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V12 Cylinder Wall Thickness

Phil Wimbish

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    I was wondering if there is any input on what people have used for minimum cylinder wall thickness?

 I know the thicker the better.  I have been told and have read that .125 is preferred but .090 could be acceptable.  After sonic testing I have at least one at .090.   This is a later block and I like the idea of the larger bore of 2 15/16”.  I do know about hot spots and weakness if the walls get too thin.

     Another thought, I know it wouldn’t be preferable, but could you sleeve one cylinder and use one slightly smaller piston to save the block.  If you keep the weights of the individual pistons close it doesn’t seem like it would be a huge difference, it’s not like these are 7000 rpm engines.

    I guess I hate to throw things out, plus I already have money and effort in this block.  It’s not like I need this engine to last 30,000 miles, how much are you going to drive an 82 year old car.  

   Thanks for listening and 

Stay Safeway!

Phil In Annapolis 

“38” Zephyr 3- window Coupe A Barnfind 50’s “Hot Rod”

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Common problem..........if building that motor....... your choice is gamble..........or sleeve EVERY ONE of the holes..............you could also Lock-Tite vaccuume seal the block...........we now do it on ALL our engines.......regardless of condition...........the problem is good engine work is no longer "the cheap part of the car project" and I see very few machine shop I would trust doing the work. Another interesting fact today is that many engines done in modern machine shops that are pre war end up running for a very short time, and then need to be done over again. I see this every day........in cars that are very expensive......over 250k. Too many people think its just an old flat head............same as a tractor. Well, a Duesenberg, V-12 Packard, and a V-16 Cadillac were cutting edge technology at the time....they were labor intensive when new..........and if you don't do EVERYTHING correctly, they will come apart. Most modern machine shops are "king of the shortcut" and do "cram and jam" rebuilds, using Chinese parts............there is a reason the world class restoration shops are busy.......there are few people left that do good work. I see the problem much more on the two coasts ..........places in the heartland that routinely build equipment are much better at early engines than the people who do production remanufacturing of modern stuff. So, just ask yourself what's more expensive.......taking a chance, and doing the engine twice......or doing it right the first time. I already know the answer........been there, done that.

Edited by edinmass (see edit history)
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A good machine shop should be able to install a wet sleeve in the one cylinder and still use the same bore as the others. If your bore is already .040" oversize (max recommended by Lincoln) and you need to clean up the bore, it would be a good idea to sleeve all of the cylinders back to stock. A problem with sonic testing is that it does not always find the thinnest point. .090" wall thickness could be good in one engine and not another. It depends where the thin spot is, compression and how bad the casting is rusted.


Do NOT try to run your engine with one undersized piston. It will never run right. All cylinders should have the same volume and compression for smooth running.


I would try to find a shop familiar with the Zephyr engine and ask for references. Then when you decide on the machine shop, take their advice.

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Hey Guys,

   Thanks for the input, it’s greatly appreciated!

I haven’t heard of the block sealant and could only find  one which sounds good, Irontite Ceramic Sealant, it does sound like a good idea to seal up porosity in the block.  Is that the product?

     The machinist that I used three years ago is 85 years old and did the work three years ago.  He has experience with these engines and a host of others and was/ is renowned in my area.  I’m not sure if he is still working.  He did not like the idea of having any “ wet” bore sleeves.  It seems like modern sealants would make it a decent proposition.  I respect his opinion, but  it doesn’t mean that another approach wouldn’t work.That would save me from sleeving all 12 cylinders. If anyone has firsthand experience doing a wet sleeve I would appreciate hearing more.  I thought a wet spot on the sleeve can make it possible to have a hot spot on the cylinder wall.  Also, I didn’t really think one slight smaller piston was a good idea, maybe just wishful thinking!

    Anyone have any recommendations for a machine shop in my area Maryland?


Stay cool!

Phil W


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