BMC 1.8 Dismantle

[Tony Brooks]

Are you sure its standard?

 

My comments about the marks being grade marks and thus PROBABLY standard need confirming by measurements. And not measurement only at the top of the bore. Just under the lip, about half way down and again towards the bottom with two measurements in each place. One across the engine and one at 90 degrees to it. Then you can calculate how much ovality is in the bore, the maximum wear and if its barrel shaped or not.

Edited November 11, 2015 by Tony Brooks

[ditchcrawler]

Found them http://www.ebay.co.uk/itm/BMC-1-8-DIESEL-PISTON-RING-SET-0-040-GENUINE-NEW-NOS-BHM-1044-40-BHM-1125-40-/351557272619?hash=item51da72442b:g:JM8AAOxy63FS0Wzd

[Cheshire cat]

Except they are + 40 and the OP is looking for standard size

[jimfin]

Except they are + 40 and the OP is looking for standard size

Can I ask what OP stands for!!!.

 

Moving on, with the small ware in the bore (to be confirmed) think I would be better to get +20's and gap them to suit.

Hope to have proper measurements of the bore tomorrow.

[RLWP]

OP - Original Poster - That's you

 

I wouldn't mess about gapping the rings. If the bores are worn enough for you to have to regap bigger rings, you need a rebore

 

Richard

[jimfin]

^{OK. I will measure again. But from memory, the new bore is 80.26 and when I measured the bore half way down it measured 80.4 ish.}

 

^{How big can it get before needing a rebore???}

 

^{Like I said I will measure again.}

[RLWP]

80.26 is 3.160", which is the standard bore according to the manual

 

80.40 is 3.165" so you have five thou of bore wear. The first standard oversize piston is +0.020". Unfortunately, the manual doesn't have any tolerance on acceptable bore diameters, so this is one for you to decide

 

Tell me again about the piston ring gaps. The gap on the top ring in the standard bore should be 0,3 to 0,43mm. What are you getting?

 

Richard

[Tony Brooks]

Just a thought. I think that you can still get Hepolite type oil control piston ring sets with the multi-piece oil control ring. With only 5 thou wear they should sort out any oil burning problem (if there ever was one) without resorting to a re-bore. If the poor cold starting has been attributed to loss of compression then this option may well not cure the problem.

 

This should also ensure you get a ridge dodger top ring.

 

Try https://www.hastingspistonrings.com/piston-rings/oil-control-rings

[ditchcrawler]

Except they are + 40 and the OP is looking for standard size

These any good http://www.ebay.co.uk/itm/MGB-AUSTIN-MORRIS-1800-NEW-SET-4-CORDS-PISTON-RINGS-STANDARD-/361384613003?hash=item542433948b:g:pFAAAOSwuTxV8GRl

[Burgiesburnin]

The amount of time and effort that you lot put into helping a bloke out is amazing!

I almost wish that I had an engine problem as well.

[jimfin]

The amount of time and effort that you lot put into helping a bloke out is amazing!

I almost wish that I had an engine problem as well.

Believe me I really appreciate it.

 

Richard.

The gap in the top ring is about 3mm. Yes. 3mm!!! I'm thinking that there would be a lot of blow by with this sort of a gap.

 

Tony.

I asked calcutt boats if they could supply standard ring and this was the reply.

 

"This is a more complicated question than it sounds!"

 

"We do have piston rings but they only fit Turkish pistons so we say no we do not supply them as 9 times out of 10 they don't fit, the best way and actually works out nearly the same price is to purchase a set of new standard pistons."

 

I measured the bore again as best I could. Like I said before, it's about 80.4 across the engine and is about 80.45 along the length of it.

 

Thought I had found some rings today bit I think they were for a 1.5.

[ditchcrawler]

Believe me I really appreciate it.

 

Richard.

The gap in the top ring is about 3mm. Yes. 3mm!!! I'm thinking that there would be a lot of blow by with this sort of a gap.

 

Tony.

I asked calcutt boats if they could supply standard ring and this was the reply.

 

"This is a more complicated question than it sounds!"

 

"We do have piston rings but they only fit Turkish pistons so we say no we do not supply them as 9 times out of 10 they don't fit, the best way and actually works out nearly the same price is to purchase a set of new standard pistons."

 

I measured the bore again as best I could. Like I said before, it's about 80.4 across the engine and is about 80.45 along the length of it.

