The Ford Barn

Frank Miller · 10-02-2015, 10:45 AM

A few years ago I asked this question and someone posted a link showing excessive end gaps in new rings did not adversely affect performance. the key was rings maintaining tension to seal against the cylinder. I can understand manufacturers wanting ring gaps off the thrust surfaces but as to where the gaps are in relation to the next should not make a difference. As pressure builds on top of one ring it increases pressure on the second through the gap. While the pressure will not increase instantaneously it is quick enough that 4 inches away should not matter. But let's look at the physical properties. If you have .030 end gap and ,010 piston clearance at the top it will give you .0003 sq inches for pressure to escape. And that is cold. Try putting an orifice that size on your compressor and see how much air escapes. Gapless rings might seem ideal but I'm wary they're creating a weak spot where the ring is thinner.

Bruce Lancaster · 10-02-2015, 11:54 AM

Interesting discussion...pretty obviously, the things go their own ways once the engine is fired, but manufacturers still specify placements at overhaul, some of them seemingly strange...Toyota above!
Ford '37-48 engine overhaul book, the Ford 1946 shop manual, and the good old '32-6 NAPA manual seem to ignore placement. Honest Charley gives very specific instructions (which I have had on file as long as I've owned a wrench), saying the main purpose is for break in.
So...why specific starting placements??

10-02-2015, 10:45 AM	#41
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	Re: Setting Piston Rings in Cylinders A few years ago I asked this question and someone posted a link showing excessive end gaps in new rings did not adversely affect performance. the key was rings maintaining tension to seal against the cylinder. I can understand manufacturers wanting ring gaps off the thrust surfaces but as to where the gaps are in relation to the next should not make a difference. As pressure builds on top of one ring it increases pressure on the second through the gap. While the pressure will not increase instantaneously it is quick enough that 4 inches away should not matter. But let's look at the physical properties. If you have .030 end gap and ,010 piston clearance at the top it will give you .0003 sq inches for pressure to escape. And that is cold. Try putting an orifice that size on your compressor and see how much air escapes. Gapless rings might seem ideal but I'm wary they're creating a weak spot where the ring is thinner. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

10-02-2015, 11:54 AM	#42
Bruce Lancaster Member Emeritus Join Date: May 2010 Location: Madison, NJ Posts: 5,230	Re: Setting Piston Rings in Cylinders Interesting discussion...pretty obviously, the things go their own ways once the engine is fired, but manufacturers still specify placements at overhaul, some of them seemingly strange...Toyota above! Ford '37-48 engine overhaul book, the Ford 1946 shop manual, and the good old '32-6 NAPA manual seem to ignore placement. Honest Charley gives very specific instructions (which I have had on file as long as I've owned a wrench), saying the main purpose is for break in. So...why specific starting placements??