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.
I recall reading or hearing that Wayne Horning used the Winfileld head for the Model A engines as a guide for his head design for the Chevy six, starting the design work prior to World War 2. The open combustion chamber design and spark plug location are certainly not desirable for a high performance engine. It seems to need a lot of spark advance (more than 40 degrees total) and a rich mixture to run well. I'm about to install two wide-band O2 sensors to measure the AFR.
Panic: How is the downdraft angle defined?
