You want to talk about traditional hot rods? Let's talk about four-bangers.
H&H Flatheads built this Gemsa-inspired...
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.
That changed eventually, but a few rodders never lost their devotion to 'bangers. Joe Gemsa was one of them. Gemsa was a champion Sprint car driver in the '40s and '50s, built and raced cars in NASCAR, and was one of the best at pulling performance out of four-bangers with his single- and dual-overhead cam conversions. Joe passed away in 1995 and four-bangers have become something of a niche in the hobby, but they still have a high cool factor and a high potential for making power.
If Joe Gemsa was "King of the Four-Bangers," then the Hermans at H&H Flatheads are next in line of succession. Max Herman Sr. opened H&H in 1972. Since then, his sons Max Jr. and Mike have joined him, continuing to build flatheads and flathead parts for extracting maximum performance.
And guess who taught Max Sr. how to build engines? "Joe taught me how to build these four-bangers to make them go fast," he says. "Everything he built was about going fast. There was nothing slow about anything he ever fired up."
Gemsa built engines and parts in a 20-foot refrigerator car behind his house in El Monte, California. "At the end of the refrigerator car he had a small lathe," Max Sr. says. "He made everything on that-pistons, rods, cranks-everything. He had a drill press, his work table, a tiny mill, and a welder. That was his entire shop. His mill work was incredible, and he could weld cardboard to tinfoil. It was amazing to watch him."
The cam saddle for this engine...
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.
The whole thing starts with a Donovan aluminum block with five main bearings. Internals include splayed main caps, a billet steel crank, forged steel rods, Arias custom pistons, Total Seal rings, and hardened steel sleeves. "It will probably make over 200 hp-and it'll be capable of driving every day if you want," Max Sr. says.
The billet cam tower was based on originals cast by Gemsa. "This isn't just a standard-style overhead," Max Sr. says. "It's running an overhead cam chain drive, which is pretty old school. The old Offys and DOHC HALs and others were chain driven. That's one of the ways they made horsepower back then." At H&H, it's one of the ways they make horsepower now.
The head is from an original...
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.
These tappets are used between...
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.
Joe Gemsa put his name on...
Joe Gemsa put his name on everything. Every head he ever built was numbered and dated. This was one of his last.
The stampings read: NO. 83...
The stampings read: NO. 83 1986, EXPERIMENTAL HEAD and TEST OK, BUILT BY JOE GEMSA, EL MONTE, CAL.
Standout elements of this...
Standout elements of this engine are the chain drive and the fabricated front cover. The chain runs inside the cover from the cam in the block up to a tensioner and then to the overhead cam.
The chain runs inside the...
The chain runs inside the cover from the cam in the block up to a tensioner and then to the overhead cam. Chain length has to be accurate and involves determining the diameter of all gears. Installation is tricky, time consuming, and fun to watch other people do.
H&H made this adjustable and...
H&H made this adjustable and accessible chain tensioner, consisting of a sprocket gear on an eccentric hub. All you have to do to adjust tension is rotate the assembly-easy since the cover plate features slotted holes. It's not a Joe Gemsa design, but a variation and improvement on Gemsa's tensioner.
When the helical gears are...
When the helical gears are rotating fast, the cam wants to move forward. Henry Ford used a spring and plunger device to push back on the cam. H&H's solution is a small aluminum threaded plunger for the lower drive gear with a trunnion bearing at the hub. The plunger provides resistance to cam thrust, and is held in place by an outer cap built by Max Sr. The nut on the outside of the cap adjusts tension. Turn the nut until you feel resistance, back it off a touch, and tighten down the cap with Allen bolts. Trick piece.
Gemsa cast his 'banger heads...
Gemsa cast his 'banger heads with a large opening at the back. "This was their version of the freeze plug," Max Jr. explained. "Instead of running freeze plugs like you see in heads today, he cast them wide open. The open end was sealed up with a plate." You can see the plate at the upper right in this photo. H&H set up the cooling system to run water into the engine from a port on the driver side of the block, where the lower neck is located. A braided line delivers cool water into the back of the head.
Gemsa's heads were designed...
Gemsa's heads were designed to run at high compression, somewhere between 9.5:1 and 10.5:1. H&H uses these Arias pistons with unique domed tops to bring up the compression. This four-banger runs in the neighborhood of 10.2:1 or 10.25:1 compression.
This Wico Series C mag is...
This Wico Series C mag is an original piece from a swap meet. It drives off the cam gear, on the same system as the crank gear; 2:1 reduction gearing in the magneto keeps it spinning at half crank speed (equal to cam rotation). The Wico is infinitely adjustable; Max Jr. set it up for about 24 to 26 degrees advanced timing. Although, much higher than that and he's risking detonation, he warned. There is hardly any room between the Wico and the oil filter and pump, so the pump was repositioned, the delivery hole plugged, and the line rerouted to the other side of the assembly.
A billet adapter allows the...
A billet adapter allows the use of a cast '32-36 style water pump. The pump is a brand-new casting, mounted off the front of the cylinder head, fabricated by H&H.
These forged port exhaust...
These forged port exhaust headers just happened to be in the shop, waiting for the right application. They came off of a 1,000hp dragster motor that had ended up there. Max Sr. cut the tubing off the race car, gas welded them up, and had them chromed. At approximately 2 1/2 inches in diameter, they are actually larger than the exhaust ports.
A pair of Stromberg 97s atop...
A pair of Stromberg 97s atop a Gemsa intake manifold will handle the induction duties.
Max Herman Jr. and Max Herman...
Max Herman Jr. and Max Herman Sr. from H&H Flatheads, proud of this four-banger, built following the way Joe Gemsa did it. He' be proud too.