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MG Midget and Sprite Technical - engine numbers

Hi all,
I have a repalcement 1275 engine for my midget project..
Just a quick question..
the engine serial number plate on the top of the block reads 12V (which I think makes it a Marina engine, it also has the upturned oil filter)
However the block has 12G cast into it, which is for an MG 1300 mk1 engine...
Which is which?
tim
T Dafforn

the V in the engine number means 'vertical' i.e. a 'north-south' or inline installation.
The G in the casting number is just a factory part reference, and AFAIK does not depend on the ultimate destination of the engine. Marina blocks are casting # 12G2398.
David Smith

The 12G for an MG 1300 engine would be in the engine number, not cast into the block.

12V engines were fitted to Midgets and Marinas, it's the number that follows which will identify which...but the upturned filter means it is definitely Marina.
Dave O'Neill 2

Tim is it ready to go for the Midget...or is it just a bare block ?

Last years winter project for me was a 1380 based on a Marina block and there are couple of bits and pieces you'll need to get sorted for the Midget.
Dean Smith ('73 RWA)

Hi Dean,
if things work out I'll be putting the engine in sometime next year.
I've got the Marina engine complete minus the backplate and flywheel..
I picked up a Midget backplate at the weekend..
From what I have read I also need a:
flywheel (machined to fit the marina crank and altered for a type 9 conversion)
frontplate
timing chain cover
Sump?

Have I missed anything?
Tim
T Dafforn

I'll check my notes but yes they were the main bits.

You can reuse the marina sump but it has an extra mounting on the bottom which is superfluous. I've got an oil temp sender on my midget sump so I did move the whole sump over.

The one area I was left with remaining confusion was the front plate/timing chain/timing cover. Mine came already fitted with front plate, duplex chain, tensioner and appropriate cover (with the bulge) so I didn't have to change anything. I seem to recall research at the time suggested the Marina normally had a single chain and tensioner. So you need to either....

-Drill the Midget front plate to accept the timing chain cover with bulge (2 extra holes i think) and keep the tensioner.
-or remove the tensioner

Other bits that tripped me up...

I had a tee piece on the midget block for oil pressure switch and oil pressure guage. There wasnt room on the Marina block for the T piece.

I stupidly didnt realise it was a different thread on the oil filter until I tried to screw on my spare Midget one literally just before I filled with oil and wanted to start. (Doh)

When i added my oil cooler back in via a sandwich plate that fouled the Distributor and I had to move the drive round a tooth or so.

My block came with a Minor back plate that fouled the Midget clutch slave cylinder (std ribcase gear box)


Dean Smith ('73 RWA)

The Marina block I have has a chain cover (the one with the vent, like yours in the picture..
From what I have read, although I have not checked this out, the marina has a single chain and a better tensioner than the midget block..
Not sure about the pro's and cons of changing to a twin chain and the old style tensioner.
Cheers
Tim
T Dafforn

My final timing/tensioner setup


Dean Smith ('73 RWA)

This thread was discussed between 21/02/2010 and 22/02/2010

MG Midget and Sprite Technical index

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