Piston rings

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islecastle
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Piston rings

Post by islecastle »

I'm going to have to do a piston ring job on my 1098.
Any reccomendations positive or negative?
I see that Cords rings are still available. What about Oilmasters?
Until I've pulled them, I'm assuming that the pistons are OK.
Dave
oliver90owner
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Re: Piston rings

Post by oliver90owner »

If using solid rings, check the side clearance in the piston ring grooves (particularly the top ring). If out of spec, it is likely to pump oil.

Check bore for a lip at TDC for the top ring. If present, remove or fit stepped rings.

Don’t assume anything. If bores are oval, the new rings likely won’t bed in. Check ring gap in worn portion of bore and at an unworn section to gauge bore wear, if bore measuring micrometers are not available.

What condition is the bottom end? New parts, and effort, can be wasted if the job needs a crank re-grind.

Have fun and don’t cut corners if you can avoid it.
islecastle
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Re: Piston rings

Post by islecastle »

Thanks Oliver. Sound advice I think.

Re the bottom end, if the big end shells and journals are in good condition, would you replace the shells anyway?
Dave
oliver90owner
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Re: Piston rings

Post by oliver90owner »

For the cost of a set of bearings, is it worth it?

Most wear is likely on the centre main bearing.
islecastle
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Re: Piston rings

Post by islecastle »

Received a set of rings from ESM this morning.
The third ring down has a 'top' marking on it and when fitted it has a ridge dodger at the bottom. Strange?
The top ring has no ridge dodger.
I queried this with ESM, and he examined another packet of rings and confirmed that they were the same.
Any comments?

Dave.
paul 300358
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Re: Piston rings

Post by paul 300358 »

I don't know what make of rings you have but the top ring usually has a centre dot to mark which face is up. Also its usually the second ring which has a lip[attachment=0]
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islecastle
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Re: Piston rings

Post by islecastle »

Mine are different, and there are 4 of them.
philthehill
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Re: Piston rings

Post by philthehill »

The lip dodging piston ring is normally fitted as the top ring with the cut out facing the top of the bore.
It has to be the top ring as that is where the wear lip is located. put the lip dodging piston ring anywhere else and it is not doing its job and the ring in the top groove without the cut out will in all probability break as the top outer edge hits the wear lip at the top of the bore.
The majority of pistons rings when new are marked with a dot or a 'T' which should be placed upwards.
Piston ring schematic 3.jpg
Piston ring schematic 3.jpg (325.83 KiB) Viewed 143 times

islecastle
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Re: Piston rings

Post by islecastle »

The rings that ESM sold me are completely different.
I couldn't find any others, but if anybody knows where I can get some I would be much obliged.
philthehill
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Re: Piston rings

Post by philthehill »

Looking at the piston rings posted for sale on the ESM web site they seem to be standard fitment.
What is actually different that is causing concerns?
A close up photo of the rings you received from ESM & posted on here would be of help in determining what if anything is wrong.
https://www.morrisminorspares.com/engin ... -4-p830124
https://www.morrisminorspares.com/engin ... e-p1238290
Do you have an oil control ring below the gudgen pin?

islecastle
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Re: Piston rings

Post by islecastle »

The ring set that I got off Esm this morning has their part no. 10M123S.
According to the manufacturers, unmarked rings can be fitted either way up.
The top ring is plain and paralell sided with no ridge dodger or chamfers. Unmarked for orientation.
Second ring the same.
Third ring is marked for top and has ridge dodger at the bottom.
Oil control ring is 3 part. 2 thin rings either side of a castellated thing. There is precious little spring in it.
Manufacturer is Hastings Manufacturing Company USA.
No ring below the gudgeon pin. Your link is to the 5 ring type.

I think I will be searching for another set.
philthehill
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Re: Piston rings

Post by philthehill »

Thank you for the additional information.
https://www.morrisminorspares.com/engin ... pe-p830313
Did you not get any fitting instructions with the rings?
The castellated ring is not supposed to have any spring in it - it is just there to keep the oil control rings apart. The oil control rings do not have much spring either - they just scrape the oil off the bore wall and direct it down through the cut outs in the piston and back to the sump.
All the ridge dodger rings I have come across all have the top ring top outer edge cut away to ensure that the ring does not come into contact with the wear ridge at the top of the bore.
I am just playing around with some Triumph 1500 pistons and rings with the intention of fitting them into a 'A' Series and fitment of those rings are as I describe above.
Counting the number of ring parts I am of the opinion that 10M123S ring set is for a 5 ring piston.
You have a top ring x 4 , a 2nd ring x 4, a 3rd ring x 4, a 4th ring x 4. Then you have the octagonal ring x 4 which fits into the bottom of the scraper ring groove (this pushes the castellated ring outwards), then you have the castellated ring x 4 which fits around the octagonal ring, above the castellated ring you have a thin scraper ring x 4, below the castellated ring you have a thin scraper ring x 4.
Which gives a total parts number of 32 items which corresponds to the number of ring parts in the link above.
Irrespective of the way items are marked or laid out I believe that you have the wrong piston ring set and possibly the wrong fitting instructions.

islecastle
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Re: Piston rings

Post by islecastle »

Thanks for your input here Phil, and the others. Although the rings fit well enough, I am a bit perturbed about the deviations from the standard as in your diagram. I can't see the oil rings doing much good which defeats the object of doing the job in the first place!
The bores are standard and I can't feel any wear ridge.
I've found a piston ring supplier, Thorntons, and left an enquiry. I'll post up if they look promising.

Dave
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Re: Piston rings

Post by oliver90owner »

Although the rings fit well enough

I’m not sure that is actually true. You may think so, but there is precious little information for us to recommend simply fitting new rings to your engine.

What findings, from my first reply, indicate re-ringing is going to be worthwhile?

In my time, I have re-rung a lot of old pistons. Some have been where new pistons are simply not available. Some have required remedial attention to the piston(s). Some have been fitted to worn bores (with worn pistons - again, where no spare parts were available).

I’ve even fitted home-made rings.

I don’t particularly like re-ringing anything that revs beyond a couple thousand rpm unless everything is within spec. Put simply, from my experience, the ‘repair’ does not last very long, if not done properly.

I’ve even been asked about repairs, such as this, where the cause of blue smoke had little to do with the piston rings.

There is likely more to this job than just fitting new rings, so (without more info being forthcoming), I’ll keep out of further discussions on this one.
islecastle
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Re: Piston rings

Post by islecastle »

Thanks Oliver.
Points taken.
Going any further than a reringing job really means a complete engine ovehaul. Oh, and while I'm at it a new clutch and having gone that far, a recon gearbox and back axle. And so it goes on.
Anyway I've ordered a set of Cords rngs. I've used these in the past on an A40 Farina and Peugeot/Ford 2.5 diesel.
I'll report back success or failure.
Dave
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Re: Piston rings

Post by King Kenny »

I did an engine refurb some time in the 90s. I replaced the bearings and fitted Cord piston rings. I am still running the same engine with no problems.
1969 Traveller in Almond green. Owned since 1979.
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