The Ford Barn

Rich-CO · 08-06-2013, 10:27 PM

Hello all---Will a 4" Merc crank fit into a '38-40 221 inch block without grinding clearance at the bottom of the cylinders?
Rich

flatheadute1934 · 08-06-2013, 11:43 PM

Yes works best with the later rods but can be used the floating rods from 38-40

Ol' Ron · 08-07-2013, 09:31 AM

This only works if you grind the crank down to 1.998. a better and cheaper idea would be to bore the block to 3 3/16 and use Merc pistons and rids

Karl Wolf · 08-07-2013, 06:43 PM

...one could also use the French 6 7/8" rods...
I think that it might work out better to use a 59 block (46-48)
Karl

rotorwrench · 08-08-2013, 12:49 PM

I read an article about using a 4-inch crank in the 21 stud 37 block but they had to cut the couterwights down a bit if I remember correctly plus match the mains. If a person was going to use floating rod bearings, they might as well offset grind the crank for 4 1/8" stroke at the same time.

Bluebell · 08-08-2013, 08:09 PM

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Rotorwrench, that might lead to problems of clearance, which I think Ol' Ron was eluding to, with the rods at the bottom of the bore?

Ol' Ron · 08-08-2013, 10:28 PM

I installed an 8ba crank in a 37 block by turning down the mains to 2.398, I then bored the block for stock 3 3/16 pistons. This way the 8BA rods fit thru the bore to the crank. There was no need to clearance the crank weights, everything spun quite well in AV8 Pauls engine for 22000 miles whrn it spun a rod bearing. Walt Dupont fixed it and it's back in his car. I think this could have been done with a 4" crank, but we weren't sure. Paul was looking for a 4' crank for future use I understand.

08-06-2013, 10:27 PM	#1
Rich-CO Senior Member Join Date: May 2010 Location: Boulder, Colorado Posts: 172	4" Merc Crank in '38-40 block Hello all---Will a 4" Merc crank fit into a '38-40 221 inch block without grinding clearance at the bottom of the cylinders? Rich

08-06-2013, 11:43 PM	#2
flatheadute1934 BANNED Join Date: May 2010 Location: Brooklin Posts: 205	Re: 4" Merc Crank in '38-40 block Yes works best with the later rods but can be used the floating rods from 38-40

08-07-2013, 09:31 AM	#3
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: 4" Merc Crank in '38-40 block This only works if you grind the crank down to 1.998. a better and cheaper idea would be to bore the block to 3 3/16 and use Merc pistons and rids

08-07-2013, 06:43 PM	#4
Karl Wolf Senior Member Join Date: May 2010 Location: Mill Valley,Ca. Posts: 1,509	Re: 4" Merc Crank in '38-40 block ...one could also use the French 6 7/8" rods... I think that it might work out better to use a 59 block (46-48) Karl

08-08-2013, 12:49 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: 4" Merc Crank in '38-40 block I read an article about using a 4-inch crank in the 21 stud 37 block but they had to cut the couterwights down a bit if I remember correctly plus match the mains. If a person was going to use floating rod bearings, they might as well offset grind the crank for 4 1/8" stroke at the same time.

08-08-2013, 08:09 PM	#6
Bluebell Senior Member Join Date: Nov 2012 Location: Tauranga, New Zealand Posts: 726	Re: 4" Merc Crank in '38-40 block Sponsored Links (Register now to hide all advertisements) Rotorwrench, that might lead to problems of clearance, which I think Ol' Ron was eluding to, with the rods at the bottom of the bore?

08-08-2013, 10:28 PM	#7
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: 4" Merc Crank in '38-40 block I installed an 8ba crank in a 37 block by turning down the mains to 2.398, I then bored the block for stock 3 3/16 pistons. This way the 8BA rods fit thru the bore to the crank. There was no need to clearance the crank weights, everything spun quite well in AV8 Pauls engine for 22000 miles whrn it spun a rod bearing. Walt Dupont fixed it and it's back in his car. I think this could have been done with a 4" crank, but we weren't sure. Paul was looking for a 4' crank for future use I understand.