Mild 340 build runs hot

A/B Mopar said

I may be way off base here, but I fixed some overheating issues on a couple SB chevys by installing a spring in the lower radiator hose to prevent it from collapsing. On one of the engines, I could barely see the radiator hose collapsing, but it was and the spring fixed the issue. They all used to come with a spring, not anymore. Just a thought before you take it apart.

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The hose only collapses when you rev the engine up, creating the low pressure in the pump to suck it closed. Let off the gas. it opens NOW.
It was sheer luck I was looking at the hose as I revved the engine, the first time I experienced it.
Was a hearse that couldn't return down the hiway with the procession cuz it overheated at speed.
Lotta people scratched their heads before we got it.