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I bought a TFS pushrod length checker out of Summit the other day. It did not come with instructions, so I checked the Compcams website. I don't really understand all the directions.

I know I assemble the rocker arm and use the pushrod length checker as the pushrod. Do I tighten down the rocker arm? What do I look for? Just the point of the valve tip where the roller rocker rolls over? This doesn't seem really precise to me. It seems like there is a lot of room for error. Am I missing something?

Thanks, Brad.
 

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Well it could all be done without one, calculating distance traveled, and using trig to calculate the angle of sweep above and below perpendicular to the valve then perfromaing an adjustment of intial height to reduce the difference above or below perpendicular.

Or you assemble the valve train. Adjust to as near operating condition as permissable (soak hydraulic lifters in oil) set mechanical (solid) lifters as close cold as possible, and measure rocker roller travel over the valve tip. It is less important where the "contact patch" is on the valve tip. It is important that all the force is affected along the "normal" travel of the valve. That means the smallest "contact" patch on the valve tip. The adjustable pushrod (pushrod checker) lets you keep adjusting around until you get that minimum contact patch. Measure the rod, and order 16....
 

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Setting Pushrod Length

I've read 2 things that seem to make sense, the second one more so than the first.

First: (best using a light checking spring) rotate the engine thru a complete cycle after adjusting the rocker. The rocker tip should travel evenly over the tip of the valve, with mid lift about centered on the valve tip.

Second thing: because valve spring pressure increases as the valve is opened, mid lift should occur slightly before the rocker tip gets to the center of the valve stem. This seems to make sense because the opening pressure on the valve would be a little more vertical during the highest spring pressure, somewhat lessening valve stem side pressure in the guide.

Might be overkill, but what could it hurt?
 

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I usually try to assemble the valvetrain at zero lash on a hydraulic lifter with a light spring. I coat the tip of the valve with grease first, (so you can see the pattern) then assemble the valvetrain using a light spring. I then use turn the engine over once and take the rocker off to check the pattern. I like to see the pattern centered over the center of the valve stem. If it isn't adjust the pushrod shorter or longer to get the desired pattern.....
 
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