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Re: question about piston rings... ??

To: <ptegler@gouldfo.com>, <triumphs@autox.team.net>,
Subject: Re: question about piston rings... ??
From: Barney Gaylord <barneymg@ntsource.com>
Date: Fri, 02 Nov 2001 20:30:03 -0600
At 08:33 AM 11/2/01 -0500, Paul Tegler <ptegler@gouldfo.com> wrote:
>When installing new rings on an old set of pistons....
>What are your thoughts on using one size over
>and using the proper tools to grind the proper
>end gap?   Are the normally supplied rings the
>properly sized?   If the bore is just a big larger than
>perfect, wouldn't an oversize ring allow the proper end gap
>to be set?

Yes, but, ....

1.  One piece rings .010" oversize could be used with a moderate amount of 
end grinding to achieve the correct ring gap.

2.  A three or 4 piece oil wiper ring would present a problem with 
shortening the butted ends of the ring spacer, as it is a formed part with 
turned up ends.  With the spacer end (or ends) removed it may not work right.

3.  If the bore is far enough oversize to be beyond the tolerance for the 
new rings, then it may also be out of round enough to cause problems with 
seating of the rings and walls for the break in period.  I have seen 
engines with badly worn cylinders honed and refreshed with new rings, only 
to have high oil consumption and still have some of the honing marks on the 
cylinder walls many thousands of miles later.

If the fresh rings have an end gap larger than the specs, then it's 
logically time for a rebore.  Of course if you're on a shoestring budget 
and don't intend to keep the car much longer or don't intend to drive it 
too many more miles, or you don't particularly care about the smoke and oil 
consumption, and you don't care about the loss of performance and possible 
piston slap, etc, etc, etc, then you could well do what you are 
suggesting.  After which I suppose we would soon be bidding you farewell 
from this list, as you would likely be losing interest or selling the car 
in the near future.  For the long term keeper cars there should be some 
concern for the long term proper repair.

$.02,

Barney Gaylord
1958 MGA with an attitude  (and a fresh rebore every 100,000 miles or so)
     http://www.ntsource.com/~barneymg

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