Originally Posted by poncho62
Old wives tale
Of course it is.
I watch oval track races at the Taft track (Orlando Raceway) back in the '60s that had many low-buck race cars that used absolutely NO exhaust manifolds at all- nothing, zip, zilch, nada.
These guys were not front runners, mind you- they were in it for the fun of it. But these same guys- running the same engines- were there week in week out, for the entire season, and there's no reason to think these same engines weren't run for several seasons, and know what? Nary a warped valve to be seen.