Milodon Chrysler Oil Filter Gasket Bulletin 21250 - Manual

Chrysler #21250 Filter Adapter Gasket Bulletin
June 1996
The Big Block Chrysler oiling systems with the filter in the stock location use the #21250 filter
adapter. The gasket used for this filter plate should be the “green” gasket. If you still have a gray
gasket, a new green gasket should replace it as soon as possible. It is available in the Oil System
Gasket & O-ring package Milodon #21590.
Baring in mind that Milodon oil systems have been in use for over 40 years and many of those
systems are still in use, there is a rare occurrence of failures with the early “gray” gasket. Any
occurrence however is unacceptable.
The green gasket has been supplied in all kits since 1996. Milodon oil systems have been in
production since 1965 so there were many gray gaskets supplied. These systems were used on
everything from street cars to the Hemi Pro Stockers of the 70’s without incident. While the
majority of applications worked fine, if the filter plate clamping force is not sufficient there is a
possibility the gray gasket could be pushed out by oil pressure. The green gasket contains kevlar
fibers and while oil can leak around it, the gasket itself has adequate internal strength not to
fracture and be pushed out of place.
The clamping force of the filter plate may be diminished by several factors.
1. The two filter plate bolts must be tight enough initially. Being countersunk bolts that are
torqued to 35 ft/lbs, they will then require a substantial effort to loosen them.
2. The bolt inside the filter cavity sits about 1/8” deeper that the outer bolt. If that threaded bolt
hole inside the filter cavity picks up any chips etc, the bolt could bottom in the hole before it
properly clamps the filter plate. While appearing tight it would allow a loose gasket and
subsequent leak.
3. In rare cases, the hole may have too little sealing area around it due to pump cover thickness
variations and hole placement. There should be a minimum of .130 sealing surface for the
gasket to seat on.