1942 Mercury 29A rear main seal- surprise surprise!

[RalphM]

Before I put the oil pan back on the Merc engine in the 1947, I thought I’d go ahead and change the front and rear main seals. I have a one piece modern seal from Speedway for the front, and I just pulled the rear cap off, and I got a surprise. There is no rear main seal. I guess I’ve just been doing too many 59 AB’s and 8BA’s
So that being said, is there anything I should do to it other than cleaning, before I put it back together?

[Bored&Stroked]

Given the crankshaft you have in it, there isn't much more you can do. When I put later crankshafts in these engines (like 49-53 Merc cranks), I put the later 59AB type rear-main seal in as well. The later pot-metal seal-plates will work in the 42 engine - allowing you to use the rope-seals. The crankshaft will have a ground/polished seal surface in the area where you see the raised "slinger".

Another possibility (though I haven't closely inspected your type of crankshaft) - would be to have a crank grinder remove the slinger and grind in the later style seal surface - then switching out the two seal plates and use the rope seals. My bet is that this approach would work (and has probably been done before).

Good luck!

[mercman from oz]

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1942 Mercury 29A rear main seal