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Master six crank seal


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   These are notes from doing the rear main seal on my 1925 Buick Standard.  I have a different clutch so I cannot help with that.     Hugh


Rear Main Seal

1)     There are two wire retainers used with the original 1/4" x 1/4" cross section cork rear main seals.  The purpose of the 2 wires is to prevent the cork seal from rotating in the bearing cap and block.  The .035 wire is stiff and you could make new ones if you needed to easily, just use a wire that is a little difficult to bend.  A lot of the wire available is very pliable.  This is hardened like wire for a spring.  Notice that there is also a tiny hole in the bearing cap and in the block just near the parting line.  Just the corner of the wire goes into the hole and that is what keeps the cork seal from spinning.  


As a modern upgrade, I have installed the “Best Gasket” rope seal #6340 that I purchased from Egge Machine in California.  This requires drilling a small 1/16" hole in the middle of the bearing cap seal area and installing a very small 1/16" diameter roll pin, so I no longer need the wires. The seal comes with good instructions on installation, but there are a few issues.  I am being very careful not to overstress the casting section that holds the rear main seal.  I used a 1/16” punch to make a hole in the rope seal to fit the roll pin to prevent rotation.  I pushed the rope seal in the cap and the block as far as I could by hand. 



Initial fit of the rear main seal. I found a socket the exact size as the rear main seal diameter.  How lucky is that.  Very slightly smaller would be OK too, but probably no more than .010 smaller OD.  Maybe could use shim stock around a socket if necessary.  The socket should stay behind the babbit surface.  I tried pounding the socket to push the rope seal into place but was having some trouble getting the socket all the way to the bottom of the groove where it would compress the rope.  I put the rope into the groove as deep as I could.  I followed the directions included with the rope seal and cut the ends of the rope “proud” or above the machined surface by .015” using the shim stock that was supplied with the seal kit. 

·       I then used the socket and began slowly pulling the bearing cap down on the rope seal.  The rope seal is oil impregnated.  I did not want to hydraulically overpressure the bearing cap where the seal is.  I wanted to pull it down slowly so that the excess oil could escape.  I took my time cross tightening the 4 nuts in the bearing cap and only using a 3/8 drive hand socket.  I also occasionally rotated and wiggled the socket to be sure that it still was not binding and overpressuring the oil seal retainer.  I only pulled it down tight to where the mating surfaces touched.  


2)      Then remove the cap and clean up any oil that squeezed out.



Install the crankshaft

·       The 6 special flywheel bolts must be installed in the crankshaft prior to placing the crankshaft in the block.  Do not pull them up tight until the flywheel and upper bell housing is installed. 


·       bearing cap prep - , the rope seal has been pre squished so to speak above.  I used red assembly lube on the bearing surface and on the rotary surface of the rear main seal.  I used Permatex copper coat gasket in a can.  The can copper coat is very thin.  It comes with a ball applicator, but I used a small paint brush to control the application better.  I wanted the coppercoat on the mating surface, and assembly lube on the bearing surface.  I did not want coppercoat on the bearing surface or the rope seal ends.  Because this is a mating surface that can leak oil thru the surface, I wanted to keep oil from migrating thru to the outside.  The 2 rear main bolts are also outside the oil pan which is unusual.  I wanted to prevent an oil leak down these 2 bolts so there is sealant around the mating surface of the 2 bolts.  The rest of the surface has compound on it just to be evenly spread.  


·       Install the bearing caps on the main bearings and the connecting rods.  You can plastigauge again if you like.  Ensure the motor spins freely. 

·       Install the cotter pins on the connecting rod and main bearing bolts. 



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