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I'm rebuilding a 1275 S motor with original BMC AEG341 pistons. The bores are at +0.020". According to the Minispares catalogue and the Somerford Mini website I need a set of rings sold under part number BHM1165020. These ring sets are supposed to have 1.19mm thick compression rings and a 4mm oil ring.

I ordered said set of rings from Somerford (Minispares says they don't have them or don't know what I'm talking about). The rings arrived on Friday and are a set made by Cords. The top ring is 1.17mm, the second and third rings are each made up of two thin rings that are presumably spaced so there is no gap. Combined width of these two bits that make up one ring is 1.04mm.

Now my intuition tells me my mechanic is going to laugh at me and throw these expensive rings in the bin. But I don't have a lot of experience, so I'm hoping someone on here can shed light on these gapless rings and why they are much much thinner than what the ring land can take.

Please help. The motor is supposed to go back together tomorrow but I fear it will have to be postponed.

The thin Cord rings are made of steel rather than cast iron, and are used in pairs in each ring groove.

They were (are?) meant to be better at controlling oil consumption.

Pretty sure you can still get these 'S' width rings in cast iron from Deves or Goetze.

Coard rings were all the rage in the seventies when I worked for a BMC Layland garage they were to help with high oil consumption with the thin rings there should be some thin wire cords that go in the ring gap as well didn't know they still made them work well if fitted correctly.

Thanks for the replies so far.

So should I be worried that the combined width of the two piece ring in #2 land (and same in #3) is much less than 1.19mm? These two piece rings didn't come with any thin wire cords.

abri wrote: So should I be worried that the combined width of the two piece ring in #2 land (and same in #3) is much less than 1.19mm? These two piece rings didn't come with any thin wire cords.

Short answer yes. They do not work without the wires (if they ever did with them...) and the 'float' in the groove will wear the ring lands faster than you can say drat.

Cords rings in my experience were a solution looking for a problem that was much more easily solved with correct machining and honing.

I have fitted several sets in peoples engines, mostly in the 80's and they do work initially (compression goes up, oil consumption down) but after a few thousand (in one case a few hundred) the engines were back to where they started or worse.

Personally I would not fit them and get some of the correct parts.

Just my 2 cents.

Grant and Hastings (for 2 manufacturers) have correct rings available for the original pistons. They are fairly priced and good quality. Plain Iron or Chrome Faced available. I'm sure I'd have at least 3 or 4 sets in the draw.

Thanks for the replies. The Cords rings will be returned to Somerford.

I have been scouring the web for the correct rings without much luck. If anyone can refer me to the correct part number or even to a supplier, I'd be most appreciative. I believe I'm looking for the set with a Hepolite part number of R19520-20 or a Grant part number C1715. This is proving a lot harder than I thought!

Try Thorntons at Wellington Shropshire 01952 252892