Piston Rings

[popleycrew]

Hi, I have just got a new set of piston rings which are 0.20 1098cc oversized set . I'm unsure about the order they go on the piston, i know the oil control ring goes at the bottom, I have a tapered ring with TOP written on it and two compresson rings.
Does the tapered ring go on the top of the piston?
Many thanks

[billlobban]

Yes

[katy]

I believe the tapered ring goes below the compression rings. The tapered ring is AKA a scraper ring, it scrapes the oil back down the cylinder. If you put it in the top groove the compression and combustion will squeeze past it.

[bmcecosse]

Sorry - I disagree with that. Where did the rings come from - and - I assume your bores/pistons are +20 thou ??

[billlobban]

Thats not my understanding I think the tapered compression ring should be above the other 2 compression rings its designed to stop the top ring smashing into any wear ridge at the top of the bore.

Roy?

[bmcecosse]

Actually -I would expect all 3 rings to be slightly 'tapered'. If you squeeze them gently in your hand - they should bow slightly indicating the taper. The top ring is sometimes 'stepped' to avoid a wear ridge - to be honest - I think it is best to rub away any obvious wear ridge with wet/dry paper and not rely on a step. And if the wear ridge won't easily rub away - you need a rebore.

[les]

If they are taper rings and new you should see the word Top etched on one side of the ring.

[katy]

Was there no instructions with the new rings?

If the cylinders have not been rebored and new rings are being installed, any ridge at the top of the cylinder should be removed with a "ridge reamer". Also the cylinder should be de-glazed.

On page AA.14 of the BMC manual, it states:

On later models a tapered compression ring is fitted in the second groove from the top of the piston, and, commencing at engine No. 121585, a tapered ring is also fitted in the third groove to improve the oil control (see Section AA.38). It is important that the narrow side is fitted to the top, and to identify this top face is marked with the letter ‘T’

Unless the ring manufacturer instructed it, I sure as heck wouldn't want to put a tapered ring in the top groove, that ring has the hardest job of all to do, in the worst place of all.

[bmcecosse]

Oh well - the Manual will be right! As I said earlier - I would expect all the rings to be tapered from what I remember a few years back.

[billlobban]

Interesting site http://www.grantpistonrings.com/aboutus ... rofile.htm - never knew there was so many different types

[popleycrew]

Thanks for your replies and for your help!

The cylinder bores were bored out to take the oversized pistons/rings and has been deglazed. The instructions were not all that clear as the piston set was for many different variants. I got this set from Bull Motif which is normally ok with bits and pieces. My understanding of the pistons/rings is that to have a 'tapered scraper' to stop unwanted oil escaping to the top of the piston which would make sence to have it in the middle. It is very confusing as I didn't relise how many different types!
I guess I need to try one way or the other!

[billlobban]

Just to add some more interest to the confusion http://www.omegapistons.com/index.php?o ... &Itemid=47

If you bought them from Bull Motif give them a call and tell them you have a question about the piston rings they will give you the phone number of their supplier (I had it until recently) who are extremely helpful about all things piston related. They will give you the definative answer.

[popleycrew]

Yes, I will phone them up I was thinking about doing that.
I will need to place another order with them soon.. a new clutch kit!

thanks

[Mogwai]

In most cases on any engine the top ring will usually be chromed & of a different material spec to the lower rings due to the harder life it has .
Also how were they packaged ? as in my experience rings sets are usually in marked wrappers or packed in order

[popleycrew]

The piston rings go in the following order.. oil control, 1 compression ring, tapered ring making sure 'TOP' is facing upwards and compression ring, I made double sure and phoned them up.

If you are interested in my progress here is a link to my youtube channel http://www.youtube.com/user/popleycrew

[bmcecosse]

You say it's a 1098 engine - and it does look like a 1098 'thick flange' block - yet you have a 948 backplate on it ?? Your 'quarter' mark is of course 1 and 4 mark - indication of 1 and 4 pistons at TDC. The lock tabs are best folded over with vice grips - rather than chisel etc. I couldn't quite hear your conversion of ft.lbf units into newton metres. But 1 Nm = ~.75 ft.lbf. So - 40 ft.lbf ~= 53 Nm - not '80' as I think you say on the video clip?

[katy]

Thanks for the comeback w/that info. Now we all know.

[billlobban]

We bow in the presence of your superior knowledge

[bmcecosse]

The torque conversion is quite worrying if others were to follow the video.......... Could lead to some stripped threads - IF I heard the video correctly - it seemed very quiet.

[popleycrew]

thanks for your comments. As you can tell i'm not a trained mechanic im just doing this as a hobbie and yes i probably will make mistakes. As for the conversion into newton metres im following the conversion table which came with the torque wrench. This engine im working on may have a different backplate which im not aware of and it has been 'messed about with' before I brought this car/engine.