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Four Cylinder Flathead Max Herman

Four Cylinder Flathead - Big 'Banger Theory

200-Plus Horsepower From A Four-Banger Flattie!
October, 2009
By Tim Bernsau
Four Cylinder Flathead Engine
H&H Flatheads built this Gemsa-inspired... 
   
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Four Cylinder Flathead Engine
H&H Flatheads built this Gemsa-inspired Donovan block four-banger with a chain-driven single-overhead cam conversion, following the way Joe Gemsa did it. They used lots of original parts and lots of fabricated parts too. The engine was delivered to Roy Brizio Street Rods where it was dropped into a project hot rod owned by John Mumford.
Even before Henry's breakthrough V-8s, and decades before the introduction of the Chevy small-block, these were the prevalent powerplants. Even after the Flathead V-8 was introduced in 1932, four-bangers retained their popularity. One reason is the fact that a lot of development work had already been done, and a lot of speed equipment had already been created to make the four-bangers fast. A four-cylinder with an overhead conversion could be built to make cubic inches and horsepower that the V-8s had a hard time matching.

Four Cylinder Flathead Cam Saddle
The cam saddle for this engine... 
   
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Four Cylinder Flathead Cam Saddle
The cam saddle for this engine was based on Joe Gemsa's design. The original Gemsa cast parts are shown next to the custom billet parts, which were modified by H&H.
The four-banger knowledge that Gemsa passed on to Max Sr. has been passed on to Max Jr., who is the four-banger performance specialist at H&H. We were there when they put together this SOHC 'banger.

Four Cylinder Flathead Cam Four Cylinder Flathead Camshaft
Four Cylinder Flathead Head
The head is from an original... 
   
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Four Cylinder Flathead Head
The head is from an original Gemsa casting and was one of his last. His cylinder head design and his camshaft design were all incredibly advanced, Max Sr. told us.
Four Cylinder Flathead Tappet
These tappets are used between... 
   
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Four Cylinder Flathead Tappet
These tappets are used between the cam lobes and the valves. The case hardened steel housing holds a removable steel wafer that pushes down on the valve stem and spring to open the valve. Changing the thickness of the wafer adjusts cam lash and sets the valve clearance. Valve lengths are never precisely equal, but even a difference of 0.001 inch is a problem at the cam. Using various puck thicknesses takes up those differences.
Four Cylinder Flathead Stamping
Joe Gemsa put his name on... 
   
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Four Cylinder Flathead Stamping
Joe Gemsa put his name on everything. Every head he ever built was numbered and dated. This was one of his last.
Four Cylinder Flathead Head Stamping
The stampings read: NO. 83... 
   
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Four Cylinder Flathead Head Stamping
The stampings read: NO. 83 1986, EXPERIMENTAL HEAD and TEST OK, BUILT BY JOE GEMSA, EL MONTE, CAL.

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