1cm Merc crank in a eary block?

so what is the best way to set up a 1cm Merc crank in a 1940 block. im mainly wouldering about crank pully, 40 or 8ba. does the pully end of the crank need to be turned down, or shorted? but also prefered rod for street. -josh

 

Try asking on the Fordbarn if you haven't, there are quite a few old flatty racers over there that know what to do.
Mike

 

you could try theFord Flathead 1932 to 1953 site. Sounds like a big job though.

 

This should all just bolt together, including '40 pulley--I think I have an 8RT engine with no pulley sitting near a '40 pulley at home and will verify.
IF you can find and afford the hardware, use any early 3 3/16 engine rods, 99-29-49A are all variants, or just use any '49-53 rods, not floaters but cheap and available. If your engine is really a '40, I think it is set up for slinger type seal. Swap I think for the seal retainers (the pot metal castings at back) from a postwar engine with rope seals. I think Red's headers can help with sealage questions and hardware.
Remember that if you have time, money, and a machinest on retainer, AND the crank is not much undersize, you can cut it fror 4 1/8" stroke and use 221 rods, 91 or 21 or 41A.
Is your engine a 221 or a 239?
Some early blocks will show very minor interference with rod to block using a Merc crank. Rare and minor problem, just needs slight grinding. Be sure to do a trial assembly and check all clearances carefully.

 

You will also need the 8BA flywheel and starter; a 10" clutch will fit OK, an 11" will not.

 

"I think I have an 8RT engine with no pulley sitting near a '40 pulley at home and will verify."
Aaaargh. Late engine had the evil '50-53 slinger spacer in place, and crank gear puller was at other house (the world's largest indoor junkyard). Found a 21A pulley, which definitely has same mounting length as the 1940 one, and some 8RT pulleys, and all seems right with this arrangement.
In fact, as I type this I remember that my '48 is running this arrangement and I didn't need to go through this exercise with the parts at all!

 

"IF you can find and afford the hardware, use any early 3 3/16 engine rods, 99-29-49A " are these the same as the rods in the 40 now?

 

What is the engine actually? If it's original '40 Ford, it left the factory with a 221 with small journal crank and 91A rods. These rods are the small ones used when cutting a Merc crank off center for a 4 1/8" stroke, and circle track people with displacement limits also cut big journal stock stroke cranks to this size for a miniscule improvement in weight and friction. They can also be used to save a Merc crank with rod throws beyond stock bearing sizes.
If you have a 239 engine, it should have the big journal rods if it has the pre-49 original crank. The 239's in 1940 Fords only came in a tiny number of police or special order passenger cars. Main use of the 99 engine was big trucks and of course Mercury. Most '40s eventually ended up with 239's, though, as the 59A engines pretty much became the replacement engine for everything. Best not to even worry about it--just takeitapart and see what actual parts and bore you have.