Piston Ring End Gap

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outdoors4evr
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Zip Code: 48423
Tractors Owned: 184
Location: Davison, MI

Piston Ring End Gap

Postby outdoors4evr » Fri Jan 06, 2017 7:12 am

I noticed my 184 was starting to "breathe" quite a bit through the dipstick (crankcase breather) so I decided to dig into it over the Christmas Holiday. When I pulled each piston, I found some of the ring gaps were only offset by 90 degrees rather than the recommended 180 degrees. The rings were not tight in the piston and could be rotated by hand. There isn't really a way to keep the rings from walking so I don't think there is a good way to solve this issue other than putting the rings back in properly and hoping they don't move or if they do move, at least move together.

I then popped each ring out of the piston and put it in the bore 1/2 way down and measured the end gap. Each ring gap measured between .020" and .025" (20 - 25 thousandths of an inch) I didn't find a specification on this in the service manual, but did find a minimum gap specification of .006" (6 thousandths of an inch) in the paperwork that came with the new rings.

The rings I removed were .020" over so I purchased .030" over rings and filed each them to fit the suggested minimum in the new rings paperwork. I don't have a lot of hours on this tractor since last bored (300 hours) so I just measured the cylinders which are still round and have no ridge at the top. I didn't bother to hone as there is no scoring or issues to address.

Any thoughts on ring end gap minimum and maximum tolerances??? Did I make these too tight for the aluminum dome top (pop up) pistons?
I'll break it in gently and change the oil again before the mowing season. It does run well again and the dipstick is no longer being fogged with oil.
184 w/ Creeper & 3-Point
IH 3160a Mower
IH Model 15 Tiller

Eugene
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Re: Piston Ring End Gap

Postby Eugene » Fri Jan 06, 2017 7:39 am

.007 minimum. .017 maximum. Probably for cast iron pistons. Aluminum pistons may have a slightly different ring end gap range.

Not sure why an engine with 300 hours since rebuild would have a ring end gap of .020 to .025.
I have an excuse. CRS.

Mike H
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1972 SS12 retro fitted
1977 F150 pull truck
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Re: Piston Ring End Gap

Postby Mike H » Fri Jan 06, 2017 9:34 am

end gap is critical . in general too much ya get blow by too little ya start breaking pistons as the engine warms up.
the rings need to move freely so they don't break the skirting off of the pistons.

Mike

outdoors4evr
5+ Years
5+ Years
Posts: 1024
Joined: Tue Jul 22, 2008 12:44 pm
Zip Code: 48423
Tractors Owned: 184
Location: Davison, MI

Re: Piston Ring End Gap

Postby outdoors4evr » Fri Jan 06, 2017 3:07 pm

Not sure why an engine with 300 hours since rebuild would have a ring end gap of .020 to .025.


Simple: The new guy putting it together the first time (me) didn't know any better. Don't put .020 over rings in a .030 over bore.
184 w/ Creeper & 3-Point
IH 3160a Mower
IH Model 15 Tiller

Eugene
Team Cub Mentor
Team Cub Mentor
Posts: 15283
Joined: Fri Jul 02, 2004 9:52 pm
Zip Code: 65051
Circle of Safety: Y
Location: Mo. Linn

Re: Piston Ring End Gap

Postby Eugene » Fri Jan 06, 2017 3:48 pm

outdoors4evr wrote:Simple: The new guy putting it together the first time (me) didn't know any better.
Since you have the pistons out. One at a time, Plastigage a main bearing/journal, then reinstall the bearing cap. Then move on to next main bearing. During piston assembly, Plasitgage each rod bearing/journal.
I have an excuse. CRS.


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