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OldEvo 
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 Topic: Ring gap
Posted: 16 Feb 2021 at 11:59am |
Shown is a new ring in a cylinder of my '48 B. Bore is 3.379 with >.035 ring gap. Do I go with it or find some oversize rings and file to fit?
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OldEvo
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Posted: 16 Feb 2021 at 1:59pm |
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BTW, gap at the bottom is .027.
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Ed (Ont)
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Posted: 16 Feb 2021 at 2:52pm |
Seems like a lot. In my WD45 service manual it calls for piston ring end gap of .007 to .017. The piston is 4”. Some of the engine guys will let you know.
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steve(ill)
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Posted: 16 Feb 2021 at 4:09pm |
I rebuilt a car motor 30 years ago ... Bought .010 pistons and rings for it... DIDNT CHECK but the guy sent me standard rings in the box.. Ended up with a gap around .035 -.040 and it burn oil WAY TOO MUCH... I should have verified the rings before i installed.
You have .008 BIGGER gap at the top than bottom... divide by PIE ( 3.14) means the top is about .003 bigger diameter than the bottom.. You can get bigger rings and hone the bottom of the bore and FIT the rings to get .010 gap ( average).... problem is going to be the pistons are a little loose in the bore.... probably not a big deal on a 1600 rpm motor with 6:1 compression .......... personally i would get .010 bigger rings and gap them to .010 clearance.
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steve(ill)
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Posted: 16 Feb 2021 at 4:14pm |
Your bore is 3.379 instead of 3.375.... that .004 extra bore gives you .013 extra ring gap... Take that from .035 and those rings would have a .022 gap in a standard bore..... I assume the rings are right and your actual bore is probably 3.382 or so ??.. NOTE, if the gap at the bottom is .027 that is about .010 -.015 TOO BIG for new rings.. who made the rings ?
If the bore is actually 3.379 and you had standard rings set at .010 gap and you installed them in YOUR BORE, you would have +.013 extra gap or .023 total... i might use them in that case........ CLOSE, but still above spec.
Edited by steve(ill) - 16 Feb 2021 at 4:21pm
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OldEvo
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Posted: 16 Feb 2021 at 5:13pm |
Yep, the bore at the top ring at TDC is actually 3.379, carefully and repeatedly measured with fancy tools I am barely qualified to use. The bore at the top ring at BDC is a bit less but my notes aren't close by so I'm not sure by how much.
I wouldn't go so far as to assume the rings are right given their completely anonymous packaging. It's been a least five years since I bought them so it might be too late to return them.
Based on your experience with the oil burning rebuild I think I will try to find some rings for an .010 overbore and fit them to suit. Can you make any recommendations for a source?
Thanks for passing on some of your wealth of experience. Nothing beats having been there and done that.
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steve(ill)
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Posted: 16 Feb 2021 at 5:25pm |
Jeff, the problem i a m having is the numbers dont line up... If the BORE is .004 OVERSIZE then x 3.14 = about .012 or .013 EXTRA ring gap.... If you had STANDARD rings with a .010 gap and add +.013 you SHOULD be seeing .023 gap, not .035 ??
I think standard rings SHOULD give you that... But i agree, if you had rings that were for a 3.385 bore instead of 3.375 bore , you could grind the ends to get a GOOD GAP. Since you have .008 LESS clearance at the bottom, you might grind the rings to have .007 bottom and .015 at the top ??
I found a site that sells "RINGS" for boats and motorcycles that have 3.385 bore. At the bottom of the page it says " we have oil rings and scrapper rings to go with this... I would call them and tell them what your looking for.... and get the RIGHT THICKNESS of rings... I will post the link below..
Edited by steve(ill) - 16 Feb 2021 at 5:26pm
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steve(ill)
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Posted: 16 Feb 2021 at 5:38pm |
I have purchased rings from HASTINGS, but it was probably 10 years ago.. You might look at their site... They do list 3.386 bore rings. If you can find someone to talk to, this is your BEST BET.
https://www.hastingspistonrings.com/where-to-buy/
Edited by steve(ill) - 16 Feb 2021 at 5:42pm
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OldEvo
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Posted: 17 Feb 2021 at 10:54am |
I certainly agree with your numbers. Using pi rounded to four places 3.1416:
3.375 bore circumference = 10.603 3.379 bore circumference = 10.615 3.382 bore circumference = 10.625
So I'm confident with the numbers, my Mitutoyo micrometer and my measurements. I think the rings are just too short.
Thanks for the link to the Hasting site. They list two part numbers for this engine: 7762 and 2C7762 which has chrome top rings. Unfortunately only in STD size but it's a good reference point. I'm going to call some of the usual AC parts suppliers and see what they have.
Thanks
Jeff
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OldEvo
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Posted: 17 Feb 2021 at 10:59am |
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Also, the DLA parts look good. Thanks
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steve(ill)
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Posted: 17 Feb 2021 at 8:44pm |
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Hastings would make the rings, then grind the ends to correct size to get STANDARD... If you could buy a set BEFORE they grind the ends, you might gain a few thousandths on the gap by using standard rings.... Dont know if they would do anything like that or not... I have not seen .010 oversize rings listed for the ALLIS B-C motor.
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injpumpEd
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Posted: 18 Feb 2021 at 8:37am |
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I'd be more concerned about honing it straight again more so than the ring end gaps. A lot of people get hung up on that. Just having rings with some tension in this old 6:1 motor will make a huge difference. Hone out the taper, and put it together. Wipe out the cylinders with a clean rag and ATF, you'll be surprised how much grit you clean out.
