Piston rings

[Tom and Maria]

Okay, currently building up my spare engine as the current one is losing a lot of oil and the big ends are knocking.

The new pistons have a brass(?) oil control ring which is concertinered and won't compress in the usual way to fit into the groove. The thin shim like rings which go above and below it (in the same groove) fit well. Should I use a large jubilee clip or similar to compress this brass ring down until it wil slide in to the bore?

Any tips very welcome!

Tom

[bmcecosse]

NO! It's a 'spring' to keep the two thin rings apart - and note the thin rings must go in right way up. Are there instructions with the ring set. ONLY use your fingers (and lots of oil) to gently ease all the rings in to place. A jub clip will never be completely round and will cause problems. If you can't mange with fingers - get a real piston ring compressor.

[Tom and Maria]

Thanks, I shan't be using a clip then.

It certainly does keep the two thin rings apart, but seems too long to compress enough to fit in the groove. I guess it must compress enough, and that is why it has the bends in it. Looks like I'll be needing a ring compressor.

Tom

[Tom and Maria]

Should I trim the brass spring ring to the correct length? It really is too long to compress properly in the groove.

I can't see it doing any harm??

[bmcecosse]

First - is the groove completely clean - no 'carbon' in it. Then try the spring in the groove without the two oil scrapers - it should fit.

[bmcecosse]

I've never had to trim them - it should fit.

[Tom and Maria]

The groove is clean as a whistle. I fitted the spring first and it protrudes from the groove a lot. It would almost join up if laid on the outside of the piston, if you follow me.

Looking online it seems that a compressor may squidge it down to size. Perhaps I'll try compressing it without the other thin rings on and see what happens. Confusing, as other sites mention trimming and the instructions mention nothing.

[bmcecosse]

It is a springy ring and should easily compress down into the groove - the little 'castelations' closing up on each other. You can try to make a spring compressor with shim steel (or thin tin-plate cut from a biscuit box base wrapped around and then a jub clip round that. I do have a compressor - and yet I always prefer to use my fingers. With a compressor - you can't SEE what's going on.

[mike.perry]

Stating the obvious, it is the correct size ring for the piston size? Are all the oil rings in the same packet? Are they in the same packet as the compression rings?

[Tom and Maria]

Yep, all in the same pack, and the oil scrapers fit fine, it's just this brass expander. There's no way it could be compressed with just fingers. All the other rings are fine, I just can't get my head around these. It's like they need to be squashed to size, but it would be the equivalent of taking about 1/4 to 1/8 of an inch out of the length.

The pistons have five rings, two oil control rings. The others are the square type with slots in and go on fine. Maybe I should just run with them?

[bmcecosse]

NOOOO ! You must have the oil scraper rings fitted...... and they must be right way up - take great care over that.

[Tom and Maria]

Tried again today and it fitted without any trouble at all. Just have been having a funny five minutes after spending all day in the workshop.

Thanks for all the replies and for stopping,e doing anything silly.

Tom