I had planned on reusing the pistons I pulled from my '51 Ford flathead engine, they are in very good shape, even still have the logo and checkering on the skirts. I measured them today, and found there is nine thousands difference in the measurement from across the sides where the pin is, and at 90 degrees to the pin. I would expect to see the smaller measurement at the latter position, but it's at on the pin side. Is this normal, and are the pistons still usable? I measured 4 pistons, and they are all the same.
Thats the way pistons are made. See the "Cam Ground Pistons" thread. What may be the really worn part of your piston is the ring groove. If the ring can't seal against it, it can't seal. You did remove the ridge before removimg the pistons, didn't you?
The "checkering" you noted is knurling added the last time the engine was re-rung. It tells you to check the wear in the bores. Knurling was done to save the cost of boring & new pistons.
There was only a slight ridge, the pistons easily slid over it. The ring grooves are square with no sign of wear and the rings fit nicely with no slop. I don't think there were many miles on this engine since it's last rebuild.
No, I don't believe the pistons have been knurlled. The checkered pattern does not go around the piston, it's just a rectangle above and below the logo that is stamped in the skirt of the piston.
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