piston ring end gap spacing ?

[old ugly]

i have always spaced the end gaps of the piston rings about 120d apart and not over the pin.
but
is there a chart or spec on the actual recommended spacing?

thank you
ou

[Gary WA]

If you have Les Andrews Model A Mechanic book specs in there.

[40 Deluxe]

It makes absolutely no difference where the compression ring gaps are located! None! Rings randomly rotate in their grooves as the engine runs so they will at times be lined up. Guess what! Your engine starts and runs the same as always!
The only concern is that the oil ring rail gaps be offset on either side of the expander gap to facilitate installation.
We only stagger the compression ring gaps to honor an urban legend (old wives' tale, formerly).
Piston diameter in the ring land area is much smaller than the bore (to allow for expansion) so there is a lot of space for oil and/or compression blowby to travel from one ring gap to the other, while the ring gap itself is quite small. So the relative locations of the gaps is meaningless, no matter what old timers and "armchair experts" claim!

[katy]

Originally Posted by old ugly

I have always spaced the end gaps of the piston rings about 120d apart

Please explain "120d"

[old ugly]

les andrews says 120d apart. its all i have been doing for years so i will just carry on as if i were normal.
thanks
ou

[old ugly]

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Originally Posted by katy

Please explain "120d"

i don't know how to make the little degrees sign.

[katy]

Originally Posted by old ugly

i don't know how to make the little degrees sign.

Hold down the alt key, type 2 4 8 on the right hand number pad, gives °

Do a search for alternate characters, lots of info available

[Jemelton#]

Originally Posted by katy

Hold down the alt key, type 2 4 8 on the right hand number pad, gives °

Do a search for alternate characters, lots of info available

Thanks for the tip! Now I know what to do!

[Bob Bidonde]

May be this will help:

[Y-Blockhead]

Originally Posted by katy

Hold down the alt key, type 2 4 8 on the right hand number pad, gives °

Do a search for alternate characters, lots of info available

Or option, shift, 8 = ° on a Mac.

[Patrick L.]

120°

[BRENT in 10-uh-C]

Originally Posted by 40 Deluxe

It makes absolutely no difference where the compression ring gaps are located! None! Rings randomly rotate in their grooves as the engine runs so they will at times be lined up. Guess what! Your engine starts and runs the same as always!
The only concern is that the oil ring rail gaps be offset on either side of the expander gap to facilitate installation.
We only stagger the compression ring gaps to honor an urban legend (old wives' tale, formerly).
Piston diameter in the ring land area is much smaller than the bore (to allow for expansion) so there is a lot of space for oil and/or compression blowby to travel from one ring gap to the other, while the ring gap itself is quite small. So the relative locations of the gaps is meaningless, no matter what old timers and "armchair experts" claim!

I do agree with you 110% regarding the ring installation and gap alignment does not matter however most do not realize that if the rings are rotating randomly, this generally indicates a different issue which most of the time is a bent connecting rod. A bent rod will cause the piston to twist in the bore as it travels vertically in that bore. It is that twisting that can cause the ring to rotate. Otherwise the ring has the same contact 358° of the bore and nothing to push it into rotation.

[Patrick L.]

Rings can rotate in the bores, in theory. I find that they don't.

[40 Deluxe]

Originally Posted by Patrick L.

Rings can rotate in the bores, in theory. I find that they don't.

If rings did not rotate in the bore, there would be a tiny unworn area at the top of the bore where the top ring gap was. Have you ever torn down a worn out engine with this unworn spot? In 60+ years of doing engine work I never have!

[40 Deluxe]

Originally Posted by BRENT in 10-uh-C

I do agree with you 110% regarding the ring installation and gap alignment does not matter however most do not realize that if the rings are rotating randomly, this generally indicates a different issue which most of the time is a bent connecting rod. A bent rod will cause the piston to twist in the bore as it travels vertically in that bore. It is that twisting that can cause the ring to rotate. Otherwise the ring has the same contact 358° of the bore and nothing to push it into rotation.

Have you ever seen an engine with a tiny unworn spot at the top of the cylinder indicating the ring never rotated? I never have!

[old ugly]

Originally Posted by Bob Bidonde

May be this will help:

i was talking about the end gap spacing, the angle/position when installed onto the piston.
thank you

[old ugly]

Originally Posted by katy

Hold down the alt key, type 2 4 8 on the right hand number pad, gives °

Do a search for alternate characters, lots of info available

haha
i tried all the suggested functions to make that little o. it don't work on my keyboard.
thanks tho

ou

[Patrick L.]

Originally Posted by 40 Deluxe

If rings did not rotate in the bore, there would be a tiny unworn area at the top of the bore where the top ring gap was. Have you ever torn down a worn out engine with this unworn spot? In 60+ years of doing engine work I never have!

I have, but, always because of a broken ring.


There shouldn't be a wear spot at the open end of a ring if the ring has been filed correctly. The other rings work/wear on the wall in that location.
Rings do move around, but, its not as if they rotate consistently.

Some pistons are pinned as to not allow rings to move at all.

[BRENT in 10-uh-C]

Originally Posted by 40 Deluxe

Have you ever seen an engine with a tiny unworn spot at the top of the cylinder indicating the ring never rotated? I never have!

To answer your question, ...yes, but again most rings today are gapless so it is moot.

FWIW, we monitor high-performance engines closely during assembly and then in teardown. The ring gaps are noted where they were installed and where they come out. They generally do not move, and usually it is because the piston was inserted and twisted as the rod was connected to the pin.

So going the other direction, what causes the ring to rotate?? Compression pressures are not going to rotate it, and if the piston is moving in a straight line within the bore, unless the rod is rotating the piston slightly during the cycle, tell me what is moving them??

[40 Deluxe]

Originally Posted by Patrick L.

I have, but, always because of a broken ring.


The other rings work/wear on the wall in that location.

But the other rings do not reach the top of the cylinder so can't "work/wear that location".