[David Herbert]

Paul,
The tanks in the UK with plugs welded into the exhaust holes in the rear plates are vehicles after Shop number 247 that were BUILT with the later exhaust arangement but were using up stocks of the earlier plates, which had been fully machined and at that point in the war could not be wasted. There must have been quite a few of these as I have seen at least six on ranges in the UK including tanks without side doors. It was much more common on (I think) the LH plate than the RH (could have been the other way round) so there were tanks with one side with a welded hole but the other plain. Relatively late in the war the early Rams being used for training in Canada were remanufactured with various late fittings. I have not seen how the exhaust openings in the rear plate were plugged but the 'production' ones were pieces of plate the same thickness as the main plate, welded in flush from both sides. When painted they probably would not show in photos at all.

In terms of the exhaust and inlet fittings on the actual engines, R975/EC2 and C1s are identical. It is only the exhaust manifolds that are different, and then only to line up with the different type of mufflers. They are entirely interchangeable. The early arangement was intended to keep all the parts under armour. When it was decided that access for maintainence and better (bigger) aircleaners were more importaint the latter design was adopted. Although it happened at the same time as the change from EC2 to C1 it need not have done though as the C1s were supplied with the later manifolds it was obviously better to make the change then.

David