guys, I have no idea where the .010 spec came from, but I would never run them that tight. Dennis is right on the money with this one. 50 years ago we were all taught that ring end gap was crucial, if it was too large, the engine would burn oil, lose compression and the fellow who did the work would suffer all kinds of embarrassing physical maladies. Then, sometime in the early seventies, a ring company started testing some rings with 'preset' end gaps. First they were tested at a normal gap around .020 ( never have I seen anyone try an .010 gap ), and the results, of course, were normal. Then an .030 gap was tested, then .040 and .060, with the testers hiding under the table in case the engine ate so much oil it failed and went grenade. Nothing unusual happened. The dynos couldn't even see the difference. When tested with over.125 end gap, they could see some power loss on the dyno, just a couple of percent.
I am also remembering a customer who assembled his own engine ( Chevy LS ) we knew he was going to push hard, no nitous or boost, just hard use. We suggested extra gap. He chose to listen to someone else who told him stock specs were fine, and he went to the tighter side of stock. His engine failed on the dyno in less than fifeteen minutes. over 3K destroyed.
I wonder what he thought the tight gap was going to gain him ?
Go big here, it won't hurt anything. Going small is definately a risk. If you doubt, buy a set of 2M139 rings or similar and see what gap the factory gives you now,........you'll find .020 to .030 LSG