13 replies to this topic

[Mk2Brett]

Hi!

Sorry for another one of these "whats my engine" threads, I've tried to piece the puzzle together myself but its a weird one to me.

 

So heres what I have

 

Engine number: 10YCTAH9269

Head: 12G940

 

Piston Head Markings: AE 21251 +.040

 

Bore width: ~71.40mm

 

So my research shows this is a 1098 Mini K engine, with a 1275 head. So thats what I thought I had, a 1098 with upgraded head.

 

I'm now redoing the head gasket and saw the pistons, can someone help decode this, my research might make me believe this is a 1098 thats been bored out to 1275?

 

If anyone can make sense of this that would be great!

 

Thanks

-Brett

[stuart bowes]

Im no expert I just remember seeing this link a while back 

https://www.classicm...archive/engines

 

so if I'm reading that right (others will correct me if wrong no doubt) a +40 on an 1098 makes it 1132 cc

 

I'm not sure you can even bore an 1100 to 1275, maybe with offsetting or something (no idea myself)

 

I was looking that up recently as well because I'm thinking of stroking and possibly boring my 998 to a similar spec (but with a 202 head)

 

the 940 head is a reasonably common upgrade for bigger valves and ports, some engineering may be required to get the compression ratio up, and for valve clearance (may have already been done)

 

all a bit vague I know and not necessarily accurate, wait for others to confirm

Edited by stuart bowes, Today, 09:36 AM.

[nicklouse]

Pictures would help.

 

but it sounds like a SA 1098 which is a big bore engine so has the 12G980 head and a filter on the block.

[Mk2Brett]

Thanks for the replies.

 

It doesn't have a filter on the block, it otherwise looks like a normal A series to me

 

I'll add some photos here

 

[nicklouse]

That number has been added when the engine plate was removed.

 

its a A series 1275 overbored engine.

[Spider]

The Engine Number is from a Mini K however the bore size is interesting as this is 1275 bored to +40.

The 1100 blocks fitted to the Mini K are from the small bore family and cannot be bored to fit 1275 pistons. My best guess here, without seeing the block, it that someone has re-stamped it with an 1100 number possibly to avoid legally changing the engine number on registration papers and possibly for insurance purposes.

Have a look at the engine steady end of the block above the flywheel housing - if there's 2 welsh / freeze plugs there, it's a 1275 block..

 

[Mk2Brett]

Thanks for that!
That is interesting news and make me a bit more happy than an 1098!

What gives it away as a 1275 block? I'm interested to learn more.

Very strange the engine number was replaced, and wrongly by the look of it.

[Spider]

That number has been added when the engine plate was removed.

 

its a A series 1275 overbored engine.

 

This guy is in Australia. By law, the factory had to remove the riveted plates from the imported engines and block and stamp the numbers directly on the block.

[Mk2Brett]

If

 

The Engine Number is from a Mini K however the bore size is interesting as this is 1275 bored to +40.

The 1100 blocks fitted to the Mini K are from the small bore family and cannot be bored to fit 1275 pistons. My best guess here, without seeing the block, it that someone has re-stamped it with an 1100 number possibly to avoid legally changing the engine number on registration papers and possibly for insurance purposes.

Have a look at the engine steady end of the block above the flywheel housing - if there's 2 welsh / freeze plugs there, it's a 1275 block..

 

If I'm looking at the right thing, looks like the freeze plugs are there

 

Excuse the paint flakes, in the process of trying to clean it all up.

[Steam]

The restamped numbers on these imported 3ngines can be very scratchy u like the factory Aus numbers which are very clear.
There were also a number of engines and vehicles imported privately which sometimes were "number adjusted" prior to inspection. It was different time back in the 60s nd 70s. I have seen imported 1275 engines numbered as Aus built.

[Mk2Brett]

Well thanks all for the help! That is very intriguing and also ended up with the good news that I actually do have a 1275.

 

-Brett

[stuart bowes]

note to self check where OP is from before answering lol I was assuming this to be just UK stuff

 

glad it turned out to be what you wanted

[timmy850]

It’s also an A+ block judging by the location of the alternator bracket

As Spider says, you will see ones like this occasionally where they stamp the original engine number on a 1275 block to avoid getting it certified or changing the brakes to discs

[Mk2Brett]

Yep you're right, seems like its an A+ based on the distributor type.

 

Mind blown, I had not even thought about that.