CMM Crank in earlier engines

frnkeore

frnkeore

Well-known member
I have found a 4" stroke Merc crank and I'm considering putting it in my later, block off plate, 21 stud engine.

I know that I have to turn the mains to 2.399 and the rod journals will be offset ground to 1.999 using the later bearings but, what about the rest of the crank dimensions, such as the front snout, rear seal and flywheel end?

It will go in my 35, Model 51 truck so, there are no radiator clearance issues.
 
why go through all that expense. the 37 eng is one of the best engins ford ever made leave it stock, if you want a souped up eng get a 8ba
 
Yes I did this with an 8BA crank, but kept the stock rods by boring the block to 3 3/16. So I didn't have to rebalance the assy. several people here have done that and it works quite well, but can be expensive.
 
#'s 1 & 2 main bearing journals, whilst being smaller dia, are also longer than the bigger journal cranks. So you'll need to address that too....and make a spacer in front of # 1 main to position the timing gear correctly. Just position the crank into the 37 block and you'll see what I mean.
 
I have to back tract, I got way ahead of myself.

I have been looking for a 59A crank, to offset grind to 3.85 stroke, to get my pistons .020 above the deck and got all excited when I found a local guy with a 4" Merc crank.

My problem is, that I already have my pistons and rings that are .080 over (I looked long and hard to find them, too) so, I have to give up the idea of using a 4" crank.

This guy says he has a "bunch" of FH cranks but, they are all '49 or later so, I can get a 8BA from him. Will the counter weights clear the block on a 8BA crank in my block?
 
A 59AB and a 8BA crank has about the same counterweights.
Are you .080 over 3 1/16 you will have no fun installing the later rods since they don´t fit the bore...
A -37 up block takes a 3 3/16 bore without problems and makes life easier installing a 8BA rotating asembly.
 
As for me, I won't bore a 21 stud that much. I have several original Ford drawing of the 21 stud blocks. The cylinder walls are 3.38 -3.40 diameter (depending on what drawing your looking at). Boring 3.188, only leaves a wall thickness of .096-.106 w/o core shift or erosion.

It also presents me with a whole new set of problems, since my aluminum heads are for flat top pistons.

My rods should work fine (remember the throws will be off set ground to 1.999), to my knowledge, the the only difference is that the early rods throws used a flanged rod bearing but, the rods are the same width as the later full floating rods.

The rational for this, is to get the pistons .020, above the deck, for my .060, compressed head gasket and FT pistons, using a 3.85 stroke.
 
Ron,
I assume your talking about Reds Headers? I looked over there, this morning and did a search for rear main seals and rear main seal adapter but, it didn't have a adapter listed.
 
Frank, 37 blocks had two styles of rear main bearing caps. Does your rear main cap have the inserted die cast piece for the slinger?
 
frnkeore, I use the top seal holders from an 8 N ford Tractor , I pay average of $5.00 each, then I buy the lower part of the seal holder on e bay for 40.00. better than paying 40.00 each for the top and bottom . That is what I use on the 1939-41 ,221 c.i. blocks to convert them to rear rope seals .
 
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Thank you all for your input.

Only the heads are off at the moment but, now I know what to look for when the crank comes out.
 
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