Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - 1275+060 block worn out.. Can I sleeve it?

Starting an engine rebuild and need a bit of advice.

When I got the car it was already 060" over and the head was off it. I put a set of rings and bearings in it but noticed the pistons were a bit sloppy. Engine ran fine but a small amount of smoke.

Car has now been sitting for quite a few years and I'm rebuilding the engine again. The engine after its reringing did about 10k miles. This time I want to do it properly. The piston slope is now very bad and top ring gap 026"

So what do I do. I don't think it can be bored further. There's not much metal between 2 and 3 and when I took the head off I could see that it had blown between the cylinders.

It's a 1275 block so a replacement would be awfully expensive if I could even find one.

So can I sleeve it or do I put some new pistons and rings in it and just live with it?

Greg H

You can sleve the block or go to 73/73,5 mm but the las 2 options are not sleeveable anny more.
So after that the block would be scrap.

Sleeve and go back to a sensible size
Onno Könemann

I dont think its a big deal to re-sleave... its a matter of just finding a good machinist to do the work.

I was thinking doing the 1380 overbore was only possiable if the current overbore was no bigger then .40 over,

But Onno has the inside track of doing the 73/73.5mm (1380s) overbore, so I have to defer to him.

Got a quote to sleeve it $130 a hole so $520. I think this is what I'll do.

Not many midget part suppliers in Aus. I did find one place who listed a block for $520 which sounded ok but then when I spoke to them they only had a sleeved block with pistons that was already .030" over and wanted $800 for it. Too much for a block that's already half worn out.

I'll sleeve it back to standard to give me as much life as possible.
Greg H

Hi Greg

With a 1275 sleeved block the max safe overbore is +20. The +30 'sleever' would be a no-no anyway.

P Burgess

My 1275 block was dry-linered for the USA - the factory would sleeve with better quality steel which wear more slowly so the engines would pass the then existing emissions test at high mileage.

Anthony Cutler

Hi Anthony

I never knew that. I have seen poor quality blocks and damaged blocks linered by BL and then sold as Gold Seal but didnt know BL linered blocks for USA use.

P Burgess

Hi Peter

The downside is... when I wanted to bore my block out to 1330, I was told... 'sorry, it's dry-linered; can only take it to 1293; would not risk any more.' Same as you recommend.

It explained why the engine didn't smoke at 110K miles; the bores were in fine condition; the rings however...

Anthony Cutler

So can i assume anny linered non gold seal block was an us block?
I have just pulled apart a 1275 and have reason to believe it has not been rebuild before.
So i was surprised to find liners.
Was a 12 CE block
Onno Könemann

my USA 1275 ('74) was not sleeved

I've heard the gold seal blocks were sleeved.

But never heard about "USA blocks" being sleeved, nor read it in any of the books.

Norm Kerr

Hi Onno

My understanding of the situation. BL moved block production to Qualcast (Leeds, I believe) in the very early 70s for blocks. At the BL assembly plant it was found some bores were so poor they couldn't be used for standard production engines. This is for B series BTW,the same may obtain to A series blocks. The new blocks were put to one side and then 'reconditioned' with liners to accept standard pistons. as far as I know the engines became Gold Seal units, which looked good for the quality of Gold Seal even though it was not on purpose :)

With the standard size B liners and any A series 1275 liner +20 is the max bore to leave enough
liner wall thickness for integrity.

P Burgess

Neither of my 1275 blocks are sleeved.
Trevor Jessie

I bought my 73 Midget in 1977; it had barely had a service, let along a replacement engine.

The fact that a sleeved block found its way into UK production might indicate the reverse might also be true.

I can't remember where I read this... but can assure I wasn't dreaming at the time!

Anthony Cutler

Hi Anthony

Off topic....did your car have baiased needles in the su's?

P Burgess

My liners look like they are thick enough to accept bigger (though i plan +020)
And the block had a 12CE tag and the goldseals had their own code.
Onno Könemann

My Midget was built in January 1971, and has its original engine with a 12CE block.

The quality of the block is shocking - "porous" was the way the engine rebuilder described the bores. I had anticipated that it would need to be bored out +20, but after this was done, it was apparent that it would have to be sleeved back to standard - it wasn't useable after the overbore!

Supports Peter's point about the B-blocks. Though my A-series block made its way into an engie without being sleeved at the factory...


No - the needles were fixed.

The first biased ones I saw were on the HS6 replacement.

The car was built on 9, 10 and 11 January 73... and was one of the first with an alternator; the 3 plastic-sleeved mounts were still being drilled on the bulkhead.

The car had just had a 'full service' from the garage I bought it from... even so, rusty water came out of the hub swivels when I greased them. Compared with my earlier 1098, it felt very civilised... happy days!

Anthony Cutler

This thread was discussed between 14/02/2011 and 16/02/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.