piston rings

[les]

I've just received a set of nos Hepolite pistons, unexpectedly they came with rings installed. Now as it's usual to gap rings, it means removing them, I'm thinking of breakage removing 16 rings and replacing. It crossed my mind that, as they are standard bore size and pre installed, they may already be gapped. Is this usual if they're already on the piston. Pleased to hear your thoughts.

[philthehill]

Les
You should remove at least one or more ring and placing it or them in the bore and check the ring gap.
If not gaped right they should all be removed and checked.
If you do not have the right gap there is a good possibility of broken rings or engine seizure when the rings expand.
I received a set of expensive pistons with rings already fitted and supposedly all ready to fit. Decided to check the ring gaps so took a ring off placed it in the bore checked the gap and the gap was too small. Luckily I have a specialised piston ring removal tool and a piston ring gapping wheel so was able to get the gaps just right.
The fitted gap for a 10MA 1098cc piston ring is 0.007" - 0.012".
The fitted gap for a APJM or 9M 948cc piston ring is 0.006" - 0.011".

[les]

That's good enough for me--off they come! What's this special removal tool?

[philthehill]

The specialised piston ring remover can be obtained from Frost.co.uk item No:820 for the Pro Piston Ring Tool @£13.28 or item No: M720 @ £8.17. With both add the usual P & P & VAT.
I obtained both the piston ring tool and the piston ring gap setting tool from Eastwood many years ago. Neither seem to be currently listed on the Eastwood web site. The Eastwood Pro Piston Ring Tool is similar to the Pro tool from Frost's.
The piston ring gapping wheel which I have is similar to the Summit gapping wheel PT No: 906795. See link for photo of gapping wheel:-
http://www.muller.net/sonny/crt/rings/index.html.

[les]

Thanks Phil, could be money well spent, I'm reluctant to chance breaking a ring. The link is not working for me, although I'm happy to gap manually so to speak, it's the removal that worries me.

[philthehill]

Les
Yes I was having difficulty with the link as well but that is what it says in the box at the top of the page.
Try this link.
http://www.summitracing.com/int/parts/sum-906795.
The above link works
or
http://www.uni-max.co.uk/piston-ring-grinder/d/

Two for sale on UK 'e' bay (Staffordshire) item No: 251591206065.
(Gwent) item No: 261369170723.
Unless you have the special tool for ring gapping there is a good chance of breaking a ring or not getting the gap square.

Before the gapping wheel I used to use a ring gapping plate which had a series of varying size concave groves machined into it in which you would place the ring and then gap using the slot cut at 90 degrees to the ring slots.
Unable to find what I am looking for at the moment if I find it that type of ring gapping plate I will let you know.

[bmcecosse]

I have always wound them off and on with a bit of shim steel - or even a feeler blade - but the 'tool' isn't too expensive. I have never had to gap rings - they were all spot on...or slightly wide. Handle them carefully - and keep them right way up! Do you have a compressor for fitting the pistons in the bore?

[les]

Thanks Phil. Yes Roy I have ring clamp for the job. I'm in the process of rounding up the bits at the moment, waiting for the conrod shells, thrusts and cam bearings. Made a silly mistake with the rods; I thought i'd trim off the casting 'flash' on one while I was tinkering, it went well. Then I realized I'd altered the weight, so had to smooth the lot. Now I will have to weigh and balance them. Wish I'd left them as now I've got to get/make a balance and some accurate scales. A classic case of one thing leading to another.

[philthehill]

les
If you have only taken the flashing off any imbalance will not be so bad. They were never race balanced to start with.
As you will be balancing against each other and not each one it will not be so bad to check for differences in weights.
For example:-
Support the small end with a small dia round bar through the gudgen pin hole and with rod horizontal attach a small digital read out spring balance to weigh the big end.
Make a note of the weight and do the other three again making a note of the weights.
Change the round bar to the big end and weigh the small ends again making notes of the weights.
From the notes you can see what needs to come off either the small end or big end - if any at all. Do not forget that what you take off you cannot put back again so you need to go slowly.
Try the weights again but with the conrod other side up to make certain all is well.
The scales do not have to be super accurate as you are measuring each rod against another not the weight of the rod but they must be able to be read in grams. A low weight digital fishing scales may fit the bill.
For balancing qty 4 conrods end for end Oselli charges start at £80.
Are you going to have the rest of the engine balanced because if you are proportionally the cost comes down as Oselli charges for that service start at £240 all in. Maybe best to leave it to be done in one hit by Oselli or a similar engine tuning/reconditioning company.

