The engine number in MK 1 S's are 9F/Sa/Y*****
Can they also be 9F/SAY/*****
I cant remember if the a is lower or upper case but im confident the / is after the Y

I have just looked through a couple of dozen engine number photos and the engines with original stampings prior to about 9FSAY 39100 all have a small (a) and 3 of these /// .



After that they went to the big (A) and 2 of these //.

Thanks for that
How many photos do you have with the / being after the Y

Not many. Just the early engines with the small a had the / after the y. More than half of the blocks getting around have been restamped and this is usually because they get decked during rebuilds. Look at the depth of the rivet holes each end. If they are deep then the stamping should be original.