identifing piston size ??

[TnA]

I picked up a set of pistons recently and have no idea of the size reading on the top. the number is 634 and thats it. can any one help me out here. thanks Bruce

 

[Flathead]

Measure them?

 

[MikeK]

Yep, measure. A few years ago I pulled a set of pistons marked .050 on the tops. The bores were only 20 thou over. What??? Turns out that number was centimeters. Foreign import pistons. 0.050 cm = 0.0197 inches.

 

[TnA]

these pistons measured across the top at 3.902. does this give me a .020 or a .030. over? thanks for the help.

 

[MikeK]

these pistons measured across the top at 3.902. does this give me a .020 or a .030. over? thanks for the help.

That gives you nothing. Most pistons have a reduced diameter in the ring area. You need to measure on the skirt just below the pin, 90 degrees to it. If you then turn the piston 90 and measure again, you may get a different reading. Many pistons are cam ground or machined (Oval) to keep them from knocking.

Forget the piston. Use a bore gauge to see where you are at.

 

[1931 flamingo]

MikeK: Picture Magic ! ! ! ! Neat.
Paul in CT

 

[BILL WILLIAMSON]

MikeK: Picture Magic ! ! ! ! Neat.
Paul in CT

Paul,
Betcha' MikeK could make Vermin jump offen' the 4 Harbor Freight jack stands!!! Try it Mike, I got the computer plugged into Vermin's U.S.B. port! Bill W.