I hope you all had a Merry Christmas. Here's one for you all. The 28 Chev. Repair Manual describes how to fit pistons. It says free on .001" and bind on .002". I just pulled the head from my old 28 engine and I can peer down the cylinder walls and see the top ring of each piston. Looks as though the clearance is more like .020". I just put 500 miles on this engine in a single run without any problems. What is the tolerance on this application? What are the side effects of incorrect piston fit? This engine should have busted apart according to the book.

-Rusty

Rusty,
I will keep response brief.
Basically with the old full size piston skirts severe damage does not occur until tolerance is fairly large. Don't know the exact answer. Before failure you will get piston to wall knock particularly at low rpm (my '31 is 0.005-0.010"). I have put 1800 miles on this "temporary" engine. With more wear you will get scoring of the cyliner walls and piston skirts. This is when you need to seriously consider making repairs. Next you will begin to cause considerable wear and break rings etc. In summary these engines will take a lot of wear before they fail.

Thanks Chip,
Without actually removing a piston, I am told that the ring land of the piston has a smaller diameter than the skirt. This might account for the loose appearance. I wont know for sure until I pull it out. Thanks