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Old 03-27-2017, 02:03 AM   #1
Fe26
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Default Post war replacement blocks for 81a

Hi guys,
It's been awhile since I last logged on...

I have a post war replacement block for an 81a motor that has a 3/16th bore and is also factory relieved. My question is, how far can these be bored out. One cylinder has a nasty gouge (about 50 thou) from a gudgeon (wrist) pin circlip coming loose and a piece of the pin broke off and gouged the bore.

I don't need or want this block, so I'm wondering if there is any demand for these things, or is it just scrap value. The block is in New Zealand so V8 blocks are not as plentiful as the US.

Thanks.
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Old 03-27-2017, 05:12 AM   #2
Jay in Mass
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Default Re: Post war replacement blocks for 81a

I would not scrap it. Someone somewhere needs it.
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Old 03-27-2017, 06:00 AM   #3
Terry,OH
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Default Re: Post war replacement blocks for 81a

Ford installed hard steel sleeves in some of the 81A blocks you can do just one cylinder for repair.
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Old 03-27-2017, 11:18 AM   #4
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Default Re: Post war replacement blocks for 81a

Boring all out large or installing a sleeve and boring to next oversize is about the same amount of time so i would sleeve one cylinder if the rest looks good.
Going for 239 is working to if you want more displacement.
If the block is not badly rusted itīs a keeper !!
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Old 03-27-2017, 01:47 PM   #5
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Default Re: Post war replacement blocks for 81a

Your size dimension is a question mark for me. Is it 3 1/16 standard bore for 41A block or is it already out to 3 3/16 oversize? These have relatively thin walls but they will go out to 3.1875" as a general rule. If more than that I would get it sonic tested. If it is still near standard, the bore might clean up on that scored wall. If not, it would be worth sleeving as others have already mentioned.
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Old 03-27-2017, 05:10 PM   #6
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Default Re: Post war replacement blocks for 81a

Post war replacement blocks ive seen are 59A castings with small bore....if so definitely a keeper...
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Old 03-27-2017, 06:06 PM   #7
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Default Re: Post war replacement blocks for 81a

I have a 59 series long block that was cast in 1953 (stenciled on crate) that is 3 3/16 that came out of a Ford dealership in Texas in 1958. It had 8ba rods, cap screws on mains and 51 crankshaft. I left the bore at 3 3/16, put in a 4" crank and Ross pistons with the skinny rings. This motor is going into a 40 V8 business coupe with 4bbl, and Columbia rear end.
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Old 03-27-2017, 08:56 PM   #8
GB SISSON
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Default Re: Post war replacement blocks for 81a

Quote:
Originally Posted by deuce_roadster View Post
I have a 59 series long block that was cast in 1953 (stenciled on crate) that is 3 3/16 that came out of a Ford dealership in Texas in 1958. It had 8ba rods, cap screws on mains and 51 crankshaft. I left the bore at 3 3/16, put in a 4" crank and Ross pistons with the skinny rings. This motor is going into a 40 V8 business coupe with 4bbl, and Columbia rear end.
That's a great story. I'm glad you kept it at 3 3/16. Seems the market today is for boring right past all the oversizes and going straight to maximum for the series. I know the skeptics say there won't be a 'next generation' of flatheaders, but I know a few guys in their thirties who are living the flathead dream. We have to leave something for them to put oversize pistons in.
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Old 03-28-2017, 01:42 AM   #9
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Default Re: Post war replacement blocks for 81a

Quote:
Originally Posted by Jay in Mass View Post
I would not scrap it. Someone somewhere needs it.
Thanks Jay, I needed to hear that, seems a shame to scrap it.
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Old 03-28-2017, 01:44 AM   #10
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Default Re: Post war replacement blocks for 81a

Quote:
Originally Posted by Terry,OH View Post
Ford installed hard steel sleeves in some of the 81A blocks you can do just one cylinder for repair.
It would be so easy if this block did have sleeves but it doesn't. Someone may put there hand up for it.
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Old 03-28-2017, 01:46 AM   #11
Fe26
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Default Re: Post war replacement blocks for 81a

Quote:
Originally Posted by flatheadmurre View Post
Boring all out large or installing a sleeve and boring to next oversize is about the same amount of time so i would sleeve one cylinder if the rest looks good.
Going for 239 is working to if you want more displacement.
If the block is not badly rusted itīs a keeper !!
Will these blocks go out for 239? If so it has real potential. There is no rust on this block. As I understand it this was a truck application, hence the factory relieving. I was thinking the only use for this block was if someone wanted to fit a Supercharger. The question then becomes how far can it be bored.

Last edited by Fe26; 03-28-2017 at 01:55 AM.
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Old 03-28-2017, 01:49 AM   #12
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Default Re: Post war replacement blocks for 81a

Quote:
Originally Posted by jetmek View Post
Post war replacement blocks ive seen are 59A castings with small bore....if so definitely a keeper...
Yes it is the replacement block but it doesn't have the 59A letters on it. I heard that some US made replacement blocks were designated 41A. But this one would have come from Canada as a Commonwealth countries export.
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Old 03-28-2017, 02:30 AM   #13
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Default Re: Post war replacement blocks for 81a

I have a couple of these blocks , both 3 3/16th 60 thou over, you should have plenty of meat left.
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Old 03-28-2017, 10:27 AM   #14
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Default Re: Post war replacement blocks for 81a

That should be a C51A block unless it's a prewar C81A casting. They made them for a while after the war but we seldom hear much about them. I don't think the prewar Canadian blocks had the raised casting numbers on the front of the block like they did on the post war C59A and C69A blocks. It would be interesting to know if it has a raised casting ID on there.

The US designation was 41A for the post war 221 blocks and they had many characteristics of the prewar 81A block but most have the 59 on the bell. I think they used pewar type sand cores from the old engines inside the core boxes for the 59 series blocks for production casting. How they could ID them at the factory before painting is a mystery to me. You have to know the characteristics to tell them apart.

Last edited by rotorwrench; 03-28-2017 at 10:48 AM.
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Old 03-28-2017, 06:59 PM   #15
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Default Re: Post war replacement blocks for 81a

Thank you gentlemen, you have been very helpful.
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