 

Thought I had found some rings today bit I think they were for a 1.5.

Was my last ebay link any good?

[Cheshire cat]

Hmmm. More like at least double the price for new pistons.

 

http://www.mgocspares.co.uk/acatalog/MGOC_SPARES_UPPER__MGB__4.html

 

Maybe these ones are Indian rather than Turkish.

 

I notice there are three and four ring sets. I have no idea if diesel and petrol will be interchangeable.

[Flyboy]

If the engine is an original British BMC and not reconditioned, the pistons will probably be marked MOWOG which was the trademark. The block will probably have the same marking.

Edited November 13, 2015 by Flyboy

[jimfin]

More up dates. Thanks for all the links. I have checked and was told that the petrol rings are different.

 

An engineer told me that the +40's on ebay would be too big to cut down to my size bore.

 

I am in touch with a company in the UK who say they can make me up a set for about £100. If this works out, I'll let you all know.

 

This is a pic of the ring in the bore. The gap should be between .3mm and .4mm. As you can see the gap is a bit more then it should be!!!

[bizzard]

More up dates. Thanks for all the links. I have checked and was told that the petrol rings are different.

 

An engineer told me that the +40's on ebay would be too big to cut down to my size bore.

 

I am in touch with a company in the UK who say they can make me up a set for about £100. If this works out, I'll let you all know.

 

This is a pic of the ring in the bore. The gap should be between .3mm and .4mm. As you can see the gap is a bit more then it should be!!!

Try Gosnays engineering of Romford, Essex, 01708 740668. They have enormous stocks of engine parts, old and modern. Google their website. I dealt with them for a great many years.

If the engine is an original British BMC and not reconditioned, the pistons will probably be marked MOWOG which was the trademark. The block will probably have the same marking.

Racism. MOWOG went out with the Gollywogs.

[RLWP]

MOWOG went out with the Gollywogs.

 

I've never seen a piston marked MOWOG, only cast items like gearboxes or blocks

 

MOWOG Morris or Wolseley or mG

 

Richard

[Flyboy]

 

I've never seen a piston marked MOWOG, only cast items like gearboxes or blocks

 

MOWOG Morris or Wolseley or mG

 

Richard

I have seen MOWOG on A series pistons, but it appeared on many other components and not just cast stuff eg. tappet covers, fanbelts.

 

 

Edited November 14, 2015 by Flyboy

[RLWP]

Thanks for that

 

It's a bit like Fomoco - FOrd MOtor COmpany

 

Richard

[p6rob]

We we're talking about MOWOG the other day, Made On Works Own Grounds was a popular choice here. One of the guys that rebuilds gearboxes was showing me how much smoother the MG Magnette gearbox rotated compared to a modern Peugeot.

 

You can get engine sets or a single bore set of rings from F.W Thorntons. Not sure if the do individual rings but worth asking.

 

http://www.fwthornton.co.uk/

 

Extremely helpful as were the forum experts when I rebuilt my BMC 1.5 and broke a ring during the process.

 

Rob

[peterboat]

when we were looking for parts for keiths 1800 bmc diesel the local engine reconditioner managed to get the bits by the time we had done it would have been easier and cheaper to throw it and install something much newer. keith has since sold the boat as he was always dreading something else going wrong

[jimfin]

Update. An engineering chap in Ireland told me about John Cox of Cox & Turner Engineering in UK. I called him up and told him what I was after, about 10thou oversize rings for my 1.8 diesel BMC.

No problem he said. I can make them up for you, call me back tomorrow and I can confirm.

So, I did and they are now on the way to me.

Should get them later this week and I'll let you know if it all works out and contact details for John.

[Tony Brooks]

Unless you are re-boring the block I would advise that you either remove the ridge at the top of the bore or ask for a ridge dodger top ring. If you do not you just might snap the new top rings.

[p6rob]

For anyone interested, there is an article in the December 2015 issue (out now) of practical classics showing a stripped down bmc 1.8 diesel.

[jimfin]

Another update. My new rings arrived today and they are just perfect. They are a nice tight fit in the bore and I will gap them after I hone the bores.

I bought them from John Cox Ph 01425 652627

Brought the head to a local engineer and was told I might be looking for a new head. I said I might have to find a new pocket with money in it first. He is going to get it pressure tested first, if that works out ok he will be able to repair the damage. Said that it was water damaged some time ago before I got it.

You can see damage in the pics.