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-   -   plastigage position clarification (http://forums.pelicanparts.com/911-engine-rebuilding-forum/915171-plastigage-position-clarification.html)

bigred23 05-20-2016 11:24 PM

plastigage position clarification
 
I preface this question knowing the various opinions regarding the usefulness of plastigage....with that-

In Wayne's engine rebuild book, p. 120, he writes:

"Plastigage should be used at the sides of the rods, not in the middle. The rods stretch when under load, and you want to measure the clearances at the sides."

If I'm reading this right, plastigage should be positioned such that it is near the mating surface of the cap and rod? Based on previous related posts and pictures, it appears most are putting the plastigage in the 'middle'. Thoughts? Has anybody noticed differences in bearing clearances depending on position? Reading too much into this?

Gordo2 05-21-2016 12:25 AM

Plastigage Position
 
I recall scratching my head at the same for a moment - then moved on placing the plastigage toward the center...

http://forums.pelicanparts.com/911-engine-rebuilding-forum/788681-checking-connecting-rod-bearing-clearances-plastigage.html

I think my thought process was - this is just a clearance confirmation, not a precise measurement, don't over think it.

Good luck,

Gordo

prschmn 05-21-2016 03:06 AM

I'm afraid Waynes description isn't quite right here. Rods mainly "stretch" when under tension-IE
under decel. It's for that reason that many bearing manufacturers offer more than one amount of
built in eccentricity to compensate and prevent pinching at the sides when in tension.
Just put the Plasitgauge in the middle-you'll be fine.


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