[les]

Phil, thanks for advise, I did start to make a rod suspending device, copied from the internet, your setup sounds more straight forward. I'm trying not to get too full on with this project, tempting though it is. So the rest is under consideration, the unit will end up in my van. Although I appreciate balancing also equals smooth running. My shells etc arrived today from Marle, pricy but good quality.

[philthehill]

Les
Unless you are going to do high revs there is no need to get it all dynamically balanced. So long as all four rods are balanced end to end and have the same weights at the small end and big end there is no need to go further. My first set of self balanced rods were done on a calibrated sweet shop scales which was graduated in grams again by just suspending either the big end or small end off the scales and seeing what the other end weighed as indicated by the scales; and that worked for me.
Theses days because I need the engine components dynamically as well as end for end balanced the components go to the likes of Oselli to be fully balanced.
Not cheap I know but well worth the cost.
Best of luck with the re-build.
Phil

[les]

Phil, I'll balance/weigh the rods as you say, the rest probably just concentrate on getting everything thoroughly clean, have previously drilled for oil gallery plugs so as to brush them through. Not rushing it, nice to be able to take it leisurely! Thought I ought to start though, I bought it a good few years ago!
Oselli, they've must have been going a few years now, I went to their premises years ago. I think it was for an lcb for my S. Oh dear I'm going back!

[bmcecosse]

Is this for a 1098 or a 1275 - I can't remember now.. I have lightened and balanced rods in the past - I suspended the end with thread from a lab stand and weighed the other on a set of gram scales. I had also lightened the pistons by removing most of the skirts - and then trial assembly to check height to deck - which actually worked out fine after I swapped a couple of the pistons around. The pistons were then balanced too.. This all for a very high revving 998 engine.

[les]

For a 1275 Roy, basically I'm going to make sure all small ends weight the same. I did see on u tube where a guy balanced the small end, until they were the same at that end, as per normal, then weighed each complete rod, picked out the lightest and removed metal from the caps of the others until all rods weighed the same. This as opposed to weighing the big end in a similar way to the small end. I suppose it amounts to the same thing.

[philthehill]

Les
Oselli were established in 1962 in Oxford then moved to Witney and are now at Great Horwood near Buckingham Post Code: MK170NY.
Whilst they were at Oxford and Witney it was not too bad a journey to deliver and collect parts for say re-boring or machining but them now being at Great Horwood has doubled my journey each way. The problem I have is I like face to face contact when explaining what modification(s) I would like them to carry out. That way there is no confusion about what is required (hopefully)
Oselli have done all the machining work on my 1380cc engine (except the 7 port head which was done by Manx Racing); and my previously installed 1400cc engine. Both stage 3 head and offset re-bore etc. etc.. They have done all the work on the MG Midget cranks for both engines including both static and dynamic balancing for all engine components.
As regards my experience of Oselli I cannot speak highly enough of the work that they have carried out for me over many years.
Regards
Phil

[les]

Nice when you find a company or person you can rely on. You can leave something with them and know you'll get what you want. I find these occasions are getting harder to find. It must have been Oxford where I went with my dad. It would be a rare thing if they were still on the original site!

[philthehill]

Les
A little memory lane trip for you:
http://www.mg-cars.org.uk/news/news289.html

[les]

Lovely stuff.

[bmcecosse]

How are you planning on fitting the rods to the pistons les ? I would do that BEFORE fitting the rings......

[les]

I'm going to make a jig to stop the pin in the right place, then heat the rod end to a blue colour and press the pin in rather quickly! Well that's the plan, and yes wiser without rings.