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
