[SEL] Cylinder/piston questions

[R and E Freeman]

Do the rings have enough tension or spring left in them?Maybe the engine has 
got to hot in the past. Seems to me that if compression is lost suddenly as 
the piston changes direction its rings losing thier seal. If the rings where 
doing thier job and the piston is good size up to the ring gaps the piston 
should not wobble? Just food for thought anyway.

Ray Freeman

Portable Line Boring
http://www.plb.iinet.net.au
plb at plb.iinet.net.au
----- Original Message ----- 
From: "Michael Tucker" <mtucker at uky.edu>
To: "The SEL email discussion list" <sel at lists.stationary-engine.com>
Sent: Monday, May 23, 2005 6:45 PM
Subject: Re: [SEL] Cylinder/piston questions


> Howdy all,
>
>>I agree with a prior comment that the ring gap and fit is more critical 
>>than the fact that you may have an undersize in the piston between the 
>>grooves.
>
> The rings fit very nicely in the ring groove and although I haven't 
> measured it, the gap looks pretty good as well, especially since the rings 
> have overlapping ends.  I'm sure that new rings and oil will help but the 
> thing that bothers me about the compression loss is that it's not a 
> constant loss as the piston comes up on TDC.  Instead, is looses some 
> compression as it approaches TDC but just as it goes over TDC and the rod 
> goes from pushing to pulling, what compression there is lost all at one 
> time in sort of a loud pop.  This makes me think that the piston is moving 
> around a little too much.  In fact with the head off, you could see the 
> piston wiggle a little bit as it rolled over TDC.  That's what worried me 
> that the cylinder was out of round. Although it is out of round just a 
> bit, from the measurements I think that most of the wiggle is due to the 
> piston wear and not the cylinder.
>
>>If you want a more perfect fit on the piston, have it flame sprayed and 
>>turned down to 5 to 6 thousandths less than your bore.  Do this and put in 
>>new rings  and your hunk of iron should need a compression release to turn 
>>it over.
>
> From y'alls comments on how much clearance there should be, flame spraying 
> is where I think I'm heading with this critter.  Since I intend to work 
> this engine on a buzz saw rig rather that just running it, I think that I 
> need better compression than it has with its built in compression release 
> at TDC!.  I'll definitely hone the cylinder as well as replace the rings 
> and like you say, it should have compression to spare!  Tommy, do you know 
> of any places here in the Bluegrass that do flame spraying?  What type of 
> metal compound should be applied for ability to machine and good wearing 
> properties?
>
> Thanks for the help folks,
> Mike
> -- 
> ____________________
> Michael Tucker
> Midway, Kentucky, USA
> mtucker at uky.edu
> ____________________
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