Got my freshened 454's running and did a high speed run that melted/blew out the black rubber hose from my EMI thunder risers to the 3" offset that attaches to the tips. I don't want to take a chance on blowing out more hose. Is the best thing to do is just pipe with stainless tubing from the riser to the offset and what's the best couplers for making the connection?

Why did it get so hot ?

Glad you asked, because I questioned it also. I have twin engines the center most exhaust hoses burned at the top. I can only think that hoses might not have been centered on risers....however the outer most hose did fine. Opinions welcomed.

Doesn't sound like there was any water going thru it.

I would check impellers just to make sure you dont cook new engines

For sure, you can always get TriDent hose also works great and comes in colors. Super easy to get on and off and has a little better look.

Really puzzling why two center most exhaust both burned. Could it be because exhaust manifolds are so close (2-3") and it gets hotter than outside manifolds? It still ought to be cool. I'm open to suggestions. Does the new cams, rocker arms increase exhaust temp? I saw 40 lbs of water pressure at 70+. at idle tho about 10psi and my sea strains weren't to the top but were swirling about 3/4 full. Any opinions welcomed.

That's a lot of pressure, could there be some kind of blockage in those manifolds or risers . Did you notice consistant water coming out of all the tailpipes.

Sounds like you are running a bit lean, which if too lean, will be hot enough to melt the hose.

After you replace the hose, make another run and check the plugs.

Are the hoses a straight shot to the tips? Any bend in the rubber hose will cause the exhaust to impact that area and really heat it up.
That is a ton of water pressure. Remember that pressure is just a measure of restriction. Just because you have a ton of pressure doesn't mean you have the volume to cool the engine. You need a happy medium of pressure and volume. I would have to good look at the entire cooling system to be sure there are no obstructions. Unless you have an MLS head gasket, you take a chance of lifting the gasket with 40 psi of pressure.
As mentioned, the Trident silicone hose is really good stuff that will handle about 100 deg more than the rubber hose. It is also pretty pricey.
You asked about more temp with new engine parts. If you are making more power than before, then more than likely you are making more heat. However, there is no reason that the rubber hose shouldn't hold up as long as there are no bends or turns in the hose.
Eddie