Quote:
Originally Posted by Katech_Zach
If your camshaft/lifter is not on base circle (when the roller is not on the cam lobe), then it will open the valve based on where its at. You need to check on a cylinder that is set to base circle to accurately measure pushrod length.
Once you verify you are at base circle, take your pushrod measurement at 0 lash (rocker should be stocked down by hand, with the ability to move the rocker side to side, but not up and down. Add .075 to that number and round to the nearest size.
If you are at base circle already, and it is still hanging a valve open, you are unfortunately not measuring correctly, or there is something fluky going on.
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Im sure im on base, I've checked at tdc and even when one of the intake or exhaust valves are open to check the opposite one. Are the lifters suppose to compress easier then the valve spring even after being pumped up with oil?
Quote:
Originally Posted by KingLT1
Get on the base circle of the cam, use an adjustable pushrod to find zero lash, measure the adjustable pushrod end to end with a caliper. Now add the desired preload on top of the previous measurement and order the correct length pushrod.
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I did use an adjustable pushrod and got an 8inch caliper. My btr 7.80s are coming in at 7.807 tip to tip and at zero lash im at ~7.758. Im not sure if there is something im missing with the GM race lifters that have a unique quality to them.