Kaase abandons traditional two-piece big-block rear main seal

Kaase abandons traditional two-piece big-block rear main seal
  • 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

Winder, Georgia: 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.

For further information contact:

Jon Kaase Racing Engines, Inc.
735 West Winder Ind. Parkway,
Winder, GA 30680,
Telephone (770) 307-0241 or email: JonKaaseRacing@gmail.com




Cut Seal







  1. Looking to purchase one piece rear main seal for 1973 ford 460

  2. Can you install these seals with the engine in the truck? My new 468 rear main is leaking I used the Felpro 2-piece seal.

    • Jason,

      While you may be able to snake the rear seal in with the engine assembled, we do not recommend it. Though we have successfully performed the procedure, others have failed, so we do not endorse it.

  3. Will this work on Olds 400-455s also?

    • Frank,

      While we do not sell them for Buick or Olds engines, numerous customers have purchased them for this purpose. Nonetheless, as we have not designed the seal for them or tested them on these engines, we cannot say for certain if it would work satisfactorily or not.

  4. Will this work on the FE Fords? If not are there plans to make them for FEs? Thanks.

    • Frank,

      No, the FE engines use a different size rear main seal than the 385-series engine. You can purchase this style of seal for an FE through Roush.


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