Interesting comments! I've been building "performance-enhanced" engines for over 40 years, starting back in high school with a flathead Ford V-8 that used various leftover parts from the family dirt tracker. Since then, I've run competition sports cars, a few (thankfully!) drag race engines, street machines, tractor pull engines, and a couple of hotrod boats. 1/4-mile dirt tracks are still my favorite, however. Nothing beats the sound of a dirt tracker running on alcohol with a gear-driven roller cam, and wide open exhausts. Some racing associations outlaw the roller cams, so we have to run flat tappets with triple valve springs andc extreme seat pressures to handle the RPM when a driver breaks the tires loose to power through a turn. I distinctly remember our driver's comment back in the mid-50's about RPM after a gear change one night- - - -"Well, hoss,- - - -it's runnin' 6,000 down the straightaway, and 6,200 in the turn!" He was talking about a 300 cubic inch Ford flathead with a 4 1/8" stroke, and 3 main bearings!
Cam break-in is very critical on those engines. I use a set of stock valve springs for startup, and run the engine at 2,500 RPM for at least 20 minutes before pulling the heads and installing the racing springs. I've seen too many round-lobe camshafts to do it any other way! After the initial break-in, it's pretty uncommon to see a worn-out cam, even on a full-house race engine.
Jerry
