Help me ID my 1275

The 1275 I'm rebuilding was a spare engine from a guy who sold me a 72 midget parts car. It sat in his shed for 25 years.

I'm wondering what year the engine is and what car it came from.
Does the code tell us anything specific about the engine?



thanks for any help!

Fred

TulsaFred said:

The 1275 I'm rebuilding was a spare engine from a guy who sold me a 72 midget parts car. It sat in his shed for 25 years.

I'm wondering what year the engine is and what car it came from.
Does the code tell us anything specific about the engine?

thanks for any help!

Fred

Click to expand...

It's an early engine, probably '68 or '69. It's a little odd though as the "C" should immediately be followed by a C, D or J. By '72, 12V was already in play. I don't think I;ve ever seen a single letter like that. If it's a very early engine (12CC) it would have a thin flange block. - (refers to thickness of flange casting where the oil pan attaches) It'll be closer to 1/4" thick instead of closer to half inch or so.

I don't think it's a 12CC because I don't think the numbers an that high. I think the same with 12CD, so seems most likely tp be a 12CJ, which would bring it to early '70.

BTW, "Da" refers to close ratio gearbox, "H" refers to High compression engine, and the rest is the serial number.

Sprite Mk4/ MG Midget Mk3 1275cc 12CC or 12CE home market
.. .. .. 12CD or 12CJ N. America
.. .. .. after Oct '72, 12V/586F/H home market
.. .. .. .. 12V/671Z/L N. America

What about the DA after the slash?
Isn't that a 12CD type engine then?

Fred

TulsaFred said:

What about the DA after the slash?
Isn't that a 12CD type engine then?

Fred

Click to expand...

Fred,

No, re-read what I wrote above. There should always be 4 letters until you get to 12V where the sequencing code changed... i.e., 12CC DA, 12CD DA, 12CE DA, 12CJ DA The "12C" is an anomaly and so other clues like the flange are necessary.

Minis have different code sequencing, and I can't find any record of any that are "12C" alone. You sequence is definitely Sprite/Midget.

My guess is that if it's not a replica plate, it was a stamping error or perhaps some "undocumented" or in between version

This is a pretty comprehensive guide to most if not all BMC engine codes:

https://gerardsgarage.com/Garage/Tech/BMCengineCodesLO.htm

Agree with Gerard. Check the thickness of the flange on the block. If it is a thin flange (nominal 1/4" to 5/16"), I'd call it a 67ish block. A lot would depend on the original head. If it is pre-smog, then it is definitely 67. Remember at that time, BMC wasn't hung up on model years like the US manufacturers. IMHO, BMC at the time was probably starting to divert 1275 blocks from the Mini application and just began the numbering sequence with '12C'. Every now and then I come across one of these. Most thin flange blocks appear labeled 12CC which is what most of the books tell you is the first version of the 1275 exported to the USA.

Good engine internals. Should have the nice 521 rods, maybe an EN40B crankshaft too. High compression meant a whopping 8.8 to 1.

Good luck on the rebuild,
Mike

Thanks guys,

Sorry Gerard, I overlooked your discussion of the DA notation.

So when I get back to my shop I'll see what I can make of the "flange" thickness 1/4 vs. 1/2".

I believe the head has block offs screwed into the air rail holes, so the head would be a "smog" head I assume.

I know for sure this is not a replica plate. The guy I bought it from had the 72 midget sitting in a field since about 1984 and this engine in an outbuilding overgrown by shrubs and weeds. I don't think that shed had been opened since 1984 either. To him it was just a bunch of old junk to get rid of. $200 for the complete car and the spare engine, and the seller thought he was ripping me off (maybe he was!). No "classic car restoration" guy that's for sure...he he. I'm laughing thinking of that old guy buying a "replica" engine plate for it...!

It seems I have a mystery engine.

Fred

TulsaFred said:

Thanks guys,

Sorry Gerard, I overlooked your discussion of the DA notation.

So when I get back to my shop I'll see what I can make of the "flange" thickness 1/4 vs. 1/2".

I believe the head has block offs screwed into the air rail holes, so the head would be a "smog" head I assume.

It seems I have a mystery engine.

Fred

Click to expand...

Well, with the additional info you provide, that would make it consistent with a CD or CJ. Since you are fairly certain it's original, I still think it is just an error in the stamping.

Wouldn't be the first stamping mistake. Ran across two blocks this summer during rebuilds/teardowns that have stamping errors in the block numbering. The number on the front of the engine just above the water pump inlet doesn't match the number stamped on the main bearing caps. Maybe a long night at the pub? Just off by one number, but still the caps don't match the block number.

