Has anyone used just the top three piston rings on 9N 4 ring pistons?

mi 2 cents
Might be a good idea for more RPM on that race car, A small amount of oil burn might be worth it but then the question becomes one of how much oil goes into the cylinder potentially reducing power. However being as this is a race car engine a few laps around the track should be worth the risk.
Ooops. Wait. This isn't a race car. Being the 4th ring is another oil control ring that is supposed to last the next 50 years, it might be worth putting in.
That is unless your planning on more mission creep in the future.

Hi Bruce,
Just questioning the need as the 8N only uses the top three and the pistons are identical to the 9N except for that lower ring, so thinking it is probably not really needed. Cost for the set of four is more than for the three set.

That 4th ring being oil control. Beyond that, is the 3 ring piston a different set up on oil control rings or the same? Piston ring width/top gap/end gap from 3 to 4 piston? Me? If I desired a 3 ring set up, would go with the 3 ring piston.

If it all checks out, then going with a lack of a 4th ring should not hurt anything.

I suspect it will be different because Ford would not add anything that was not needed.
Cost difference from 3 to 4 is how much? Times 1,000,000,000 tractors is how much?
So from a manufacturing standpoint, why add something to a machine that is not needed?

I figure that in designing the 8N they considered the 4th ring not necessary and eliminating 25% of the friction and machining the groove was worth it. Lands and grooves and skirt length are the same. Not sure if an open groove puts much additional oil on the walls and possibly ups oil usage. Someone in one of the forums said they had used three rings on a four groove piston, but did not say anything further.

I suspect you are right, Steve. I've been looking at my library of dealer technical bulletins and I don't have one that specifically mentions why Ford dropped the 4th ring, but there are a few that document the continued evolvement of piston rings on the 8N, so it would appear that they were a work in process.

'bout time you showed up.
I have been swinging in the dark. Henry not wanting to spend a dime more than needed might have initially gone to a 3 ring set up and then finally changed it to a 3 ring piston.

Well with this discussion of lands and grooves I decided to actually measure the grooves on each piston and they are different!!! So I started researching rings sizes and there are about 8 different piston manufacturers and several different groove combinations. The 8N pistons top two were .0093 and the third groove is 0.1875. The top and second rings on my 9N pistons are 0.116 and 0.099 respectively and third is 0.156 as is the forth. Just 8N's doesn't detail the sizes in it's set of four rings, Yesterday's tractors has 2 top at .093 and the last two as 01875. Others have 5/32 and 3/16 combos, etc. Finding the correct set for my pistons is going to be a real chore. May have to scrap these 9N units and get new ones.

Someone in this club might want to do a detailed article on the evolution of the pistons and rings for the 9, 2, and 8N engines.

LOL.....I thought that I had seen a TSB in the past that addressed the change, but no cigar. This is one from 1950 that addresses excessive oil consumption complaints from customers and may be related to the reduction in rings.

It's been too long since I looked at a 4 ring piston. I am at a loss for the 3rd and 4th oil control rings being the same design as the 3 ring piston, oil control ring.
Well Steve, your research only helped to confirm my suspicions regarding side ring gap.
Hope you get it dialed in for a long term solution.

The pistons I have that I removed from two 9N's are both 4-ring units and the top and second compression rings are 3/32" while both oil rings are 5/32", (0.093 and 0.156 respectively. The three ring 8N pistons are 3/32 compression (2 ea.) and one 3/16 oil ring (.187). Entering into this discussion I was planning on using one set of the 9N pistons which looked in almost perfect condition, however when I decided to gather some factual data, brought on by your comments, I found the grooves to be far over spec. 0.115 top, 0.108 second and 0.164 for the bottom oil rings. So now I pulled out my old set of 8N three ring pistons that I removed from that engine about six years ago and looked them over and checked the grooves and they are w/i spec. I took them over to my machine shop and they checked good on diameter and his view was the slight visual scoring wear would not be a problem-so looks like I'll probably use them. New ones from Just 8N's are $45 each (were $20 when I rebuilt the 8N) so adding tax and shipping I'd be well over $200 that may be unnecessary for this engine.

If we had not had this back and forth I might well have spent $130 for a set of rings that would have gone on out of spec pistons before I realized the problem.