The Ford Barn

Seth Swoboda · 03-20-2023, 07:26 PM

I have a 37-38, 21 stud, 221ci engine that is currently at .080 over bore. Four of the cylinders have some scaring in them that will require another overbore. The engine is otherwise very nice.

I would like to bore the engine .125 over. This would make the new bore size 3.1875, the same as a standard sized 59A engine. Pistons and rings would be easier and cheaper to acquire.

The question is the head gasket. What are you guys doing for 21-stud head gaskets on a .125 overbore?

**Let's also assume that the cylinder wall thickness checks out okay for the .125 overbore in this case.

Brian · 03-20-2023, 07:59 PM

cometic make gaskets in various thicknesses that accommodate that bore size...not cheap!

Dave/Green Bay · 03-20-2023, 08:26 PM

I have a 35 221 and was told .125 was taking a chance. I would sonic test wall thickness before boring. Dave/Green Bay

Brian · 03-20-2023, 11:31 PM

I bored a 37 block out to 3 3/16", fitted a 4" stroke crankshaft. Sonic tested the walls before hand, had 0.145" wall thickness minimum after boring to that size. Got Ross to make me custom flat-top pistons to suit...followed their instructions to the t, including using torque plates for final sizing. Not a good engine; it always had lots of crankcase pressurisation, detonated terribly [had 165 lbs compression], so thought I'd change the heads to lower compression....that's when I discovered all cylinders and piston skirts were scored.
I have built many engines over the years, from stock to 284 cubes, and this one was a disaster!. Subsequent to that, I had numerous emails and phone calls from another guy whose 36 LB engine was bored to .080" and his cylinders scored too, running cast pistons. 36 LB engines have thin cyl walls; boring them to .060" can be risky....
Now, I have no proof, but my theory is just because you can bore a 21 stud to xxx oversize, you run the risk off having the cylinder walls flex in use, leading to distortion and the resultant scoring, on account of them losing a degree of structural integrity.
To Dave/Green Bay, 35 blocks have thin cylinder walls [same as 36 LB]. 37 blocks are somewhat thicker, and, as I discovered can still be problematic at such an oversize.
Seth, with your 37 block, a possibly safer option would be to sleeve the dodgy cylinders, alternatively, find another block.
My opinions/experience only, take it for what it's worth.

Ol' Ron · 03-21-2023, 08:00 AM

Had a 37 engine bored to 3 3/16 and 8BA crank, L-100 cam and a 105 MPH speeding ticket. Just a good running engine in a Model A roadster.
Gramps
This was a prelude to installing a 4" crank, but ranout of funds. Car was in the Ford barn several times. I'll look for it.

Seth Swoboda · 03-21-2023, 09:02 AM

Sponsored Links (Register now to hide all advertisements)

I am going to sonic test the cylinder walls.

What I am gathering is the 24 stud, 221ci engine that I bored out to .125 has thicker cylinder walls than the 37-38, 21 stud engines?

All of that aside, what about the head gasket question?

Brian, I asked my machine shop about sleeving back to .080 becuase the pistons and rings that are in this engine are new. I would be able to use them and not have to buy new. That is not a problem. The cost rises from $250.00 to bore it another .045 to over $1200 for sleeving and decking. Which is not a huge issue I wanted to try the path of least cost.

Seth Swoboda · 03-21-2023, 04:13 PM

I must have stumped the fordbarn.

Having my good friend Michael Driskell contact Best Gasket, a 21 stud gasket for a .125 overbore does not exsist outside of custom made. As Brian mentioned above.

The consenses is also that the cylinder wall most likely will not tolerate this overbore. It has been done before as Old Ron has spoken of. I'd bet H&H has done it. It could be a "luck of the draw" situation. Pardon the cliche.

Perhaps because the .080 pistons and rings are new, I should have the block sleeved back to a .080 overbore so that I can still use the new pistons and rings?

