[SEL] bore and sleave an engine question

Curt curt at imc-group.com
Thu Jul 6 06:53:08 PDT 2006


Bill,
Like I said yesterday there are a lot of opinions on boring vs. 
sleeving. Your 390 engine was already .030 over meaning someone made the 
decision to bore the engine once or twice before the decision was made 
to sleeve it. And that's my point with our old engines. Bore them only 
as needed to clean them up and fit an oversized piston. Then _years_ 
down the road if it has been bored so many times that it is getting 
really large, at that point fit a sleeve. But up until that point 
preserve as much of the original cylinder wall thickness as possible by 
doing a minimum bore and fit an oversized piston.  The economics are 
nearly identical for sleeving vs. new oversized piston if you make your 
own pattern. The piston castings are relatively inexpensive. If you own 
or have access to machineshop equipment, the piston machining process is 
3 or 4 hours tops.
I have yet to measure a used piston out of a cylinder that needed boring 
that isn't worn itself. You'll spend additional time truing that old 
part up and will need to make the sleeved bore undersized a little to 
account for work to the old piston.
We all tend to be intimidated with doing something out of the ordinary. 
For me, participating in and replicating the steps the engine 
entrepreneurs*** *had to go thru IS a big part of what this hobby is all 
about. Before I'm done with the hobby I hope to have experienced pattern 
making, building a cupola, casting parts off my patterns, machining 
parts, and assembly of those parts. So far I've experienced all these 
steps with the exception of building a cupola. Soon, very soon.....
Its great fun to challenge oneself and to continually learn.
Curt Holland
Gastonia, NC


bill at antique-engines.com wrote:

>Agree and here's why:
>A sleeve does not mean a lot of block material removal - a good sleeve is
>not that thick.
>A sleeve can be removed later and replaced again, should that unusual
>circumstance ever happen
>I collect another form of rare engine - AMC engines. Trust me, with the
>very high demand and the low availability of a 1970 390 block, they are
>treated like gold, if you have a good one to get rid of, you can trade it
>for most anything else. A few folks race with them, and the discussion of
>to sleeve or not to sleeve comes up a LOT on the forums. I mean a LOT. The
>consensus is that you are not hurting the block - the sleeve does no
>damage. The sleeve might actually be saving a block as the wear and abuse
>is on the sleeve. Sleeved blocks see fewer problems.
>In my case, my 390 had already been bored to .030 over. The forum members
>and machine shop all agreed - SLEEVE IT. The sleeve job was only 80 bucks
>a hole and is so good it's hard to tell there are sleeves in it. I can in
>the future have it done again should I get crazy with it - but having the
>rare one-year-only 1970 390 block, probably won't happen! In fact I put
>later heads on it to reduce compression and installed step-dish hyper
>pistons to avoid this sort of damage.
>
>Bottom line - the amount of material removed by a good shop when
>installing good sleeves is minimal.
>You can then use original pistons, retaining originality and the ability
>to find standard parts - meaning instead of finding some rare or unusual
>size piston, etc. - you simply drop in a standard original piston. The
>engine is not modified.
>A sleeve can be replaced if need be - but if you resleeve and wear it that
>darned much - wow - but it can be resleeved later.
>Most blocks, including AMC v8 blocks, have a LOT of meat to them. You can
>remove a lot of material without damage, but boring the block to oversize
>and installing larger pistons, well, there you are wearing on the block
>again, so in the future someone is gonna have to sleeve it anyway.
>
>It's hard to say here, but seems most car and tractor fellows readily opt
>for sleeves and the many advantages, none of them suggesting that they are
>doing any damage and if anyone is gonna fuss over messing up a good block,
>trust me, these AMC folks will be the first to scream bloody murder. 3 to
>5K for a rebuild is nothing.
>
>In years of auto rebuilding, I've not seen any problems with sleeves, even
>with subsequent rebuilds.
>
>Bill
>
>  
>
>>I can understand what Curt is saying to an extent but when I can bore
>>and sleeve our 6hp Famous for free but to get a piston cast will cost
>>me, I go for the sleeve any day and you can't tell it's been done no
>>matter how hard you look.
>>
>>Ben
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>>
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