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Old 01-14-2014, 05:41 PM   #1
1930artdeco
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Default max overbore

Hi all,

The engine that I took out of my car was bored .125 over. Assuming (and I know what it stands for) there are no cracks in the block is there enough meat left to bore and sleeve it?

I was thinking of trying to bring it back slowly in my off time a little at a time as I am in no hurry. But if it can't be sleeved then I will scrap it.

Mike
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Old 01-14-2014, 05:47 PM   #2
James Rogers
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Default Re: max overbore

To sleeve a Model A engine, I bore it .123 over 4.00" and use a sleeve with .125 walls. That way it can be bored all the way to 4.00" in the future.

The answer to your question is, YES.
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Old 01-14-2014, 05:56 PM   #3
1930artdeco
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Default Re: max overbore

Thanks James.
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Old 01-14-2014, 06:01 PM   #4
Dave in MN
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Default Re: max overbore

FWIW: If the engine is not "a matching number" original to the car, it may be less expensive to purchase a good block than sleeve 4 cylinders. I was just thinking of the cost! 4 sleeves installed but not final bored would be about $400.00 in my area.

James is correct in his answer to your question.

Good Day!
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Old 01-14-2014, 06:18 PM   #5
lindy williams
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Default Re: max overbore

Rich Falluca now bores Model A's to .140" over stock without using sleeves. He has had pistons made to that size.
antiqueenginerebuilding.com
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Old 01-14-2014, 06:48 PM   #6
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Default Re: max overbore

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At .125 you should have at least 3 more rebuilds WITHOUT sleeving.
Hone it to clean the same size on all 4. Order pistons from Ross to fit.
We routinely bore to .156 for racing engines.
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Old 01-14-2014, 06:50 PM   #7
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Default Re: max overbore

Pete: What head gaskets do you use? Thanks
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Old 01-14-2014, 06:56 PM   #8
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Default Re: max overbore

Copper.
When I bore to .156, I offset the bar to keep the area between cylinders at maximum.
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Old 01-14-2014, 07:16 PM   #9
H. L. Chauvin
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Default Re: max overbore

Hi 1930,

Do not know all of your existing engine details, existing cylinder measurements, & engine history; however, FWIW, I had a .125 bore on all (4) cylinders when I recently bought this last Model A.

Engine previously ran with only non-detergent oil & created such a sludge mess throughout.

Removed old (4) pistons & rings, honed cylinders, & provided new .125 pistons & new .125 rings after seeing hardly any ridge & after checking bore diameter throughout with telescoping gauge.

Does not smoke, uses no oil, lots of compression, & with new full flow oil filter & Hi-Boy K & N Air Filter, it will certainly outlast me with 5W40 Rotella Oil.

Years ago with non-detergent oil not changed regularily, ring grooves got clogged with non-detergent sludge -- then rings began to stick in ring grooves & not expand -- with piston up & down speed, rings got pressed in at smaller diameter lower ends of cylinders & could not expand fast enough when they reached larger diameter tops of cylinders; hence lost compression.

Years ago thousands of engines were very successfully fitted with new pistons & rings without re-boring.

Even though engine manufacturers always write very critical specifications on when to re-bore, please remember that manufacturers also have a marketing department & stock holders, always hoping that they can sell as many oversized manufacturers parts as possible, as well as dealerships wanting to get their share of oversized parts & labor sales & profits.

Maybe your existing .125 cylinders are possibly not too worn to require re-boring.

If not already done, maybe check them out.
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Old 01-14-2014, 07:54 PM   #10
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Default Re: max overbore

I wouldnt sleeve it if you dont have to. It can cause heat transfer issues and cause pistons to fail...this is what happened to me, but the shotty sleeve installation was just part of the shotty machine work that was performed. I know a guy who got his to .200 over, but that was not a street drivable motor. it was for the salt flats, but if i were you id explore all other options before installing a sleeve.
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Old 01-14-2014, 10:34 PM   #11
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Default Re: max overbore

I have bored them .155 over. I would rather have a engine with out sleeves.
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