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MG Midget and Sprite Technical - Early 1275's

Were the early 1275's with the EN40B crankshaft always thin flange blocks? And would the early ones have forged rockers instead of the pressed steel ones?

I'm asking because I'm just inspecting an engine I'm about to sell, it's an early North American Market one judging by the number. I've found it has forged rockers, standard bores but with flat top pistons and the better EN40B crank. It's a thick flange block with no fuel pump hole. It looks completely standard and unmolested apart from the pistons.

It was a nice surprise to find the EN40B crank but I'd always thought they were only in the early thin flange blocks.
John Payne

Early 1275s did have forged rockers.

The EN40 crank was introduced for the thin-flange block, but there may well have been a number of EN40 cranks in stock when the stronger blocks arrived.

The cranks were, of course, also available from Special Tuning.

I've stripped quite a few early 1275 engines and they also tended to have a Cooper S style head casting, with the circular bosses with brass plugs in the middle, although with the 12G940 casting number.


Dave O'Neill 2

Cheers Dave, I’ll check the head for those bosses. I’ve put it all back together now but easy enough to take the rocker cover off. Looks like it’s had a partial rebuild at some point, crank is std but big ends have replacement shells. Mains are on original shells but very worn. Should make a good 1293 race engine for someone.
John Payne

I have an early 1275.(12cc1208) Its thin wall with the EN40 crank and forged rockers but it does not have a fuel pump hole
Apparently the stronger crank was used as the thin wall blocks flexed and there were issues with main bearings. The thick wall block was apparently introduced to stop this and the crank was made of a cheaper material. Of course the ST cranks were En40.
Bob Beaumont

This thread was discussed on 03/03/2024

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.