XK120 SE with matching number C-type head?

Hello sirs,
i have recently seen a december 1952 XK120 SE OTS, every number matches the Heritage and ID plate, the head is a C tyoe casted C7707, no C letter near sparks, is it possible that was originally fitted?
How many cars has been fitted with factory C type head?
Thanks to all of you for your help.
Kind regards


The “Special Equipment” version of the XK 120 did not use the “C type” head: only the XK 140 SE version had the newly developed “C type” head fitted as standard from the factory.
From April 1953 onward a customer could order a “C-type head” as an option, but I understand that there were only a few XK 120’s that ever had this head fitted ex factory.
So your 1952 XK 120 cannot have a C-type head fitted by the factory, but it might be a later addition.

However, if it is a C.7707 cylinder head, it might also have been taken from an early XK 140 SE and fitted on this 1952 engine. These early XK 140 heads didn’t have the “C” cast in the head and also didn’t have the red paint.

Have you actually seen the engine number stamped on the inner front side of the head? See photo below for the position of the (fictive) number whereby the S refers to the SE execution of the December 1952 XK 120 you’ve seen

Be prudent: some cylinder heads have been stamped with a new number to match the block… Normally a 1952 engine should have an engine number starting with the letter W whereas the XK 140 C type heads had an engine number starting with the letter “G”.

Logical next question: do the block and the head have the same engine number?

Bob K.

Hi Bob,
block and head have same number obviously.
The car was despatched mid december 1952, the head casting is C7707, the W engine number seems original.


You need to advise actual numbers and photos and if available a JDHT certificate of your claimed date and matching numbers. Your comments to date are far to general , and indeed as they are, it’s a definite NO.

if the XK120 is a 1952, as you claim, the C7707 C- type head did not then exist, so impossible combination. If the XK120 is a 1953 or a 1954 there is an extremely remote possibility that it may have an original factory fitted C type head, but we are still talking less than .01% possibility. Against those improbable odds, there is more chance of a deliberate, or ignorant misrepresentation.
As above, numbers and photos please, to see if it’s one of the potential 0.01% or more probably not…

I owned an OTS for 15 years, i run 5 mille miglia with it, i know many details of the model, i know how they are stamped original numbers, i know how to read Heritage and so on…
… the car was despatched 17th dec 1952, head numbers are per original specs (W68…-8S) the font are like they should be, i know that bulletin stated from march 1953 but i’m not sure of it.

This is the head number, can you spot something strange?

Well, there’s that big black blotch in the middle. :rofl:



Your W6896-8S stamping on the head may well match what number is on this cars Heritage Certificate, but you still haven’t provided any advice/photos nor proof of why you think this is a C7707 Part Number C-type Head???

I suspect you have made the old mistake of thinking that the -8S suffix automatically means this is a C-type Head, given with XK140 G-prefix Engine Numbers any -7S, -8S or -9S suffix does indicate that it is a C-type Head.

With both W and F prefix XK120 Heads, having an -7S, -8S or -9S indicates that the XK120, including its Engine has been factory built to SE (Special Equipment) specification only; it DOES NOT indicate fitment of a C-type Head.
An XK120SE head remains an A-type head that has been upgraded with high lift camshafts and valves only, and has a twin exhaust system replacing the standard single exhaust system. This produces an increase from a 160 bhp engine to one now producing 180 bhp - so still a worthwhile upgrade.

So again - why do you think that the head stamped W6896-8S is a C-type Head, and one you specifically say is a part number C7707 C-type Head.
A C7707 part number indicates that the head casting is the THIRD evolution of the ‘Competition’ head. The first was initially reserved exclusively for the factory C-type racing cars, then the second extended to standard fitment on the ‘production’ C-types plus a handful of aftermarket customer racing XK120s (not factory fitted) and the third was the C7707 that was an optional extra on XK140MC cars - not on XK120SE.

There is nothing at all relevant that this W6896-8S XK120SE head is painted RED - again something often done by those mis-identifying an XK120SE A-type head as being a C-type head just because of the -8S suffix…

Can you provide advice, preferably photos of the number stamped on top of the head spark plug valley at the rear end.
Can you also provide photos of the cast in numbers on the underside of the head, where the head casting extends over the block, on the middle part of the exhaust side, and the front end of the inlet side …

These numbers and photographic proof will 100% conclusively identify exactly what type of Head it is that you have stamped W6896-8S. I am 99.99% confident that your head will be the same normal A-type head as used on all other normal XK120SE.

