Old FH race cranks ( before the 8BA )

[3W Hank]

A 3.7/16" bore ( MAX ) and a 3.785" stroke is over 280 cu in.
A 3.75" stroke ( same bore ) is 278 cu in )
Not much gain.

A classic Merc 4" and + 1/8" bore is 278 cu in.
3.75" stroke and 1/8" bore is 258 cu in.

My 41 truck-Merc/rised intake block is told to has ca 0.25" wall now ( sonic tested in Ca ) and bore is 3.3125" or 1/8" over std.
If I would 'dare' go 3.4375" I has wall that get thinner by 0.06".

[Bored&Stroked]

I would definitely have that block sonic tested again . . . as I find it hard to believe that it has that much wall thickness left. I have sonic tested a lot of these blocks and have never found one to have that amount of thickness after a .125 overbore. With that said, it is possible - but I have not seen it.

When you have it sonic tested have them do each cylinder in 12 places - top, bottom and middle of the cylinder - on four 90 degree locations at each level.

I would love to see the numbers!

[3W Hank]

Yes, its still at the car shipper in LA.
No Swedes by cars theesedays as our money is nothing worth to USD plus everything has become expensive here to. So imports is zero to no..
Deal was in next box over, but they could not tell.
As soon its here I will get it tested, but I’m dont rely much on this tests as we are checking a machined sleeve.
Big bore is cool but can lead 8 sleeves, or just a hone at +125 and custom pistons.

[Ol' Ron]

Back in the early days 2 3\8 was the standard over bore. And yes a few 3 7/16 as well, Some times the compression was toooooo hi!!!\Gramps

[Bored&Stroked]

If I'm building a high-performance flathead, I do not like to have more than about 2 sleeves in a block. When you get to 8 sleeves, it can really weaken the deck as most of the material that tied the deck to the rest of the block has been removed (to bore for sleeves).

[3W Hank]

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Yes I’m aware of that issue.

[tubman]

Originally Posted by Bored&Stroked

If I'm building a high-performance flathead, I do not like to have more than about 2 sleeves in a block. When you get to 8 sleeves, it can really weaken the deck as most of the material that tied the deck to the rest of the block has been removed (to bore for sleeves).

I hate to get down to splitting hairs, but is that per block or per side? Also, does it make a lot of difference if they are next to each other or not?

(Asking for a block I hope I'll never have to use.)

[tubman]

Originally Posted by Bored&Stroked

If I'm building a high-performance flathead, I do not like to have more than about 2 sleeves in a block. When you get to 8 sleeves, it can really weaken the deck as most of the material that tied the deck to the rest of the block has been removed (to bore for sleeves).

I hate to get down to splitting hairs, but is that per block or per side? Also, does it make a lot of difference if they are next to each other or not.

(Asking for a block I hope I'll never have to use.)

[3W Hank]

I did checked out this crank today.
Std on both rod & mains.
Long nose and big mains/rods so it must be a 1939 early as rear seal was a slung.
Are that design bad, or caused leaks ?
If I got it right under 39 it was both slung and rope, so it cant be a 1940's crank.
Weight was 70.5 LBS or 32 kg.
Don't know weight of a 1945 crank or a Merc 4".

[Ronnieroadster]

Originally Posted by 3W Hank

I did checked out this crank today.
Std on both rod & mains.
Long nose and big mains/rods so it must be a 1939 early as rear seal was a slung.
Are that design bad, or caused leaks ?
If I got it right under 39 it was both slung and rope, so it cant be a 1940's crank.
Weight was 70.5 LBS or 32 kg.
Don't know weight of a 1945 crank or a Merc 4".

Hank Add at least 10 more pounds for the Merc.
Ronnieroadster

[3W Hank]

Yes I thought the Merc cranks is more beefy, but as I see it, can really the 1939 was lighter than ex 40 or 41 or exampla a 1945-47 crank.
This website said all cranks 36-41 had labyrinth seal.

As I heard it was a split 39 as early was sling, later was rope.

Question ; If anyone has a mid 40’s rope seal 59A crank, can you weight it ?

https://reds-vintage-parts.com/index...ch&search=1496

[3W Hank]

Well….It was a move in the idea here.
Did not want get up at 49 but I came over a old stroked Merc 4” at + 1/8” from the guy I bought my Merc 41 block from in Californnia.
So if I stay on bore + 1/8” I get 285 cu in.
Price was right but it needs to be re-grind on the mains to .020”.
New bearings included and a set of NOS 21A rods.

[Bored&Stroked]

If your current bores are tapered or out of round, the best thing is to go to the next oversize and bore/hone it again. I've done quite a few at 3 5/16 to .020.

You can get the pistons from Ross . . . just make sure they have the rings you'll be running before you order the pistons.

[3W Hank]

Yes I will ask what rings will fit to the new bore, I just hone it to they goes clean.