Some interesting facts have come to light on the Mk1 forum, it seems the 1275cc Cooper S engine did find its way into early production models of the ADO16 (BMC 1300 models) in 1967..........
ADO16 cars did have S type engines fitted from June to September 1967 and this is no myth. Think about it the 12H 1275cc engine was first built post September 1967. In order for BMC to provide a 1275 cc ADO16 from June 67 they used the 1275 cc S type engine as a stop gape. Some claim less than 900 cars were built.
These engines had an ENB40B crankshaft and con-rods with tappet chest covers and are known as 12G engines: - buyers of early BMC 1100 / 1300 cars had the option of 1098 cc or 1275 cc engines. The first 1275 cc engines were suffixed by engine number 12G and are extremely rare. These engines all had a 9 stud cylinder head, AEG510 cam, forged rocker assembly and the EN40B crank with smaller 1.5/8 inch journals, connecting rods, crankshaft diameter being the same size as the Cooper S engines. The cranks were all marked EN40B and dated. They also all used a single 1½ inch carburettor. This engine was only fitted to the very early MG, Wolseley, Riley Kestrel and Vanden Plas which were called the 1275 model. Some refer to this model as the Mk1½ in the 1100 club.
In November 1967 BMC introduced a completely different 1275 cc engine block, crankshaft, connecting rods and these were suffixed by engine number 12H. These engines were used in the normal run of the mill BMC 1300 cars and 1275 GT Mini from 1969.
To further complicate matters the very early 12H 70 BHP engine had an EN40B crank with 1.5/8 inch journals, and large valve 11 stud cylinder head. These engines are solid wall blocks and date from late September 1967 and were only used in the Riley and MG 1300. It is important to remember that the EN40B crankshaft out of this solid wall engine has a different centre main bearing width.
The 12H 70 BHP engine a sister of the above had an EN16T crank with 1.3/4 inch journals, heavier connecting rods, same pistons and large valve 11 stud cylinder head. These engines date from November 1967 and were only used in the Riley 1300, MG 1300 and Austin / Morris 1300 GT. This same engine was also fitted to the Innocenti Cooper 1300.
Years ago Dave Gilbert explained to me this piece of information was not common knowledge in Mini circles as smart individuals kept these facts undisclosed? Dave was of the opinion that all the 12G tappet chest engines ended up in Coopers and the early 12H solid block engines were used in motorsport.
There are 4 surviving Riley Kestrels with 12G tappet chest engines here in Northern Ireland. I understand the 1100 Club know of 12 surviving cars made up of MG, Vanden Plas and Riley Kestrels in GB. It is also believed over 100 survive in North America.
The 12H 70 BHP engine with EN16T crank and 11 stud cylinder head all had twin 1 ¼ HS2 carburettors and close ratio gearbox. It is worth pointing out that the 12G engines had a 3.44:1 final drive ratio later changed to 3.65:1 when the 12H unit appeared.
(Many thanks to 'Supersonic' on the Mk1 forum for the above info)
More Details Here:-
http://mk1-forum.net...php?f=5&t=12136
