Ask the average performance enthusiast about the Ford's modular family engines and you'll usually hear a barrage of preconceived and misguided notions: The engines are too small. Those things don't make torque. You need a blower to make power with one of those. The bore is too small for real horsepower. Ford blew it when it phased out the good old Windsor small-blocks. The opinions go on and on, but the reality is that the mod motor, introduced in 1991, has been one of the most successful and innovative series of V-8 engines in production history.

Notable for its single or dual overhead cam layout, the mod has been produced in two-valve, three-valve, and four-valve variations, with iron and aluminum blocks, in a staggering range of displacement and horsepower output. It is safe to say that the mod has been offered in a broader range of permutations than any engine in history. There is little debating the mod's success as a production engine. Still, outside of modifying late-model vehicles, suspicion of the mod seems to linger in the hot rodding world.

When we revised the rules for the 2013 AMSOIL Engine Masters Challenge, one of the changes from previous competitions was to remove the prohibition on four-valve engines. We wondered how many would take note of this revision and take up the mod as the basis for a completion build. From a classic engineering standpoint, the advantage of a four-valve layout has been documented since the early part of the 20th century. Still, we had to wonder how common misconceptions might influence the acceptance of the mod engine in our competition. After all, this was a contest of normally aspirated power—one in which low-end torque is a major contributor to score—and finally, there was the hurdle of a 400ci minimum displacement. This is not the normal venue of the mod Ford.

Jon Kaase of Jon Kaase Racing is an engine builder known for innovative thinking and exceptional engine-building talent. Kaase saw an opportunity in the four-valve Ford. "I started thinking about it right after the rules were announced last year at the press conference at the PRI show. It just looked like if you could make it big enough, it would be an interesting project. I thought it could be very good, but I wasn't sure, since I didn't know that much about them or what parts existed. I started to do some research because I didn't have any history with that engine whatsoever."

Job one was to explore the possibility of increasing the displacement to meet the 400ci requirement. Kaase explains, "I really didn't know how much stroke you could put into one, since nobody really had taken these engines to this kind of displacement. I had to see if big displacement was physically possible, but in the end it turned out to be pretty easy."

Kaase began by looking at block selection, considering both the iron and aluminum blocks available. Determining the iron blocks to be more limited in bore size, Kaase went with an aluminum 5.4 production block as the basis. He elaborated on the block, "The aluminum block has Siamese cylinders and does not come with a sleeve in it. It comes with a thin plasma coating as the liner in the cylinders. I bored it out, designed some thin 0.050-inch wall sleeves for it, and ended up with a bore size of 3.720 inches." Kaase had a custom billet crankshaft cut by Bryant, using the OEM journal diameters and a 4.700-inch stroke. Filling the bores are custom Diamond pistons built from a model made by Kaase for this application, with Eagle 6.658-inch rods connecting the internals. The combination yielded a displacement of 409 ci, making it the largest known engine of its type ever built.

Exotic Top End

Clearly, the defining component of the engine is the four-valve DOHC cylinder head arrangement. Ford had several variations of these four-valve heads, with these being the Ford GT–style castings. Kaase actually acquired this set from Roush Yates as takeoffs from a Daytona Prototype endurance-racing engine. The heads were already CNC ported, and Kaase actually acquired two sets, giving him a set of heads to experiment with. As he tells us, "I worked on one of the sets, putting a little bit bigger intake valve in it. That is the set of heads I ended up running, but I really didn't see much improvement. To be honest, I did hardly any headwork, almost nothing. I did put the bigger valves in, but the other heads made every bit as much power."

The heads and cams were essentially a team, and optimizing the combination required unique considerations with the DOHC arrangement. Unlike a conventional pushrod engine, the DOHC engine opens the door for a wide range of variables and adjustments, with separate intake and exhaust cams allowing experimentation on centerline angle individually. Kaase described some of the theory and testing: "With all the valve area they have, at about half-lift there is a lot of valve opening area, so these engines will run about 20 degrees less camshaft. If you can run a lot less camshaft, it would seem to reason that it would make a lot more torque down low. With the very long stroke and the short camshaft, I figured it would be very good down low if it had the right manifold. Really, these factors influenced my decision to try the four-valve in the competition."