Ol' Ron · 03-21-2023, 04:40 PM

I think tje 24 stud gasket will fit, but you have yo add some holes. That was along time ago.
Gramps

35fordtn · 03-21-2023, 06:12 PM

Roy the owner of best gasket claimed there gaskets are good to .108” for futur knowledge. He recognized the “maybe” a person could cut a relief on the piston edge and get away with .125” and naturally discouraged that. He really stands behind his products and obviously went with the side of caution on the question. They are a stand up company and for our vendors great to deal with. I know many have done the .125 on 37’s and I have driven cars done that way but have never built one that way. I am still curious if maybe a felpro gasket or even NOS has a larger firing ring. I used to stock Felpro and have nos but again given the support best gasket co gives us I have depleted everything else so nothing to compare to.
I am also interested in what you guys have used for gaskets as I too have a .080 engine I wish to do to .125” sonic testing showed me it could easily handle it

frnkeore · 03-22-2023, 03:30 AM

Here is what you have to work with on a 21 stud, using Fords engineering drawings:

1. The distance from the center of the bore, to the center of the bottom stud, is 1.937.
2. With a 3.188 bore, the distance from the center of the bore, to the edge of the bore is, 1.594.
3. 1.937 - 1.594 = .343
4. you have to subtract 1/2 the stud diameter, .343 - .219 = .124. Edge of stud, to edge of cyl bore.
5. I have 2 sets of head gaskets. one has a .500 hole for the studs and the other has .480 holes so, I'll use .490
6. Now, we have 1/2 of .490 hole = .245. .343 - .245 = .098 Edge bore to edge of stud hole.

Head gasket bore for the Ford gasket is = 3.13 (late gasket), Victor = 3.108. Here we have the head gasket inside the cylinder by .04 - .029

The fire ring on the Victor goes from the head gasket bore to the edge of the stud hole on the bottom BUT, on the top side, it's only .094 wide and extends to only what would be a 3.296 bore, leaving only .054 sealing the bore, on the top side.

One last thing, is that the outside diameter of the 21 stud cylinder wall for, at least '32 - '36 (the last 2 years, '37, early '38, may be different) is 3.38. If there is no core shift and no erosion, that will give a maximum of .096 cylinder wall thickness. So, a sonic test would be warranted, before boring to 3.188.

All head stud locations are in the same place for 21 & 24 stud engine except for the bottom row so, you could cut a new hole BUT, the gasket bore, will most likely be larger (maybe not for the 24 stud 221) for the 3.188 bore engine and may not seal, at all doing it that way. You'll also have to be very careful locating the hole, before punching, even if there is some fire ring left. You could overlay the two gaskets to see if there would be enough fire ring left.

The lower stud on the 21 stud engine, is directly, in the center of the bore, at the bottom.

So, what I would suggest, is that you try to get a gasket that the top fire ring ends at the stud hole on both sides and that you sonic test, before boring.

Y block and later engines, had the cylinders thicker on the thrust sides but, these Ford drawings don't show that.

Seth Swoboda · 03-22-2023, 08:42 AM

I think I'll either find another engine or sleeve this engine back to .080 so that I can use the new bearings, pistons and rings that are installed. Sleeving and decking will cost me about $1200.00, but I'd not have to buy new pistons. It's hard to find a good running flathead for $1200-$1500. Of course I'd have to buy a new gasket set.

The history of this engine is my grandfather put it together back in the late 70's or early 80's. My dad can't remember. It has a valve job, adjustable lifters and is very clean.

Why he put it together with the scars in the cylinder wall is a question I'll never get answered becuase he has been deceased for 22 years. I think the mentality at the time was run it and not worry.

03-20-2023, 07:26 PM	#1
Seth Swoboda Senior Member Join Date: May 2010 Location: Southern Illinois Posts: 3,785	1937-1938, 21 stud engine bored to .125 I have a 37-38, 21 stud, 221ci engine that is currently at .080 over bore. Four of the cylinders have some scaring in them that will require another overbore. The engine is otherwise very nice. I would like to bore the engine .125 over. This would make the new bore size 3.1875, the same as a standard sized 59A engine. Pistons and rings would be easier and cheaper to acquire. The question is the head gasket. What are you guys doing for 21-stud head gaskets on a .125 overbore? **Let's also assume that the cylinder wall thickness checks out okay for the .125 overbore in this case.

