Rear Lip Seal Conversion for A-series engine


Rear Lip Seal Conversion

This conversion kit can be used in conjuction with a 5 speed conversion or with the factory back plate and original 4 speed transmission.
1275cc seal kit components
1275 Seal Kit   Precision CNC made to very tight tolerances. Seal halves will fit together perfectly everytime.

* A Word about Seal Kits

The original BMC rear engine seal design for in-line A-series engines is what is called a "scroll seal" (Archimedes scroll pump). Simply explained, there is a helical groove at the rear of the crankshaft that will draw oil back towards the internal engine while the crankshaft spins. A vertical flange called a slinger, acts as both a barrier and a means to divert oil from it's natural path as it tries to exit the rear main.



The animation above illustrates the priciple of an Archimedes spiral scroll. The action works as a simple pump.
Seal Kit Installed  
Seal Kit installed with 5 speed kit

In Theory

In order for this system to work properly, it is of primary importance that the engine be in decent operating condition, properly vented, and be accompanied by vacuum pressure and a PCV. Often, if these conditions are met, the original design is sufficient. However, sometimes these engines aren't built with the correct tolerances or are worn beyond acceptable tolerances to make this system work 100% of the time. Hence, a rear lip seal kit has been designed to help out as a substitute. Even with the lip seal, it is still important that that the vent and vacuum conditions be observed. Unfortunately however, one of the weaknesses in the lip seal retrofit design has been, the replacement half moon seal that is supplied with the kit. Because it does not follow the original design concept to take advantage of the original scroll seal design desribed above, it instead relies entirely on the lip seal to retain the oil.

The Big Difference

My seal kit is different. Instead of depending entirely on the lip seal, it incorporates a half moon seal that takes advantage of the original scroll seal design and has the added benefit of the lip seal as a back up. This design incorporates several improvements and is not available elsewhere.




Contact me for details.