[SEL] piston rings and bores.

[bill at antique-engines.com]

A. They are so not needed in a typical gasoline engine (unless you seek
ultra-high performance)
B. I've heard some racers complain of gasses building up between the rings
and causing ring flutter and problems.
C. Some I've talked to who have tried them say they would not again.
D. See the truth on ring gap explained here:

http://kb-silvolite.com/feature.php?action=read&F_id=40

(My soon-to-be high-performance car engine will use KB hyper 28cc step
dish pistons on full-floating pins and a balanced crank assembly)

On a stationary, small or industrial engine or a street or street/strip
car, none of us could come up with a  need for them, especially when there
were some issues with them.

Bill

> Hi: I'm a newbie to the list,and will ask a question that's probably
> been asked many times before.
>
> Anyone have good results with "Gapless" rings?
>
> John Culp wrote:
>
>> I dunno, I've put new rings in totally glazed old bores that weren't
>> hugely enlarged or out of round and had good results. The glazing
>> itself isn't a problem with gas sealing so much as it reduces the
>> oil-holding capacity of the cylinder wall and can cause problems with
>> ring and piston lubrication. A much bigger problem is if your bore is
>> worn till it's not round. The rings may have worn and turned as the
>> bore wore so they sealed fairly well in it, but new rings won't.
>> They'll bridge between high points across out-of round sections and
>> you'll get tremendous blowby.
>>
>> On pulling a piston out, I always look where the ring gaps are. In a
>> perfectly round bore with free rings (not pinned), there is no
>> preferred orientation and the rings will rotate randomly over time
>> running in the engine. The gaps won't be found oriented the same way
>> when you later pull the piston as when you put it in. (That's why
>> orienting them in specific ways isn't critical.) Often you find the
>> gaps all lined up on one side of the piston. That means the bore has
>> worn to an egg shape, with the gaps lined up on the pointy side of the
>> egg. That bore will have to be rebored.
>>
>> John
>>
>> On May 1, 2005, at 6:38 PM, peter ogborne wrote:
>>
>>> I just rebuilt a small single cylinder ,four cycle engine. .....short
>>> cuts ,don't take them ! Because i could not readily buy new rings i
>>> made some ,no problem there but i did not take the glaze off the
>>> bore. When reassembled there seemed to be lots of compression and
>>> start up was easy . After an hours run absolutely no
>>> compression...first thoughts it was the valves . I did the usual and
>>> shot some oil down the spark plug hole....compression !That
>>> eliminated the valves as the problem . Pulling the barrel off and
>>> examining the bore showed considerable glazing ,there was evidence of
>>> blow by ,oil coming out of the breather. So now it out with the hone
>>> ...................
>>
>>
>>
>> John Culp
>> Bristol, Tennessee, USA
>>
>> _______________________________________________
>> SEL mailing list
>> SEL at lists.stationary-engine.com
>> http://www.stationary-engine.com/mailman/listinfo/sel
>>
> _______________________________________________
> SEL mailing list
> SEL at lists.stationary-engine.com
> http://www.stationary-engine.com/mailman/listinfo/sel
>