[HWYSTR455]

Originally Posted by grivera

Near the 7:09 mark, he rotates the poly-lock 7.1 turns, which moves the rocker off the established 90 degrees. At 8:04, he says you lower (unseat) the valve to re-establish 90 degrees. I believe the point of the light spring is so you can verify your measurements as he does at end of the video when he rotates the cam to the half lift point to illustrate the rocker is at 90 degrees to the valve.

Yeah I guess you could verify your measurements with a dial gauge on the rocker and move it to half lift with the adj pushrod in place if you want to be double sure. But the fraction you might be off by turning the poly lock is so small, it's not going to make a difference. And pushrods generally come in .050 increments as he mentions, so it's not going to be dead-nuts on regardless.

Usually pushrods are measured during an initial assembly, along with a number of other measurements. And think that's why in that particular video there's a checker spring on there. Like when you go to degree the cam and you still have it setup with the spring and pushrod in place. That gives you an op to verify open/close events, and determine true half lift of the cam/lobe.

If you want to get real technical, you would have to have the head gasket on there too when you measure (does not appear to be the case with the example vid). Or you can account for it when ordering pushrods. Like if you plan on using a .039 thick head gasket, you can add that to the length of pushrod you plan to order.

I've measured for pushrods when an engine is all together and in the car. I remove the locking nut from the adjuster pushrod so it doesn't hang up on the guide plate, and mark a line across the upper & lower halves. Can also wrap a piece of tape on it to keep it from moving when handling during removal.

Obviously you can't do the after check when you do it that way unless you have solid lifters, just be as accurate as you can when measuring.

Many people have a machine shop or builder assemble the heads, so it's a pain to have to swap over to a checker spring. So skipping the double-check usually occurs. Same for people who swap cams, lifters, and/or rockers, not doing the double-check.


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