03-20-2023, 07:59 PM	#2
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,829	Re: 1937-1938, 21 stud engine bored to .125 cometic make gaskets in various thicknesses that accommodate that bore size...not cheap! __________________ Unfortunately, two half wits don't make a whole wit!

03-20-2023, 08:26 PM	#3
Dave/Green Bay Senior Member Join Date: May 2010 Location: Green Bay Posts: 391	Re: 1937-1938, 21 stud engine bored to .125 I have a 35 221 and was told .125 was taking a chance. I would sonic test wall thickness before boring. Dave/Green Bay

03-20-2023, 11:31 PM	#4
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,829	Re: 1937-1938, 21 stud engine bored to .125 I bored a 37 block out to 3 3/16", fitted a 4" stroke crankshaft. Sonic tested the walls before hand, had 0.145" wall thickness minimum after boring to that size. Got Ross to make me custom flat-top pistons to suit...followed their instructions to the t, including using torque plates for final sizing. Not a good engine; it always had lots of crankcase pressurisation, detonated terribly [had 165 lbs compression], so thought I'd change the heads to lower compression....that's when I discovered all cylinders and piston skirts were scored. I have built many engines over the years, from stock to 284 cubes, and this one was a disaster!. Subsequent to that, I had numerous emails and phone calls from another guy whose 36 LB engine was bored to .080" and his cylinders scored too, running cast pistons. 36 LB engines have thin cyl walls; boring them to .060" can be risky.... Now, I have no proof, but my theory is just because you can bore a 21 stud to xxx oversize, you run the risk off having the cylinder walls flex in use, leading to distortion and the resultant scoring, on account of them losing a degree of structural integrity. To Dave/Green Bay, 35 blocks have thin cylinder walls [same as 36 LB]. 37 blocks are somewhat thicker, and, as I discovered can still be problematic at such an oversize. Seth, with your 37 block, a possibly safer option would be to sleeve the dodgy cylinders, alternatively, find another block. My opinions/experience only, take it for what it's worth. __________________ Unfortunately, two half wits don't make a whole wit!

03-21-2023, 08:00 AM	#5
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,855	Re: 1937-1938, 21 stud engine bored to .125 Had a 37 engine bored to 3 3/16 and 8BA crank, L-100 cam and a 105 MPH speeding ticket. Just a good running engine in a Model A roadster. Gramps This was a prelude to installing a 4" crank, but ranout of funds. Car was in the Ford barn several times. I'll look for it.

03-21-2023, 09:02 AM	#6
Seth Swoboda Senior Member Join Date: May 2010 Location: Southern Illinois Posts: 3,785	Re: 1937-1938, 21 stud engine bored to .125 Sponsored Links (Register now to hide all advertisements) I am going to sonic test the cylinder walls. What I am gathering is the 24 stud, 221ci engine that I bored out to .125 has thicker cylinder walls than the 37-38, 21 stud engines? All of that aside, what about the head gasket question? Brian, I asked my machine shop about sleeving back to .080 becuase the pistons and rings that are in this engine are new. I would be able to use them and not have to buy new. That is not a problem. The cost rises from $250.00 to bore it another .045 to over $1200 for sleeving and decking. Which is not a huge issue I wanted to try the path of least cost.

03-21-2023, 04:13 PM	#7
Seth Swoboda Senior Member Join Date: May 2010 Location: Southern Illinois Posts: 3,785	Re: 1937-1938, 21 stud engine bored to .125 I must have stumped the fordbarn. Having my good friend Michael Driskell contact Best Gasket, a 21 stud gasket for a .125 overbore does not exsist outside of custom made. As Brian mentioned above. The consenses is also that the cylinder wall most likely will not tolerate this overbore. It has been done before as Old Ron has spoken of. I'd bet H&H has done it. It could be a "luck of the draw" situation. Pardon the cliche. Perhaps because the .080 pistons and rings are new, I should have the block sleeved back to a .080 overbore so that I can still use the new pistons and rings?

