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Old 09-05-2019, 11:17 PM   #1
FasNuf
 
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Drives: 2014 Camaro ZL1
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Comp Cams Pushrod Measuring Tool

I bought this tool and it's supposed to be able to measure from 6.800"-7.800"

In the closed position I get 6.812" I verified this with a machinist at work as well using a different method to measure.

Is the end to end method of measuring this wrong?

Last edited by FasNuf; 09-06-2019 at 07:39 AM. Reason: update
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Old 09-06-2019, 08:03 AM   #2
FasNuf
 
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UPDATE:

So I decided to measure the pushrods going into the engine I'm working on and determined that they're over length too by .014" So 7.414" long. So I guess it must be added to length because of wear right at the tip that doesnt survive break-in.
So doing the math with the tool, if I add the errors to the tool and the pushrods, the preload comes out the same as if I just use their advertised lengths anyway.

10.25 turns @.050" = .5125"
6.800 tool length + .5125" = 7.3245 zero lash value
7.400 pushrods - 7.3245 zero lash = .0875 lifter preload.

the machinist at work had a much better caliper than I did and still showed the tool and pushrod to be .012" longer than advertised ,but this was at the extreme tips.
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Old 09-10-2019, 03:10 PM   #3
Russell James


 
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The Comp tool is accurate.

Ball end PRs are not measured tip to tip. It is measured at a mid point in the ball end radius. Basically, half the rounded tip is not included in the PR stated length.

Follow the directions that came with the Comp tool. They are very helpful.

Katech also has a great video on YouTube for selecting LS PRs. I think they shoot for .070" plunger depth. You balance getting close to the ideal depth while maintaining the correct valve stem sweep.
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