Has anybody done this? I know it can be done but I'm wanting to know the machining required for the rear main seal and what if anything has to be done to the thrust..and also the 8ba being a longer crank does that effect anything? Thanks in advance
It can be done and has been done, and as far as I can tell all the cuts should be possible on normal crank grinding equipment run by an intelligent machinist, unlike the mods needed for babitt flatheads. This crank for the loose main 1936 LB is same crank used in 1937-8 21 studs and 1938 only 24 stud engines. Diameter of mains is of course reduced and I think one is cut to slightly longer...do a search on Ford barn, Ol'Ron as poster and crank or crankshaft as search term. He lays it out. Boring to 3 3/16 is risky, you might be well advised to get special pistons and keep bore small. You could of course offset the rod journals to 4 1/8, or just cut them down to use the lighter rods. Big rods with small bore must be ***embled to pistons in engine, and of course the big rods are heavier. Length difference (39-53, all cranks) is in the nose only, lengthened to allow the '39-41 crank mounted fan. You could cut it to fit '32-38 pulley or just use a later pulley. Seal...1937-8 uses replaceable zinc casting for upper seal...does LB have that? I don't have one to look at. I'd work towards using the later seal and avoid slinger setup!
Ya it uses the replaceable castings, I am going to use the big rods and stay with just a .020 bore on the block so I'll have to ***emble them in the engine which is no biggie. Just trying to figure out the rear main and if I have to change anything else on the mains besides turning the crank journals smaller to fit
This is one of Ron's cryptic posts...I think there are others on this. "I put an 8ba crank in a 37 block for Paul Howard, he wanted to keep the 21 studder looking stock. The only problem I had was the width of the front and center maines had to be widened .050" +/- some. The rod bearings will require 21A rods. You might want to consider re balancing it. You could also uz a 4" crank and build a 255. Just thinking. Good luck."
The Jalopy Journal
