[SEL] Cylinder/piston questions

[peter ogborne]

Mike ...I have been making some piston rings . What i have found that 
although the ring gap was acceptable the ring clearance in the piston groove 
was far excessive ,hence my blow by. New rings with minimum groove clearance 
plus a de glaze with a hone, result perfect compression.
----- Original Message ----- 
From: "R and E Freeman" <plb at iinet.net.au>
To: "The SEL email discussion list" <sel at lists.stationary-engine.com>
Sent: Monday, May 23, 2005 10:01 AM
Subject: Re: [SEL] Cylinder/piston questions


> Mike , looks like you have a worn piston but I'm not sure if it would make 
> all that much difference to the blowby. Lots of people here would know 
> more about that than me but I would think if the rings are OK and a good 
> fit in the ring grooves it should seal up with some oil around there. Your 
> smallest bore measurement and largest piston measurement would be close to 
> unworn sizes so it was originally around 8 thou clearance. Modern engines 
> would be tighter but in that I would think 6 to 8 thou would be OK
>
> 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 8:49 AM
> Subject: [SEL] Cylinder/piston questions
>
>
>> Howdy all,
>>
>> I was able to start evaluating the mechanical status of my new toy today. 
>> It's a 1907 (serial number R1434E) 4 hp, screen cooled, hit-n-miss IHC 
>> Famous.  Although the rings were essentially dry, when pulling it through 
>> compression it seemed to be loosing a lot of compression past the piston 
>> at top dead center.  So, with the help of my machinist neighbors tools I 
>> took some measurements of the piston and cylinder.  The cylinder is in 
>> great condition with no hint of a ring ridge.  Up at the head end of the 
>> cylinder the horizontal diameter is 4.8025" and the vertical diameter is 
>> 4.8060".  At the flywheel end of the cylinder the horizontal diameter is 
>> 4.8010" and the vertical diameter is 4.8035".  So, there is a tiny taper 
>> and the cylinder at top dead center is only 3.5 thousandths out of round. 
>> I think that I should be VERY happy with those measurements.  The piston 
>> is what I'm a little worried about.  Although it is absolutely round up 
>> by the rings and at the end of the skirt, between the first and second 
>> ring the diameter is 4.780" and at the end of the skirt, it's 4.794".  So 
>> at the top of the piston, that gives me a vertical difference in the 
>> diameter of the piston and cylinder of 26 thousandths and a horizontal 
>> difference of 22.5 thousandths.  In a perfect world, what should the 
>> difference in piston diameter and cylinder diameter be?  Although the 
>> rings look to be in pretty good shape, do you think that they could be 
>> the reason for the blowby?
>>
>> Thanks for the help,
>> Mike
>> -- 
>> ____________________
>> Michael Tucker
>> Midway, Kentucky, USA
>> mtucker at uky.edu
>> ____________________
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