I'm with Alvin and others on this one, myth busted. Aircraft engines aside. My Dad ran dirt track cars in the late 70's and like everyone else ran with only headers...no exhaust. Depending on how we ran, if we lasted late in the season, we were racing in late October and I remember sitting in the stands freezing my butt off. Never an issue. I'm thinking the myth got started when someone was cleaning up the shop with compressed air and shot a blast up a hot manifold and maybe bent a valve. Unless the Professor comes up with some good Physics/thermodynamics here, one less thing to worry about. Keep calm on bolt on !


Allen
Yeah, well, that's just like, you know , your opinion, man - The Dude

1948 Chevy 3600 - goal Original restoration, Current Stage 1 - Disassembly and getting body in primer
1954 GMC 3100 goal Hot Rod, Current Stage 1 - Get body in primer
1931 Ford Model A 5 window Coupe - Old Skool Hot Rod
1945 Ford 2N Tractor - Runs great
1964 Ford 2000 Tractor - Use it every week
1974 Stingray Corvette