1937-1938 EL Knucklehead Bare Cylinder Head Set

1937-1938 EL bare Knucklehead head set features OEM production numbers, mc hallmark, small intake port, primer black plugs, manifold nipples and are painted with black heat paint.
Exact for 1937 only, but can be used on 1937-1939 61" EL models. Either type of valve spring cover can be installed, either cup type of full cover and top set. Accepts "Baby Butt" intake manifold, springs, valves, collars, spring cups and top tins included and assembled. *NOTE: Valve seats are installed but not cut. Uses 1-3/8" large hex 18mm plugs. *NOTE: Heads include feature detailed casting hallmarks, as original, black painted. *NOTE: Accepts large 1-3/8" hex Doering #3 spark plug set. Material of valve seats features a better hardenability and heat resistance than 1.2713. Material is tough with high compressive strength and high tempering resistance. Hardness equals 370-415 HB. Tensile strength equals 1250-1400 N/mn2. Condition is tempered.