I've got a bunch of engine number plates that I've removed from the race engine blocks. My surfacers didn't like cutting through the steel twist rivets, so I would remove them. I'll look for them tonight and see if there is a "12C" in stash.

Keep us posted on the oil pan flange thickness, every mystery deserves an explanation. Also, check the block casting number that shows up under the block drain plug/oil pump suction boss, on the manifold side.

Mike

I dont think its a stamping mistake, mine is exactly the same. The only clue I have as to what mine came out of is that it has a mechanical advance distrubutor out of a mini cooper S and the head thats on it has smog fittings.

The distributor was likely switched, but that dizzy was apparently used until July '67 .Mini blocks are not exactly identical and need to be modified to work in-line. I can't imagine someone would have gone to the trouble. Usually it's done the other way around as finding a 1275 Mini is much harder than finding a 1275 Spridget.

OK
here is the flange thickness. Looks like a thick one:


and here is the casting number on the block:


Does this shed any further light?

Fred

TulsaFred said:

OK
here is the flange thickness. Looks like a thick one:

Does this shed any further light?

Fred

Click to expand...

Yes, definitely thick flange. The casting mark is typical. I have a thin flange block (12CC), but I have it in storage, so can't get a look at it to see if the number is different.

Are there any important differences between the 12 CC, 12 CD, 12 CJ, and 12 V engines?

I have the 1275 from the 72 midget itself, and it is a 12V. Being that this car was in an open field, the 12V engine has more external rust and corrosion so I'm not rebuilding it at present, in favor of the above engine (that was stored in a building).

Fred

Curious as well.
What would be the best block or the ones to avoid and heads as well and why??
Are there some that are better than others???

Kurt

In my opinion, the early (12CC) is the most desirable, not for the block, but for some of the internals. The Cooper rods and rockers for starters, and then the EN40B crank which is highly sought after. The other is the non-SMOG head. There doesn't seem to be much in the way of documented changes in the block beyond the thicker flange casting and revised main caps and dowels with the 12CD.

From a racer's perspective, the most desirable block is the 12CD with a thick flange, the solid center main bearing web and no factory thin wall sleeves. All the block stiffness ever available in a production Spridget block. These blocks are rarer than "hens-teeth". There is no hole under the center main bearing and with the thick oil pan flange, the block is as stiff as it gets. Resists high rpm flex and hence bore distortion and crank flex. I've seen only a few of these in my 35+ years of Spridget addiction. The thin wall sleeves make the block unusable for SCCA racing (limited to +.047" overbore). These blocks can be used for 1380's since the bore/hone cuts the sleeve completely out.

Connecting rods are good in all years with the AEG521's being slightly better material wise (EN24 vs EN21) than the AEG625's. The EN40B crank is nice, but the EN16T's are good too. Most really serious SCCA FP race types transition to the Moldex or Farndon crankshafts anyway if they are really serious about racing for a National championship. And, they probably use Carillo connecting rods with these cranks as well. The early 12G1316 smog heads (up until about 1970/71) have the good exhaust port shape as well, so its a toss up to me whether its a pre-smog head or not. There are other characteristics to the head casting that are more important when considering a cylinder head casting for a full porting race head.

FWIW, When I said pulling a "Mini block off the line", I was talking about the rough casting for further processing into a Spridget block (different main caps & the threaded oil pickup hole, maybe some other little things too). If you have a 12V block, sometimes there is an extra boss cast on the front side of the block just under where the alternator would sit. It looks to be a boss for a drilled tapping that is used with the Mini front engine mounting plate. Some of the front plate gaskets have a piece of material that goes out there for it. When the SCCA FP guys were looking for a block to use for a full race dry sump engine, they could adapt a Mini/Austin America block with a good bit of work. The A+ blocks were nice too. extra webbing and stiffness. Had to do a good bit of machining to get things to work, but at that level of racing, cost was not that significant a concern.

HTH,
Mike Miller

PS: Nice pictures. I'm still confused on the simple straight forward way to insert them into the topic threads. Any help would be greatly appreciated.

Excellent thread, guys, and Gerard, thanks for the great engine info on your website.

My MK III Midget's engine plate is gone. I do know that is has the 1/2" flange.

Question: where are the engine casting numbers located, on the carb side or the dizzy side of the engine?

Thanks!

Carb side of the block. Close to the rear, under that boss thing that passes the oil from the pickup to the oil pump. Just above the curved section of the oil pan rail. The block drain plug is about the 1 or 2 O'clock position from the casting number if viewed from the side of the engine.

Mike

Thanks, Mike. I'll take a peek the next time I get her up in the air to change the oil. :thumbsup:

Great info guys, Thanks.

Kurt.