Thread: Push Rod length

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I tried to keep all my posts to one thread but it doesn't get much response (except from you Pat ). So I'll try it again to see if I'm on the right track, I'm not really sure I understood your way Pat I tend to need pictures to help me.

I consulted this link that shows the checker I bought from Summit.

http://www.thedirtforum.com/pushrodlengths.htm

From this I got my max lift of .48 subtracted from .60 is .12, divided by 3 gives me .04 gap. With the preload adjustment of .021 My total is .061" total.

So I measured with the lifter fully down but not compressed and I have a gap between the pushrod and the measuring tool of .039. So I guess that means my pushrods are .039" too short??? I went today and bought .05 over and installed them on four of the lifters. The roller looks to be just slightly in from center on the valve when the lifter is all the way in and just slightly out at max lift. The directions with my AFR heads say stock should work but up to .1 over might be required. Does this sound like I'm doing it right??

Spent two hours today taking out the inner springs for the break-in. Had to use an old leaf spring with a hole drilled in it and cut a slot in the end, ground it up shiney and it worked like a charm. I think I'll go buy the proper tool to put them back in, that usually means I'll never have to use it again .

Here it is so far. Oh yea this is for a Comp hydraulic flat tappet cam.

Thanks,
Sean

Sean, I think what Pat was sayin' is that the checker you're using might work differently rocker to rocker, as he has gotten different results using using it and prefers not to use it any longer. Apparently he uses the same method most of us use and that is to verify that the rocker tip travels through its arc making the shortest possible trip across the valve tip and the extremes to the intake side and the exhaust side are equal.

The rocker changes its effective ratio as it swings through its arc. The ideal setup would be: Starting off at zero lift with the rocker tip on the intake manifold side of the valve, then moving to the exhaust manifold side of the valve at mid-lift, then coming back to the intake side of the valve at full lift. On the return trip to zero lift, the roller would cross the center of the valve tip and go to the exhaust side of the motor at mid-lift, then back to the intake side of the motor with the valve back on its seat. In this way, the rocker would be at its longest effective length halfway through the lifting of the valve. Its effective length would be shorter at both zero and full lift.

Whether you're using an adjustable checking pushrod or a pushrod that you think might work correctly, de-grease the valve stem tip and color it with a black Sharpie pen. Then, install the pushrod and rocker arm while the lifter is on the base circle of the cam. With hydraulic lifters, jiggle the pushrod up and down while tightening the adjusting nut until all play is removed. Twisting the pushrod with your finger and thumb will not work. You'll be compressing the spring and not even know it. Jiggle the pushrod up and down to remove play. With all play removed, tighten down the rocker adjusting nut to your normal preload. Using a socket on the damper retainer bolt head at the front of the crankshaft and long bar for leverage, turn the motor over several times clockwise. Obviously this is more easily done if the spark plugs are out of the heads. Remove the rocker and check the mark left on the valve tip. The roller tip on the rocker should leave a shiny spot in the center of the valve tip where it wore away the ink you put on the valve tip. The width of the shiny area will tell you the intake side to exhaust side extremes of travel of the rocker tip across the valve tip. Measure this width with your dial caliper and record it in your toolbox notebook.

If the pushrod length is correct, this mark should be centered across the valve stem. If it's too high (closer to the intake manifold), try a slightly longer pushrod. If it's too low (closer to the exhaust manifold), try a slightly shorter pushrod. This method works well when using an adjustable checking pushrod.

Good explanation by Richard. Here's a pic to see what he was describing.

Thanks for the info.

That looks to be exactly what I'm gettin' with the .05 over pushrods , although not to that extreme but I guess that's just for the picture clarity. I'll tighten the rest in when I get back from work and rotate the engine over a bunch of times watching the roller tip.

They might look off in the picture cuase the nuts are just threaded on loosley.


Thanks again,
Sean

see i can take the day off you are in more then capable hand with Tech and Nitro. like tech said i did use that type of checker but it just was not as good as i could get so and would not work with shaft rockers like T&D or jesles i use the ferry head checker that works off mid lift 1/2 roller tip and 1/2 the valve stem and you use the checker that tells you were you need to be at the same can be done with a marker or layout blueing or yellow oxide oil past paint that can be pick up at a hobby shop and a one 1inch dial indicator mark your valve stem roll over to mild lift and pull your rocker off and look at the photo of the rocker that nitro posted and go from there i go over all my engines i build with my checker and get the size push rods i need for the job i loose money doing it were other guys may not spend so much time on it but i think it is one of the most crucial part of a engine build when you use after market heads rockers small base cam deck block cut heads longer valves or short valves to