Long story short, I had my main and rod journals polished because they had some scratches that I wanted to clean up. When I plastigauged them the clearance measured at about .002 which I think is a bit much. What is the recommended maximum clearance and what is the best way to accurately measure it? I have a set of micrometer and telescoping rods. Is there a better/easier/more accurate method?

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

here is an article on checking clearances using a micrometer and a dial bore gauge.

https://blog.k1technologies.com/how-to- ... clearances

What the article mentions is basically how I verify rod and crank clearances. But then I have a dial bore gauge around to also check cylinder bores, can't do that with plastic gauge.
If I was only building one motor I would go with what the machine shop provides for pin and crank clearances, but then use plastic gauge to verify.

Plastic gauge is accurate for most builds, probably to almost three decimal places, to get resolution to three decimals and beyond, I believe you need hard gauging.
I would also want plastic gauge that is somewhat fresh, I would not trust it if you did not know how long it was setting around.

Concerning the clearances that you mentioned,, .002 when you get to making hard decisions that is why more resolution can be helpful. Is that clearance really .0020 or is it .0027 or maybe .0019 ?

If you don't want to invest in a dial bore gauge consider taking the crank and rods to a good shop and have them measure them.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

Doug's book says out to .0025 is ok. On an old used engine rering job I would even go as far as .003. More than that and oil pressure at idle may start to become an issue.

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63 Plymouth Valiant Wagon

I always shoot for around 0.0020" or maybe a bit more on my performance engines. I would not worry about it a bit.

Lou

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