A race engine that cost somewhere in the neighborhood of $12K to build was usually good for about half a racing season on a 1/2 mile track- - - -that's way less than 1,000 miles of repeated full throttle operation followed by a quick chop of the throttle to get around the turns. Accelerating from a minimum of 3K RPM in the turns to 7500-8K at the end of a straightaway maybe 800 feet long, repeatedly, has a tendency to wear stuff out, even if the engine doesn't hand grenade itself. Dirt track cars on a 1/4 mile course were even shorter-lived because of all the dust and dirt they ate. Those engines had wider clearances when brand new than a 100K mile street engine! It has to be that way to keep them from tightening up and seizing from piston expansion and too-close bearing clearances! A race engine with mufflers on it sounds like there are a bunch of little guys with sledgehammers inside, trying to get out!
Jerry
10-12 thousand was about what I spent on drag race engines at the level I was racing at. You got a lot more out of your engines than I did. 200 runs was it, about 50 miles of full throttle. Add in the burnouts and maybe 100 miles. The engines were still quite strong at that point, the issue was the manufactures recommendation of tossing the aluminum rods at 200 runs.
