Morris Minor Owners Club

how can I tell if a Midget engine is a 1275cc with out taking the head off ( engine numbers?)
regards Phil

The oil filter layout is the same as the Minor whereas the Marina & Ital have a rear upright angle mounted oil filter also all 1275cc have the water valve for the heater at an angle and on the right hand side of the block where the minor has 1100 on the ID plate the others have 1275.

No cover plates for the tappet chests - solid block under the exhaust manifold. Head could have been changed - so not a dead reliable test.

Doesn't the engine number start with "12V" for a 1275, and "10" for a 1098?

The 1275 Midgets had the prefixes 12CC or 12CE up to October 1972 and
12V therafter.

There you go then, a definitive answer. Unless it's a recon unit and they've put their own arbitrary number on there like my 1098 from Bull Motif.

thanks mine is a "12v" engine number . from just looking at the
bores you cant tell . The stroke must be longer
Regards Phil

phil63 wrote:thanks mine is a "12v" engine number. from just looking at the bores you cant tell . The stroke must be longer
Regards Phil

Eh? Surely there's a huge gap between no.2 and no.3 in the 1098 block but only a few mm in the 1275 block. It's definitely larger bore. It's the 1098 that's a long-stroke version of the 948 block.

Someone with a manual handy will be along to tell us what the bore/stroke are for each of them...

And the 1275 is an even longer stroke

1098cc
Bore 2.478 inches or 62.94mm
Stroke 3.000 inches or 76.2mm
1275cc
Bore 2.78 inches or 70.61mm
Stroke 3.2 inches or 81.28mm

NO! The 1098 engine is 83.72 mm stroke - it IS the longest stroke A series. And the bore is 2.543" (I know, mixed units) - the figures above are for the 948 engine, not the 1098.

The BMC workshop manual agrees with those figures for 1098 bore and stroke

NO! The 1098 engine is 83.72 mm stroke - it IS the longest stroke A series. And the bore is 2.543" (I know, mixed units) -

Oh dear thats what I get for looking at the wrong page

YES! and the full dimensions are bore 2.543 inches or 64.58mm and the stroke is 3.296 inches or 83.72mm

So - by fitting a crank from a later 1098 Sprite engine into the 1275 block - and a little bit of boring and fiddling with piston crown heights - you can get a 1400 cc Minor !

Thanks for all that info, I was looking at the heads when I said that I couln't tell the differce in the bores , the diameters look the same if you compare them side by side , but measuring the bores shows the difference . All I have to do now is unsieze no 4 piston !!!!!
Regards Phil

All I have to do now is unsieze no 4 piston !!!!!

Try a bit of Diesel fuel as this can help unstick things.