03-21-2023, 04:40 PM	#8
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,855	Re: 1937-1938, 21 stud engine bored to .125 I think tje 24 stud gasket will fit, but you have yo add some holes. That was along time ago. Gramps

03-21-2023, 06:12 PM	#9
35fordtn Senior Member Join Date: Aug 2010 Location: McMinnville, TN Posts: 2,327	Re: 1937-1938, 21 stud engine bored to .125 Roy the owner of best gasket claimed there gaskets are good to .108” for futur knowledge. He recognized the “maybe” a person could cut a relief on the piston edge and get away with .125” and naturally discouraged that. He really stands behind his products and obviously went with the side of caution on the question. They are a stand up company and for our vendors great to deal with. I know many have done the .125 on 37’s and I have driven cars done that way but have never built one that way. I am still curious if maybe a felpro gasket or even NOS has a larger firing ring. I used to stock Felpro and have nos but again given the support best gasket co gives us I have depleted everything else so nothing to compare to. I am also interested in what you guys have used for gaskets as I too have a .080 engine I wish to do to .125” sonic testing showed me it could easily handle it

03-22-2023, 03:30 AM	#10
frnkeore Senior Member Join Date: Jul 2019 Location: Southern Oregon Posts: 782	Re: 1937-1938, 21 stud engine bored to .125 Here is what you have to work with on a 21 stud, using Fords engineering drawings: 1. The distance from the center of the bore, to the center of the bottom stud, is 1.937. 2. With a 3.188 bore, the distance from the center of the bore, to the edge of the bore is, 1.594. 3. 1.937 - 1.594 = .343 4. you have to subtract 1/2 the stud diameter, .343 - .219 = .124. Edge of stud, to edge of cyl bore. 5. I have 2 sets of head gaskets. one has a .500 hole for the studs and the other has .480 holes so, I'll use .490 6. Now, we have 1/2 of .490 hole = .245. .343 - .245 = .098 Edge bore to edge of stud hole. Head gasket bore for the Ford gasket is = 3.13 (late gasket), Victor = 3.108. Here we have the head gasket inside the cylinder by .04 - .029 The fire ring on the Victor goes from the head gasket bore to the edge of the stud hole on the bottom BUT, on the top side, it's only .094 wide and extends to only what would be a 3.296 bore, leaving only .054 sealing the bore, on the top side. One last thing, is that the outside diameter of the 21 stud cylinder wall for, at least '32 - '36 (the last 2 years, '37, early '38, may be different) is 3.38. If there is no core shift and no erosion, that will give a maximum of .096 cylinder wall thickness. So, a sonic test would be warranted, before boring to 3.188. All head stud locations are in the same place for 21 & 24 stud engine except for the bottom row so, you could cut a new hole BUT, the gasket bore, will most likely be larger (maybe not for the 24 stud 221) for the 3.188 bore engine and may not seal, at all doing it that way. You'll also have to be very careful locating the hole, before punching, even if there is some fire ring left. You could overlay the two gaskets to see if there would be enough fire ring left. The lower stud on the 21 stud engine, is directly, in the center of the bore, at the bottom. So, what I would suggest, is that you try to get a gasket that the top fire ring ends at the stud hole on both sides and that you sonic test, before boring. Y block and later engines, had the cylinders thicker on the thrust sides but, these Ford drawings don't show that. __________________ Frank '35 Ford Model 51 '48 Ford F3 '54 Ford Tudor Mainline

03-22-2023, 08:42 AM	#11
Seth Swoboda Senior Member Join Date: May 2010 Location: Southern Illinois Posts: 3,785	Re: 1937-1938, 21 stud engine bored to .125 I think I'll either find another engine or sleeve this engine back to .080 so that I can use the new bearings, pistons and rings that are installed. Sleeving and decking will cost me about $1200.00, but I'd not have to buy new pistons. It's hard to find a good running flathead for $1200-$1500. Of course I'd have to buy a new gasket set. The history of this engine is my grandfather put it together back in the late 70's or early 80's. My dad can't remember. It has a valve job, adjustable lifters and is very clean. Why he put it together with the scars in the cylinder wall is a question I'll never get answered becuase he has been deceased for 22 years. I think the mentality at the time was run it and not worry.