Engine codes?

[Bleh5150]

Hi all, I'm trying to confirm that my moggie has an mg 1275 in it. The only engine code I can seem to find is up my the thermostat housing as the metal strip by the spark plugs is missing. So my question is does anyone have a clue if I can trace the engine by this number? Many thanks

[philthehill]

On the face of it you have fitted to your Minor a 1275cc Midget or Sprite engine block.
Additional photos would be of benefit especially the distributer side of the engine.

Basically there is no way of determining the original engine number of the 1275cc Midget engine or Sprite fitted to your Minor from the information provided.

The number by the thermostat housing is just a casting batch number and bears no relation to the proper engine number.

The start/prefix of the 1275cc Midget engine will be either 12CC or 12V.
The rest of the engine number is made up as to whether the engine is high compression or low compression and the actual engine serial number.
The only way to determine if it is high or low compression is to remove the head and examine the depth of the dish in the top of the piston.
There are differences in the block as the 1275cc Midget engine was produced with a thin sump flange and a thick sump flange.

It appears that the cylinder head fitted to your engine has been changed at some time as the 1275cc Midget cylinder head does not normally have the sculpturing around the thermostat as per your photo.

I suspect that you have a Mix & Match 1275cc Midget or Sprite engine fitted.
Phil

[Bleh5150]

Ah ok, well I have a few more photos. I was guessing it would most likely be a midget engine but wanted to find the engine number so I could update the v5. Here's some more photos:

[philthehill]

Thank you for posting the additional photos.
It can be confirmed that you have a 1275cc engine block (either Midget or Sprite) fitted and it appears to be a thick sump flange block. The thick sump flange block is most sought after in 1275cc Midget/Sprite racing circles as it introduces more strength into the block so reducing the tendency for the block to warp.
Your photo of the missing engine number plate also confirms that the head is not original 1275cc Midget or Sprite as it has two threaded holes in the front side of the head above where the engine number plate should be.
Phil

[Bleh5150]

Ok great thanks for your help and knowledge, so would I be best fitting a 1275 head or is it not going to make much difference with a Frankenstein 1275 in the bay?

[philthehill]

I suspect that the cylinder head fitted to your 1275cc Midget/Sprite engine block is a Mini 1275cc MPI head which is slightly better than the 1275cc Midget head.
The two threaded hole in the head support the alternator mounting bracket.
Therefore there is no need to do anything - just enjoy.
Phil

[Bleh5150]

The news I was hoping to hear many thanks Phil for your insight. As for updating the v5 would I still be able io without an engine serial number?

[philthehill]

What does the V5 say at the moment?
If it says 1275cc engine capacity I would be tempted to leave it at that but someone on here may be able to give the legal answer/requirement.
Below is a specimen 1275cc MG Midget thick sump flange engine number:-

12V/778F/H###

As important as the V5 - is your insurance company aware that the engine fitted has a capacity of 1275cc.

Phil

[Bleh5150]

Currently the v5 states it's a 1098cc and as for insurance I haven't contacted them to let them know yet only discovered the 1275 plate recently.

[IslipMinor]

Looking at the pictures, the crankcase ventilation system hose is missing. It should be connected between the canister on the timing cover and the port of the rear of the carburettor. Also make sure that the oil filler cap is of the 'non-vented' type. N.B. This is wrong, the filler cap should be 'vented' for the 1275 breathing system.

Regarding insurance, what else has been done to the car apart from a 1275 engine? Brakes, suspension etc.?

When I contact our insurers, Norton Heritage, about fitting the 1380 engine, 5-spd gear box, disk brakes etc., 18 years ago, they were more concerned about what other changes had been made, so that the car could cope with the additional performance. After giving them all the details, the quote was much the same as before the restoration, apart from the value change.

[TFM150K]

You do need to notify DVLA of the change in engine size and if you do not have an engine number they are unlikely to be concerned - but what you do need to do urgently (assuming the car is on the road) is to establish if there have been any other mods (brakes, diff ratio, suspension etc) and tell your insurers about all of them - back-up any phone calls with an e-mail or a letter - otherwise your insurers are likely to refuse any claim.... which could leave you in the poo!
Assuming you are with a good insurer there is unlikely to be any problem and any increase in premium is not likely to be much - as long as the stopping power has been considered to balance out the engine power increase.

[Mark Wilson]

I suspect that the cylinder head fitted to your 1275cc Midget/Sprite engine block is a Mini 1275cc MPI head which is slightly better than the 1275cc Midget head.
The two threaded hole in the head support the alternator mounting bracket.
Therefore there is no need to do anything - just enjoy.
Phil

Spot on Phil. The head casting number is the same as my Mini MPI head, which I have also fitted to a Midget 1275 block. Not tested yet, but a couple of points regarding fitting of these. At the front of the head is an oilway plug, or should be, but the heads are currently supplied without and the correct plug is no longer available. I tapped and plugged mine with a set screw. Obviously has been done on Bleh's engine, as it would be covered in oil if not! The other point, though, is that the thermostat recess on these heads is not countersunk to locate a stat, as the head was meant to be used with a sandwich plate. Not an easy bit of machining at home, so might be worth checking that a stat has actually been fitted here. (I used a sandwich plate, which I have tapped for a temperature sensor as the MPI head doesn't have the normal threaded hole)

The engine number is likely to be a CE prefix, CC being the thin flange and CD export units only. While on the subject, I've asked this before with no response, but my engine has the number 14172 stamped in several places including the crankshaft flange, the flywheel and the backplate - could this be the number part of the engine ID, which is also missing on mine? (Did wonder if it could have been a date, but my engine is an early thick flange, so probably about 1968)

Mark

[philthehill]

I make no claims as to its accuracy

http://www.mg-cars.org.uk/imgytr/pdf/enginehist.pdf

Mark
The 12V engine number in my post above was taken from a 1275cc Midget thick flange block.
According to the data in the link above 12V engines were produced only after October 1972.

