mk1-forum.net

Hello Folks,

a friend of mine has a Mk3 Cooper S for restoration, but is missing the original engine.
He said, there are different information about the 12H397 / 12H398 Engines.

Did they came with solid wall too, or did they always had tappet chest covers?


Any hint might be useful!

Kind regards from Germany,
Niclas

All S engines had the tappet chest covers

Ronnie wrote: ↑Tue Feb 04, 2025 11:01 am All S engines had the tappet chest covers

All say this but i know one first hand Mk3 S with solid wall.

https://www.theminiforum.co.uk/forums/t ... r-s-block/

In all the years I’ve been interested I’ve never seen a Mk3 S with any real provenance that it was ever manufactured with a GT engine, and conversely a GT manufactured with an S engine. Quite a few unproven anecdotes but that’s all they are.

The Innocenti Cooper 1300 used the GT engine as Leyland could not supply the S anymore..Suppose there must have been a day when they run out of the old blocks and started fitting the GT blocks, then I suppose there was a chance that a S was going through production and needed and engine so they stuck a GT in and hoped no one 50 years later would notice!

MK3 s had a 1300 type block , they all say that when they selling one with wrong engine.
Leyland were still making new cooper s blocks in 1974 !

Every single Mark III S had the proper S block. The last few cars are reputed to have been fitted with an EN16T crankshaft however.

On the UK Market / production it appeared all cars were fitted with open Tappet Chests and had bolt on covers, though, that's not certain, however for other markets, they did use solid Tappet Chest Blocks. Our locally produced Clubman GTs had these for most of their production. While they were a Solid Chest Block, they were machined for the S Cranks and assembled with all other S Parts. While we did produce the cars and assemble engines in our local plant, these engines were imported as completely built up units from the UK. Prior to using these Blocks, they were fitted with S Blocks.

A other Question to MK3 S. Some Guys and Books say the Engine was painted black but i always saw only green Engines in original Mk3 S Cars...

I saw a reasonably paced change-over from green to black. And so far as I recall, from the Mk3, all black. Although that's not to say that a few early Mk3's had greens. Could be wrong of course but that's my opinion as a Cooper and S fan at the time with an eye for detail

My Mk3 the engine was black, and it had the mk1 type boot handle and not the newer pressed type that a lot of mk3's have, but as Peter above I believe they went from green early to black. OOooo I forgot to mention August 71

My car is December 1970 and the engine is green.

Cheers Jim

Iirc the S engines were not built at Longbridge....?

The very first Mark 3 S (RRX***H) was at Mini Machine around 1991 and the engine was bronze green. The engine in our Sept '70 1275GT certainly was.

My Mk3 S was an S block on a J reg and green engine paint, we had a 72 clubman with a green engine (owned from new), couple more clubman GT's 70 and 72 both green engines yet my 72 Innocenti Cooper has a black engine (engines were UK built). I always thought engine colour changed from green to black between 72 and 73.