I pulled apart the rods and pistons in my 400 small block to add different pistons. One combo was pulled and took both hands to rock piston back and forth on the pin? There is some black gunk around the pin I am assuming it is cooked oil. It has the consistency of silicon sealant. All the others rocked freely on themselves like they should.
I also noticed with the pistons all upside down that the width of the piston where the pin and rod ride varies huge on one. The odd one measured 1.5" all the others measured 1.25". Is this normal?
One other question I noticed on almost all the bearings pulled there are very small grooves, nothing like the other post of bearing failure. Should these be scotch free and perfect looking? The motor was just started at the machine shop and not broke in at all. Also what should the rod bearing surfaces look like? Should they be ruff so that the bearing has something to adhere to? Thanks

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I'm assuming those bearing havent been ran very long? It is not normal.

 

Josh,

1. The piston pins should move freely.

2. The pin bosses should all be the same size, especially if the rotating unit is supposedly balanced.

3. The bores for the bearing shells shoudl have a machined finish, but not polished.

Of coursem the shells should be clean and dry when installed. The finish of a new bearing sheel should be a dull tin with no real polish or mirror finish. The small grooves don't sound like a good thing, and could be a sign that the engine case was not thoroughly cleaned of all debris before assembly, and the particles may have scuffed the bearing shells on startup.

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Later,
Vader
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