On a hard pull at high RPM on the dyno, I've seen original equipment rams' horn manifolds glow cherry red all the way from the heads to the exhausat pipe flanges. Headers get so translucent you can see the flames dancing around inside the tubing. I wonder what those Chinese repops would look like during a full throttle run up sometning like the Grapevine hill in California? That's 6 miles of 6% grade. or at least it used to be when I was trucking there back in the late 1970's.

Big block Chevy motorhome engines had a bad habit of cracking exhaust manifolds (and heads) from the stress of pulling those big shoeboxes uphill. I've done some road testing with the engine cover off at times, and the orange glow from the exhausts is pretty impressive on a long upgrade.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!