The single overhead cam (SOHC) conversion head was Hosterman's first head for the new Model A engine. He probably wanted it to be a racing engine, but initial advertising that hit the streets in 1930 was directed at those who just wanted more power in their stocker.
Hosterman worked out the design and did testing for three years. He built additional speed and power potential into this 80 HP head right from the beginning. Design included dual intake ports (i.e., intake ports on both sides of the head). The passenger side could mount any Model A stock or accessory intake or exhaust manifold. A second special intake manifold could be mounted on top of the head just under the cam cover on the driver's side. Hal seemed to prefer Winfield carburetors.
Advertised benefits included:
All parts necessary for installation were to be furnished at advertised price. Average installation time was estimated at about 5 hrs. New head added about 25 lb. over stock.
Head casting material advertised to be of finest chrome nickel iron. Cam housing, water pump and intake manifold are cast aluminum, finished to high polish.
Combustion chamber is circular at bottom, tapering from both sides 30 degrees to top of chamber; compression ratio is between 6.5-7 to 1. Valves: 1-5/8” dia. Removable valve guides. Spark plugs located in center of combustion chamber; eliminates need for dual ignition.
Head is furnished with regular Ford-spec cam, unless racing-spec cam is requested. Chain-driven camshaft and valve mechanism are lubricated from Ford oil pump through a line taken off side of motor. Oil is drained back through head casting to Ford valve chamber.
Stock-spec SOHC head was introductory priced at $81; regular price given as $135. Had one-yr guarantee.
Racing head, with special cam: $150.
Magneto bracket, including water pump: $50.
Set of three steel timing gears: $20.
Dual carburetor manifold for stock cars, same as used on head: $15.