New one-piece seal conceived for use on Ford 429-460 big-blocks; Boss Nine; and P51 engines

• ∇ Simple assembly; reliable service
• ∇ See installation sequence below

Without wishing to diminish the performance of any current rear main seal for the Ford 385-series engines, Jon Kaase wanted more.

“We had to go out of our way to find it,” he says. “In fact, we had to go out of the country—to England—to get the quality we were searching for.” Using the same manufacturing source as the Sprint Cup teams and following several years of testing, the seal makers produced the tooling, the prototype seals and now the production items exclusively for Kaase.

This new seal is a one-piece device that replaces the conventional two-piece arrangement. On its face there is a dot—a small indentation—that represents the exact place to cut the seal with a razor blade for installation.

Once cut, the seal can be wrapped around the crank and a daub of silicone sealer placed in the joint. Before lowering the crank into the crankcase, apply a light film of silicone to the outer perimeter surface of the seal and rotate the joint such that it is positioned in the main cap.

There are numerous causes for rear main seals that leak: insufficient lubrication at the sealing lip edge, shaft roughness, lip hardening, lip softening and so on. But what offends the racers and hot rodders most is the indignity of having to do the job twice, which is often a day wasted if the oil pan cannot be removed without raising the engine half-way out of the engine bay.

To this end Jon Kaase’s new rear main seal for 385-series big-block Fords is aimed at sealing it right first time.

When legendary AMSOIL Engine Masters participant Jon Kaase considered the new Vintage V8 Class for the 2015 Challenge, he contemplated engine possibilities with the cold pragmatism of a serious competitor. One of the key requirements from Kaase’s perspective was the availability of an aluminum cylinder head. As Kaase explains, “An aluminum head allows almost unlimited modifications, and in an unlimited class like this year’s Vintage category, we wanted a head that can be machined and welded or modified.” Topping the Mummert heads is a custom adapter mating the heads to a tall Edelbrock small-block Chevy tunnel ram. The bottom end was built with a Bryant billet crank, Carrillo rods, and custom Diamond pistons. The result is a 400ci engine putting the squeeze on the mix at a 13.9:1 ratio. To work with the mushroom-tappet arrangement of the Ford Y-block, custom lifters were manufactured by Trend, with a Comp Cams billet flat tappet orchestrating the movement. Kaase custom-fabbed a long set of tri-Y headers and installed an MSD ignition system to light it off.

So what is the effect of all of these mods on this ancient Ford? How about numbers that would leave any builder of the latest hardware slack-jawed at the results. Torque started off strong at 526 lb-ft at the 3,000 rpm bottom of the test range, and twist only ramped up from there. Peak torque recorded measured 596 lb-ft at 4,600 rpm. On the power side, Kaase didn’t disappoint, with peak output showing 584 hp at just 5,500 rpm. That was plenty of power and torque over the rpm range to net a class-topping score.