Re: Mike's 53 Caribbean

Posted by DavidPackard On 2023/2/27 22:49:59

Kevin

It’s all about the seal, specifically the tolerance of the seal to accommodate a shaft that is translated off of the center of the seal . . . recognize it’s actually the seal that is translated away from the center of the shaft. At any rate, at a particular o’clock position the seal could be pinched tighter onto the shaft, while 180 degrees away from that position the seal/shaft operating clearance will be maximized. The area of pinch will undoubtable have accelerated wear and likely leak later in life, while the area that has the maximum clearance has a higher chance of leaking perhaps immediately. There is likely an amount of translation that when the harmonic balancer is installed the seal is compromised (destroyed).

The Packard shop manuals include a procedure to ensure the seal is not grossly translated with respect to the shaft by the use of a tool that is essentially a ‘dummy’ harmonic balancer hub with an undersized outside diameter. Feeler gauges are used to access whether the seal and shaft are centered. It is the ‘slop’ in the chain cover ’bolt circle’ that is the source of the potential misalignment. If the chain cover used alignment dowels the extra measurement check would not likely be required.

I seem to remember the SBC had dowel pins and no centering procedure for the chain cover, while the 235 straight six did not have dowels and used essentially the same centering procedure as Packard’s, that is a special centering tool when installing the gear cover. Fast forward to modern engines with gerotor oil pumps mounted concentric with the crank shaft. I’ve seen assembly procedures for those engines that somewhat repeat the checks that Packard recommended for the timing cover seal . . . lots of checks on whether concentricity has been achieved.

dp