Jump to content

'38 Special Rear Main Seal


Recommended Posts

Over the years I have probably tried three times to improve on the fit of the cork gaskets at the rear main bearing cap. (they seal between the cap and the block - the 320 engine also uses a packing, but the 248 does not) It seems that a cork cut generously will not assemble, and backing off just a bit gives me a significant leak. Is there another material or design available?

Link to comment
Share on other sites

I had the same Problem with my OEM Engine.

Buick start with rear Seal in '39 !! Two Years ago I had ordered the Sealkit # 3764 from Best Gasket and wondering why it's doesn't match in my '38 Engine.

The Reason :


Vintage Automotive Gaskets - Head Gaskets and Rear Main Seal Gaskets - Best Gasket.......[518]

The Engine will only be Oil tight because of the Backrunning worm in the Crank ,the centrifuge Sheet on the Crank and Air overpressure in the "airtight" Clutch housing.

My hoped up Engine (with a many milled Head ) never was thight on this Part . That was also a Reason to look for a newer Engine,in my case "sadly"a 263.

But the two Rubberseals and the brads are will work fine. (look at the Pic from BG )

I had wrote a E_Mail to Best Gasket,but they never answered or change the Date on theyr Package, thats sad ..

Edited by jenz38 (see edit history)
Link to comment
Share on other sites

Vielen dank, Jenz.

I always wondered how you keep up with European traffic with the '38 Special. A later engine certainly helps, along with the milled head. Are you still running the 4.44:1 final drive ratio? With more horsepower you could tolerate a better ratio, but it's a big job!

Regarding the seal - what you said makes sense. My gasket kit also contained a rope seal for the later years. The '38 shop manual says that the bigger series engine used this seal, but the 248 in the Special does not. They rely on the design features you mention.

Do you think it is possible to install that rear bearing backwards (bottom half in the top, and top in the bottom). Would that make the spiral work the wrong way? I don't recall if this is possible - I will check when I pull the oil pan off this winter.

Maybe this is operating as good as possible!


Link to comment
Share on other sites


no,if I remember right you can mount the Bearingscaps only in one direction because of an radius on one Side and upper and lower are similar.

What do you can try is to eleminate the Crankhousing inner pressure with let them suck it about the Carb feet or Airfilter,like the newer Engines with a PCV Valves do that.Maybe you must close your Breather for maximum suck.

I have heard from this AFTER swaping my Engine ,that would maybe help ... but I hadnt try that.

And yes,i can drive very easy in the Traffic,because I have a lighten up, stripped Coupe and its to handle like a very smaller Sportcar,its not run like a heavy full equipped Sedan. Another Reason for my agile Car is that the Flywheel is relieved for 3 Kg ,no Fan Blades on the Waterpump (E-Fan ) and the short 4.44:1 Ratio, and so the accelerating feeling is like a twostroke Engine,also with the old 248 !

The travel Speed on the Autobahn is now 60 mph ,80 mph is without Problems possible,because of the finebalanced Crank and better modern Shockabsorber in front. With the 248 was it the same,but with amazing outpressing Oil at the rear Mainbearing,like yours.

A Century Ratio ( 3.7:1 I think..) would be nice with the closed Drivetrain,but you know, this is extremly hard to get.

Im not will destroy the original Condition from my Car, its a rustfree Survivor .

Gruß aus Deutschland :)

Edited by jenz38 (see edit history)
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...