Inliners International Forums General Discussion Hi Performance general question on 12 port heads

It is 100 hp - if the engine has max mods and can pull high RPM.

There's nothing un-streetable about a 12 port, except that some of them are not quench and you have to watch the spark and mixture.
A 2 × 2 Weber 5200 etc. and a mild cam should be a calm as a stock V8.

The current 12 ports for the 250/292 are highly developed, those for the 235/261 were already obsolete when produced (read Huntington). Vertical valves, open chambers, and low downdraft angles are inferior to the better modern L6 engines such as the Slant 6, AMC 258, Ford 300. They're just better than the original heads.