[SEL] piston rings

curt at rustyiron.com curt at rustyiron.com
Tue Apr 28 12:59:14 PDT 2009


Arnie,
When wiring the rings closed there is no gap. Turn the OD to the cylinder
diameter. Then remove from the fixture. I surface ground them to get the
desired width, making them .0005 to .001 narrower than the ring groove.
Just before sliding the rings on, I file the desired gap. I actually do a
modified step gap, cutting the gap only 1/2 way across the ring width on
one side, and the opposite on the other side. Did that make sense?
If you buy step gap piston rings there is considerable overlap when the
ring is installed in the bore.
On the modified step gap, there is no overlap when the ring and bore are
at the same temperature. As the ring temp exceeds the bore temp it grows
and the stepped halves begin to overlap slightly, essentially making for
an air tight gap.
Probably not a big difference over the traditional gaping method across
the full width of the ring, but I figured it couldn't hurt. I've done 3
engines this way now, including the Alamo and they have loads of
compression and run nice and slow.
Curt








> Curt,
>
> I'd forgotten about that webpage.  VERY nice tutorial.  That's one that
> even I could
> follow.  8-))
>
> One question...
>
> Do you set any sort of end gap in the rings when you turn the OD or do you
> include
> that gap when you determine what final OD you want when the ring is in the
> cylinder
> bore?
>
> See ya,  Arnie
>
>> The traditional method is to cut an over sized ring of the correct
>> dimensions, remove a section, compress the ring to a collapsed diameter
>> (now oval shaped), mount the compressed ring in a turning fixture and
>> then
>> turn the OD to exactly the cylinder diameter. This is the method used by
>> folks like Niagara Piston Ring.
>>
>> I took photos as I was doing this last summer and placed it on my
>> website.
>> Here is the link.
>> http://www.oldengine.org/members/holland/images/MakingPistonRings/Thumbnails.html
>
>
>
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