establishing a new parameter in valve train geometry. The valve stem would not protrude out of the valve guide as far,so the rocker arm shaft would be in effect,higher than it was before,thereby altering your valve stem tip contact pattern,and causing the lift and contact pattern to change. You said that you then lowered the shaft centerline,and the valve lift and the contact pattern assumed a more favorable attitude, then your change showed that you are moving in the right direction.Can you move the rocker arm shaft lower and check it again and find some more improvement?
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