Were thick flanged blocks produced before October 1972?

Phil

[Mark Wilson]

Apologies to Bleh, as I might be about to go into too much detail! Neil Cairns is fascinating, but is a bit vague in places - his table only shows 12CC and 12V numbers, but he does mention 12CE elsewhere. I've only read extracts, but Terry Horler's Midget and Sprite Buyer's guide seems to be well respected:

https://books.google.co.uk/books?id=pzc ... es&f=false

He shows 12CC as being superseded by the thick flange 12CE somewhere between 1966 and 1969, and 12CE as being superseded by 12V (also thick flanged) in Jan 72. 12CD was the North American market version of the 12CE.

12CC is the thin flange version, according to Daniel Stapleton in this extract. He is quite interesting about which engine is better for tuning.

https://books.google.co.uk/books?id=V3S ... es&f=false

And as to when the cranks changed from EN40B - no, that's a different subject......

Mark

[philthehill]

Mark
Whilst I have no idea of the accuracy of Neil Cairnes MG engine details Page 36 he does states the following engine prefixes:-

12CC
12CE
12CD
12CJ
12V/586F/H
12V/6712/L

After reading the information in the second link I will dig out my spare 1275cc Midget thin flange block and see what I find.
Update:-
My spare block is similar to yours in that it does not have the engine number attached.
Looking at the centre web there is no casting hole and it is a thin flange block; so according to the detail in the 2nd it link must be a CC block/engine prefix.
Phil

[Mark Wilson]

Phil,

Ah - I'd skipped past page 36 and looked at the table on page 38, where he only lists 12CC and 12V.

I know I said it's a different subject - but do you know if your spare 12CC block originally had an EN40B crank?

Mine has, and although I've seen views that a CE block wouldn't have been fitted with one originally, I've also come across people who think that some were used early in CE block production. Makes not an ounce of difference, as it's been ground too much for racing use, but it's a possible clue to the age of the engine.

Mark

[philthehill]

Mark
I have no idea if my spare block originally had an EN40B crankshaft as it came to me over-bored to 1400cc and a EN16T tuftrided crankshaft that was re-ground to 0.010" undersize.
My understanding is that only the very early 1275cc Midget/Sprite blocks were fitted with the EN40B Nitrided crankshaft which was quickly discontinued. All later engines were fitted with the EN16T tuftrided crankshaft. From what engine number is anyone's guess and I have never come across any information to say at what engine number the change over occurred.
I suspect the change happened when BMC ran out of EN40B crankshafts.
With the EN16T crankshaft production costs were cheaper and BMC over the years reduced the material spec of most engine components I suspect to cut costs.
The early 1275cc Midget/Sprite engines were reputedly built to Cooper 'S' standards - that is the crankshaft (EN40B) and con-rod material (EN24V) was the same. The Midget con-rods were later down graded to EN21 as were the Cooper 'S'.
The tuftrided crankshafts should only be re-ground in increments of minus 0.010" at a time and then the tuftriding process should be repeated.
The three 1275cc Midget crankshaft I have are all of the EN16T tuftrided material and ground undersize by 0.010". They all have had work done to them though to increase their longevity.
You can still get 1275cc Midget/Sprite crankshafts made in EN40B but the last quote over 20 years ago was in excess of £1000.
Phil

[IslipMinor]

the last quote over 20 years ago was in excess of £1000

Phil,

They've gone up a bit now - Moss have a new EN40B Midget crankshaft for £1,830 + VAT = £2,196!

What have you done to increase longevity? Fully balanced presumably, but what else?

[Mark Wilson]

Blimey! I'm open to offers Mine is -030, I've only had it checked and polished, so don't know if the last regrind was re Tuftrided. I wouldn't really want to tear it all down again at this stage, but if it doesn't run when the car is back together.......

There's a guy on the Midget forums in the states who has exactly the same spec that I have, ie thick flange block, EN40B crankshaft and Cooper conrods and says he can trace the originality of the engine. If the matching stamped numbers on my crankshaft, flywheel and back plate originate from the factory rather than a reconditioner or balancer, I think mine is as it left the factory, despite it not being an early 12CC. Perhaps BMC found a box of bits lurking in corner....

Mark

[philthehill]

Richard
Blame it on Brexit
The cranks have been cross drilled with restrictors, wedged and balanced in both static and dynamic modes.
After the work was carried out the cranks were tuftrided and checked for trueness.
The flywheel, clutch cover and crankshaft pulley/damper (2 part lightweight racing Cooper S) were part of the crankshaft static and dynamic balance.
A 4 bolt centre main cap helps to hold it all together.
The above work was done by Oselli.
The Cooper 'S' rods have been polished and balanced as well which helps too. That work was done by Manx Racing.

Note:- There are two specifications of materials used in the production of the Cooper S rods EN24V was the original spec and later EN21 was used for both Cooper S and the 1275cc Midget/Sprite engine.

Mark
The numbers may well be the engine number; and to keep all the parts together the numbers were stamped on the various items.
Stamping the numbers on engine parts is quite common especially when there is the possibility that parts could become separated when the engine is overhauled.

What size bores/pistons do you have?
It is highly likely that your engine number tag got separated from the engine if and when the block was re-bored.
If the engine has been re-bored it is not ex factory condition unless silver or gold seal reconditioned and then the engine would have a reconditioned engine number attached in place of the original.
Phil