Just to correct the statement in the article linked above, that “earlier small block…. Chevy engines never had steam tubes”. At least one engine did. Specifically, the LT1 Gen2 SBC, used in 92-96 Corvettes and 93-97 F-Body’s (plus a few full size Chevies, Buicks, and Cadillacs) had a steam tube, venting air/steam from the back of each head, and returning it to the radiator.
The LT1 was the first SBC to use “reverse flow” cooling. Because Jack Evans (owner of Evans Coolant) filed suit against GM for stealing his idea for “reverse flow cooling”, GM was hesitant to use it again. But Evans lost the suit because GM sold the first car with an LT1 engine in 1991, a year before Evans filed for a patent on the concept. Evans had been trying to sell GM on the reverse flow concept since the late-1980’s. So GM was able to apply the concept to the Gen3 SBC (the LS1) and later versions.
Read Evans v. General Motors Corporation, 2001 Ct. Sup. 11813, see flags on bad law, and search Casetext’s comprehensive legal database
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You can see the LT1 steam tube in this photo (labeled as “steam pipe”):
