[SEL] Cylinder/piston update

[Michael Tucker]

Howdy all,

After all of the great info that I received from you folks, I thought 
that I would give you an update on what I found out yesterday.  You 
folks nailed it on the head with the space between the ring and the 
ring groove.  The gap with the first and second ring was 0.010 and 
the third ring was 0.060.  That's a far cry from the expected 0.001 
to 0.0015!  Also after getting the rings off I put the first ring in 
the cylinder to check the end gap.  The good news is that it made a 
nice tight fit in the bore and I couldn't get a 0.001 gauge between 
the ring and the cylinder at any point around the bore.  But the end 
gap was 0.073.  I'm pretty sure that's bigger than the ~0.018 that it 
should be for a 4.75" bore!  So, guess that new rings are on my 
shopping list.

After I got the piston all cleaned up I measured the size of the ring 
grooves.  At the very top of the first and second grooves, the width 
was 0.380 and from the middle of the groove to the bottom it was 
0.375.  In other words they have a bit of a "V" shape.  The first and 
second rings were only 0.369 wide (instead of 0.374) which accounts 
for the 0.010 space between the ring and groove.  The plan will be to 
turn the grooves straight to a width of 0.405 and install a 0.030 
spacer along with the new rings.  Hopefully that will take care of 
the compression problems.  If not I guess that I'll flame spray the 
piston to get it back up to specs.  Although after the great stepped 
piston sizing info that several of you folks sent that showed the 
correct gap between the piston and cylinder at the first, second, 
third ring lands and the skirt, it's not off by very much.  So I'm 
betting/hoping that the rings and ring groove work will take care of 
things.

Thanks for all of the great info folks.  This is the first time that 
I've really learned what the numbers on rings should be.  Before I've 
been able to get by with whether or not the rings "looked" good. 
It's the details that get ya'!

Thanks again,
Mike
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Michael Tucker
Midway, Kentucky, USA
mtucker at uky.edu
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