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tbran
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Posted: 18 Feb 2021 at 9:07am |
Rule of thumb on Tractor engines is .004 X bore = correct end gap... higher the performance = wider the ring gap.
A rebuilt / re-bored / re-honed car engine is .0035 X bore = correct ring gap. Do it correct the first time or you will do it correctly the 2nd time - or someone else will have to. A non symmetrical bore will wear out the rings and lands much quicker....
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plummerscarin
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Posted: 18 Feb 2021 at 12:44pm |
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I wondered how long before someone pointed out the taper issue
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steve(ill)
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Posted: 18 Feb 2021 at 1:07pm |
told him that on day 1 ........... my problem was his numbers did not seem to line up with the given data..
You have .008 BIGGER gap at the top than bottom... divide by PIE ( 3.14) means the top is about .003 bigger diameter than the bottom.. You can get bigger rings and hone the bottom of the bore and FIT the rings to get .010 gap ( average)..
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plummerscarin
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Posted: 18 Feb 2021 at 2:35pm |
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Steve,
Not discounting what you said. Just seems the bore and taper are too far out of tolerance for a simple re-ring. Correct me if I’m wrong .
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steve(ill)
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Posted: 18 Feb 2021 at 4:25pm |
Im not sure.. I think it can be saved... My problem is the CYLINDER seems to be worn .004 at the top... that would give an EXTRA .012 ring gap... If the rings were STANDARD and had a .010 gap, then adding the .012 would give you a .022 gap in his cylinder.. He has a .035 gap ................ seems like the RINGS are not made correct ??
I know .022 gap is beyond speck, but i am incline to agree with ED.. A slightly high ring gap is not a show stopper.. HE could hone the BOTTOM of the liner to get things straight, then put GOOD STANDARD rings in and should have a .022 - .024 gap ?? I have done that on a couple B motors and had success.... I agree is it slightly out of spec, but it will work..... Might not do that on a D21 or my road Truck, but on a small B tractor, OK.... some BUDGETS do not allow for a rebore ( or new) , new pistons , new rings, etc...
If he COULD find rings that were slightly bigger and grind the gap, that would even be a better option..... but might be hard to find.
Edited by steve(ill) - 18 Feb 2021 at 4:31pm
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OldEvo
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Posted: 18 Feb 2021 at 6:49pm |
 steve(ill) wrote:
Hastings would make the rings, then grind the ends to correct size to get STANDARD... If you could buy a set BEFORE they grind the ends, you might gain a few thousandths on the gap by using standard rings.... Dont know if they would do anything like that or not... I have not seen .010 oversize rings listed for the ALLIS B-C motor. |
I searched the Hasting site and found a section where they sell single rings. Unfortunately they were only for high performance applications and none were the right size.
Yeah, I didn't find any .010 either. I talked to a couple vendors and the only stuff they had were 3-7/16 kits.
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OldEvo
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Posted: 18 Feb 2021 at 7:04pm |
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The tapered bore issue will be addressed once I figure out what my options are regarding rings. It's looking like a liner/piston kit may be the way to go. I don't see the sense in spending a lot of time honing the cylinders and then try to make a 3-7/16 ring kit fit properly.
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Ed (Ont)
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Posted: 19 Feb 2021 at 8:31am |
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I think that is your best bet. Do it once and will last a long time.
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OldEvo
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Posted: 19 Feb 2021 at 3:49pm |
Spent some quality time with my telescoping gauge and micrometer to get a handle on the taper issue. I took 30 measurements on each cylinder. One is tapered .003, one is .001 and the other two are .002. No problem there.
I think Steve's take on it is correct. The larger than spec ring gap is just not a show stopper. Still, I don't trust the no-name rings I currently have so I have ordered the Hastings 2C7762 ring set and will live with whatever ring gap I end up with.
Thanks to all
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jaybmiller
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Posted: 20 Feb 2021 at 6:51am |
Curious.... I was wondering what the cost of a liner/ring/piston 'kit' was compared to the machining cost to 'square the sleeve' would be ? Engine's already 'apart'... Jay
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DaveKamp
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Posted: 20 Feb 2021 at 8:38am |
OldEvo wrote:
Yep, the bore at the top ring at TDC is actually 3.379, carefully and repeatedly measured with fancy tools I am barely qualified to use. |
Jeff- don't EVER say you're 'barely qualified' to use measurement or mathematics, and ESPECIALLY not OBSERVATION.
Practical physics and an understanding of BASIC GEOMETRY empowers an individual to do amazing things with very little in equipment and prior training- it is the effectiveness of the processing space between your ears that matters!
While you might think the fancy tools are the most precise indicator, you're wrong- If you have a flashlight and a pair of eyes, you can shine a light down the side of a clean bore and SEE the taper. Take a piece of ordinary rule paper, fold it into a ruler small enough to fit at the bottom or top, and shine light at an angle, then look at the REFLECTION in the bore... then MOVE the angle of the light.
You'll SEE the reflected marks move, and you'll see that they don't all move the same- that is because the surface off of which reflection is occurring, is not consistent.
Optical measurement is using reflection and angle to magnify deviations in distance- it translates literally microns of deviation into abberations you can see with the naked eye.
Inserting that ring into the bore, and slipping a feeler gauge into the edge, has the potential to give you a more precise measurement than using a BORE gauge... because you have no centering error. Slipping a worn piston into the hole to SQUARE that ring, assures that you won't have error from being out-of-square.
That's why old timers always kept a worn out piston and ring on the shelf... it was their FAST MEASUREMENT KIT! ;-)
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