I have a 1997 Indy 500 Classic Touring that melted down twice three years ago due to a bad check valve in the oil line. This was at 600 miles, had it bored out .020+ oversized and was running fine for the last 475 miles then locked up doing 55+mph. It never came to a stop but kept on going without dying. Luckily this was within a 1/4 mile from home. Pulled the plugs and they were the same on both sides, nice and brown. Looked at the top of the pistons and the mag side was like brand new. Clutch side was pitted slightly the size of a dime right in the center. Both pistons were clean as can be, just like new. Motor turns over just fine and idles normally. What would cause this to happen? I do know that I ran about a tank of 87 octane without thinking about the oxygenated thing. Also, as far as I know the main jets are still stock. Please help me out here as I would hate to do anything that would further my problem. Thanks!