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I Made A Mistake

S

skycarp

Member
Hi Guys,

I am rebuilding a C-123 engine (Farmall Super C). I have a complete engine rebuild kit with sleeves, pistons, rings etc. which came with an 1/8 inch overbore. I am now at the reassembly stage and I think I really messed up on the rings. I read the specification pages wrong.

The end gap on the top ring[b:0b204d7ff2] SHOULD[/b:0b204d7ff2] be .010 - .020 inch. I read the specifications for ring to grove clearance, which is .035 - .055, by mistake and used that specification for the ring end gap. I took the end gap on the all four top compression rings to .035 inch before I discovered my error. The second and third compression rings are at .020, as specified.

1. Will I see a noticeable loss of compression on this new engine?

2. If so, will it be enough to effect the power of this engine?

3. Will the compression fall off even more as the engine breaks in?

Thanks in advance,

Dean
 
New rings amd pistons in a kit are ready to install with out doing any altering of the rings. Damage is done only othere thing to do would be order new rings from the same supplier. In the many years of installing kits i have always installed the rings that came with the kit without any further measuring. Run the engine and good luck
 
If you are worried about it and you will think of it everytime you start the engine, just go buy another set of rings. It will be much easier to change them now, rather than when you have everything together and then decide you should have done it.
 
I'll second that... buy another set of the same rings. You will always be thinking about it if you don't. ..ag
 
My gut reaction from limited experience is that with 4 rings, it probably won't affect it that much. At least rotate it to the opposite side of the second one. I'm enough of a perfectionist that I'd probably buy new rings depending upon the price. Kinda also depends on if it is a racing engine or a parade tractor engine or a mowing tractor.
 
I agree that a new set is the best option. It will be mediocre to find that after 100 hrs that it has blowby and smokes. I also believe that the rings can be found many places, and that high quality is most important.
Rings must be far tighter in the ring to groove than that specification cited in your post!
Possibly ring diametral thickness to bottom of groove, but not under or over ring. It would make noise like mowing bolts.
Jim
 
New piston ring end gap should be .003-.004" per 1" of cylinder diameter. So with a 3" diameter cylinder, .009-.012" would be the minimum for new installation.
Side clearance for ring to groove should be .0035-.0055", not .035-.055" as you stated.
That much clearance would really rattle the ring in the groove!!! Plus there would be a lot of oil consumption.
Please read the instructions very carefully FIRST.
 

Jim and others,

Thanks for the comments and information. In looking at the I & T manual, I see the allowable side clearance for the compression ring is 0.001 - 0.0025, not .035. This doesn't effect me as I have new pistons and rings, but is is important to make corrections of any incorrect statements so that others won't make a mistake as a result of the erroneous statements.

I got the information on side clearance from the original service manual, which I do not have here at home now to check my earlier statement. But you are correct in the side clearance information.

I will try to find a set of top compression rings, or reorder a complete new set. A complete set of rings will cost me $44.00 plus shipping so this is a costly mistake.

Dean
 

Jim and others,

Thanks for the comments and information. In looking at the I & T manual, I see the allowable side clearance for the compression ring is 0.001 - 0.0025, not .035. This doesn't effect me as I have new pistons and rings, but is is important to make corrections of any incorrect statements so that others won't make a mistake as a result of the erroneous statements.

I got the information on side clearance from the original service manual, which I do not have here at home now to check my earlier statement. But you are correct in the side clearance information.

I will try to find a set of top compression rings, or reorder a complete new set. A complete set of rings will cost me $44.00 plus shipping so this is a costly mistake.

Dean[/quote]

Actually, $44.00 is kind of a tough pill to swallow, but we ALL have made mistakes that cost us a whole lot more than $44. Chalk it up to experience and don't worry about it.
 
If it's only a $44 mistake, he got off cheap IMHO.

Remember that $44 doesn't go nearly as far as it used to.
 
Dean, Are you doing this engine rebuild on the fast hitch Super C you restored a few years ago which you found in Idaho? Nice to see you on the Farmall forum again and hope all is going well. I finally got my Super C's restoration finished this past winter after working on it for close to four years along with the other disruptions I've had. Shoot me an email if you have a few moments as my email is open, Hal.
 
What you did by enlarging the end gap of the top ring is exactly what IH did with the 400 series engines to get longer life out of the sleeves and pistons. The idea is to put more load on the second ring to even out the wear. In your case it may cause a little more blow by but it will not substantially affect the life of the rebuild. It might even help the engine life by evening out the wear.
 
I think you made a wise choice to intall a new set of rings. We all mess up once in awhile. It will give you peace of mind too. Hal
 
You are indeed taking the correct path in getting new rings, but it might be worth checking on getting just the ones you need- but $44 for a set ain't bad. Any good speed/ machine shop counter guy can find oddball ring stuff- many times we'll find available ring sets and have custom pistons made in that bore size to save a rare block. Checking the ring end gaps is part of the dilligence of any good engine build, not wasted time- if you want it right, do it right. Sometimes the stuff in the box ain't the right stuff LOL. On the hot rod/ race stuff we always use .005 over rings that a made to be hand-fitted, considered SOP on a "next level" build. There's also spacers available to correct ring to groove clearance, both side clearance and back clearance
 
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