blndweasel

Hey all,

I just bought a new motor. It's got a high lift cam and hydraulic lifters, with 1.6 ratio roller rockers. I need to know what the proper procedure is for choosing pushrod length. i have an adjustible pushrod length checker. I have heard conflicting stories about how to determine the proper length.

This is what I have pieced together so far:
I set the pushrod length checker to standard length to start out, and crank down the rocker nut until the pushrod stops turning freely. Then I turn the rocker nut 1/2 turn more in order to achieve approx .025" preload on the hydraulic lifters.

what I don't understand with this method is how do i come up with a pushrod length other than standard? any advice would be greatly appreciated.

PatsLs1vette

Ok now that you did that turn the motor over by hand and watch the rocker tip it should ride in the center of the valve,up and down to be right.Different things can make the geometry change,block decked ,shaved heads,cam profiles.YOu want to the rocker arm to ride as close to center of the valve stem as possible to have the right geometry.


[Modified by patsnitrovette, 5:17 PM 1/22/2003]

Pete79L82

It helps to take a black magic marker and paint the top of the valve stem first. That will make it easier to see the contact patttern.

The longer the pushrod, the closer the contact point will move to the rocker stud.

The shorter the pushrod, the closer the contact pont will move to the exhaust manifold.

You want the contact point to be in the center of the valve stem.

Lt1er

You have been given good advice by each of the replies. With the parts you stated .100 over is @ what your going to end up needing.

blndweasel

Thanks much for your comments on this subject.

I managed to also find some great documentation on the comp cams website:
http://www.compcams.com/information/Products/Pushrods/

just in case anyone else is interested in this.

Is .025" preload on the hydraulic lifters correct? how could different lifter preloads affect performance?

The Blonde Weasel
San Diego, CA

gkull

So what did you come up with for pushrod length? It's been my experience that standard length are good till you start getting up to .500 - .520 lift with 1.6 i also always set my h-flat cams with .003 feeler gauge. I always thought that 1/4 turn or half turn preload was way to iffy. For pushrods I always use the the heavy wall chromemoly.

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Hey, I'm sorry about that whole OT thread. I'm glad to see that your a young guy with such a hot Vette. My daughter is turning 18 and she's into the hot rice cars and street racing. I'm also a IT person as a network engineer. Please stay with us on the c-3 forum. Look at my home page sometime I have a pretty hot 79. Although I made mine perform on lower octane. I like your profile e-mail address! LOL
Some times people get carried away and I'm sorry for the small things that I said. Okay? IM or e-mail me sometime. George