Help with information factory 9:1 compression engine (And factory C-Type head)

I also posted this topic in the XK forum. I recently acquired a 1954 XK120 SE OTS that is a matching numbers factory original 9:1 compression car (Engine number ends with -9S). Interestingly the car has a factory installed from day 1 C-Type cylinder head (part #C7707) as well. I have contacted the Jaguar archives in New Jersey and spoke to Fred Hammond about it. Fred actually went into the hand written info from Jaguar and no luck with ownership info. I also have a heritage certificate, but again the original owner was not recorded by Max Hoffman when the car was sold new which is common. I have read and discussed with Fred at Jaguar that there were only 22 9:1 cars originally built and only 13 of those are left hand drive. My question is why were so few ordered as 9:1 compression? Were they built specifically for racing purposes? Would they have all been ordered by someone of importance for racing? or was it just an option that nobody ordered for no reason? It makes no sense and there isn’t much info about these cars. Also besides being 9:1 compression did these cars have other things done to them? Such as a lightweight flywheel, sand cast carbs, bigger valves, cams etc… Any information pertaining to these few special cars would be really great to hear so any help in shedding light on this subject would be great. Thanks so much!

attn Roger Payne…what say you…XK120…C head…and for Alex…how do you know…what makes you believe, C head factory installed from day 1?

Nick, because the serial number to my engine is stamped on the head, therefore it’s the original head to my car.

All good Nick. I have liaised direct with Alex, and am totally satisfied that his XK120 indeed has a factory original second variant C Type head. This is now the fourth one confirmed, all the second variant, but is independent of being 9:1 pistons. Of the four confirmed, three are -9S and one is -8S. Similarly -9S does not mean C Type head necessarily, with several -9S engines having A Type heads.


interestin…sometime back…the Guy Broad catalog stated they had as yet…never seen a XK120 head marked 9S…tho they did think they would have been so marked. Nick