Has this engine had a rebore ?

[jameswallace]

I've got a midget 1275 engine in my Mog, but don't know the history prior to my acquiring said device. I had the head off today and there didn't seem much of a step around the lip of the bores, quite a bit of carbon around number four bore's valves, and quite a bit of tan deposits on all the inlet valves ? The pistons had the following numbers stamped on their tops - M 2210 V16.

Over to you guys

Jim

[Alec]

Hello Jim,

if it doesn't have something like 010, or 020 then it is likely to be standard bore.

Alec

[bmcecosse]

The carbon on #4 bore valves suggests aproblem with the rings/piston in that bore. Easy enough to drop the sump and push that piston out for inspection. Tan deposits on valves are normal. As Alec says - oversize pistons are marked as such.

[Kevin]

Hi Jim your engine sounds similar to the one I got a little while ago and I decided to check it out fully before dropping it in as I have done this before taking the sellers word as to its condition without any paperwork to prove it and twice have had issues in a short space of time.
Well I pulled the head and found that the exhaust valves were quite recessed so the head needs sorting, but the bores sound the same as yours (mine is a silver seal engine) on looking at the block from the underside I found it was sleeved to bring it back to the original bore size maybe yours is similar, but I also found the big end & main bearing shells had just started to go through to the copper and that the cam bearins are quite poor especially the middle one with quite bad scoring although the cam appears to be OK. Sorry to have gone on a bit but mine is turning into a possible full re-build and I hope yours is less so.

[bmcecosse]

Many blocks were sleeved from the factory. And yes it's always worth checking the shells, but don't worry too much about the cam bearings.

[Kevin]

Many blocks were sleeved from the factory

Really why was that?

shells, but don't worry too much about the cam bearings.

Well I don't think scored cam bearings are a good thing and I hope that Jim's are in better condition than mine.

[jameswallace]

Thanks for all your input chaps, Plenty for me to think about. I'll see how it runs for the next few months before doing anything more - at the moment I'm looking into an overheating issue which is featured on an other thread.

Jim

[bmcecosse]

Porous blocks from the factory - many were sleeved. Scores on the cam bearings don't matter too much - and it's quite a job to renew them - certainly not practical at home.

[youngun]

Yeap, my 948 block has Liners in it!

[bmcecosse]

Ahh - now that's different - these will be aftermarket liners - it was the 1275 blocks that ran in to casting quality problems. I've seen many 1275 A+ Mini blocks with liners fitted.

[Kevin]

Scores on the cam bearings don't matter too much

We will have to disagree on that point as I am sure any engine builder would as well as bearings when all said and done are there for a purpose.

and it's quite a job to renew them - certainly not practical at home.

Agree but for my local machine shop remove the old ones press the new ones in place and then ream them is run of the mill work, and I am not going to a lot of effort and leave something that I know is badly worn its almost as bad as not changing the oil pump.

[Matt]

To a certain extent I do agree with BMC on this one, they are less important the big end bearings, however if worn they should be replaced.

One of the bearings in my current engine isn't wonderful but the cam has no play and rotates freely so I decided to leave it, afterall the 948s dont have cam bearings at all AFAIK and it just runs in the cast iron of the block

[bmcecosse]

WORN is one thing - but a few 'scores' won't matter at all - could be said to help distribute oil around the bearing surface ! But - if the block is going for full reconditioning anyway - yes indeed, change the bearings. BTW - the modern bearings don't need reaming these days - they now come sized correctly for press in fit. The point i'm making is that folk shouldn't panic if they see some scores etc on cam bearings - they really are not that important, and certainly don't take anything like the punishment big-end and mains have to sustain!

[Matt]

Thats my opinion too BMC, just written in a more understandable way!

[Kevin]

Right to clarify things for myself I resorted to the current UK information expert Keith Calver and guess what I found
I got to thinking that it’s weird how the cam bearings were always marked in some way when I stripped the engine, despite meticulous cleaning prior to assembly.
I decided to start leaving them alone, providing they were a good fit on the cam, i.e. no excessive play – cam would turn easily, but pushing/pulling the cam gear boss about revealed no ‘slop’
I have experiencing no problems with this whatsoever, to this day, unless the bearings are really badly scored, or there’s excessive play, I leave them alone
So it looks like I may be panicking over nothing so I will have to check things out a bit closer before finally deciding which way to go.

[bmcecosse]

Well yes - that is most folks view - but KC is hardly an 'expert'!! Many disagree with quite a bit of the 'advice' he puts in print. I would much prefer the advice of Simon Morson - or Adrian Dodd - way before KC!! However - in the matter of the cam bearings - leave well alone unless the engine has been seized due to zero oil pressure. The 'scoring' is often done while rather carelessly removing/installing the cam shaft - the lobes all too easily hit the centre shell.