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Ok seriously, numbers can be and often are faked, red paint doesn’t prove anything, so the only positive identification of a C-Type head is the casting number C7707, located on the exhaust underside between cylinders 3 & 4, like this.
XK140 C head 003

The approximate date of a head can be determined by a sequence number at the rear of the valley, like this.
XK140 C head 005

S673307 appears to have been built as a normal car with the Special Equipment option package, i.e. wire wheels, twin exhaust, stiffer torsion bars and anti-roll bar, 3/8" lift cams.

The C-Type badges on the cam covers are easily added and often were, just for fun cool bling, or to deceive an unwary buyer.

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Rob, Fabio…
Your pictured C7707 / C3 head is the THIRD evolution C-type head as fitted to XK140MC only from 1954 onwards… These C7707 / C3 heads DID NOT exist in 1952 or 1953 as per Fabios claims for his XK120 Head W6896-8S. Fabio should refer to my request for cast in numbers, as per locations advised, that will prove whether his Head is a normal XK120SE A-type head, or the exceptionally remote possibility (less than 0.01%) that he has a period 1952/3 SECOND evolution C-type head as fitted to the ‘production’ C-type racing cars and a handful only aftermarket customers racing XK120s…

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And if it is a standard A head it will most likely have the casting number C6733 somewhere on the underside, like these which happen to be at the rear on the intake side.

Incidentally, both these are 120 heads with the stamped “S” suffix.

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Specific casting aside, it does appear the head stamping is from the factory with the correct font. The red paint not so much.

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Looks like it had more red paint 8 years ago.

The Heritage Certificate does not mention a special head.

Another way to tell a C head from an A head is the intake port diameter.
The A was 1-1/2" while the C was 1-9/16".
The exhaust ports on the A were 1-15/16" while on the C they were 2".

Roger, I’m curious to know, did the second evolution of the C head have the C7707 casting number but not the letter C in the valley, or any other characteristics to differentiate it from the third evolution C head?

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You need to appreciate that referring to these ‘Competition Developed’ heads, under the generic reference C-type head is retrospective, and not totally accurate with respect to both first and second generation ‘Competition’ heads. Jaguar themselves saw fit to refer to the production standard C.7707 casting head as available as an optional extra for the XK140MC as there C3 - as per the raised cast C7707 over C3 on the exhaust side underside as per your earlier photo. I interpret this C3 as denoting the 3rd generation C-type head casting, albeit I have nothing official that spells out that my interpretation is correct, but it works for me. All the earlier Competition developed heads use a different main casting, and thus have different casting identifiers and stampings on them. I don’t give away this detail publicly, as I like to stay one or more steps ahead of the fakers and forgers such as we already get with Chassis Plates and Engine Number stampings.
But the C7707 C3 head was designed/developed to be ‘production’ volumes ready to suit its ready optional availability on XK140MC, as apposed from all the earlier competition heads that were of varying degrees of development and hours of hand working/fettling. The earliest C7707 C3 heads did not include the large cast ‘C’ in the middle of the spark plug valley, with being painted RED then being deemed enough for marketing purposes. Given apart from being painted RED, there was no easy/reday way to differentiate the extra cost/appeal/performance C-type head from the standard XK140 head, which was of course the same as the earlier XK120SE A-type head, thus with many XK120SE owners, and I dare say a few standard XK140 owners simply painting their bare aluminium heads RED for whatever their motivation was, Jaguar decided to then add the large cast ‘C’ on top of the C7707 C3 head. So nothing technical/significant changed, so still a C3 head, but at least for marketing purposes there was now a ready identifier of being a C-type head that was not so easily faked as per red paint… Heads with the added large ‘C’ were first seen from approximately G1500 (+/-100) which as you know is indeed approximate (given Engine Numbers are not in strict order), but I have narrowed down to a far more accurate HSN demarcation which is a lot more accurate and also to a more accurate CSN which I believe is 100% accurate.
Jaguar didnt see fit to change/reidentify the C7707 casting until later 1956 when a minor change to the inlet manifold stud cast holes was indicated by now having a C7707-1 casting identifier. There was no other changes of significance to the casting, thus was still identified as being the same C3.
So yes, the first 500 or so C7707 C3 heads did not have the familiar large cast “C” in the middle of the spark plug valley, thus its only the added RED paint that readily identifies/differentiates them from an XK120SE /standard XK140 A-type head, thus the many examples of added Red paint to XK120SE A-type heads as per this W6896-8S example, that if you look at the other photos on XKData of S673307 you will see that the A-type head has also been fitted with TYPE C cam cover badges so I would suggest a deliberate effort by someone in the past to misrepresent what is fitted to this XK120SE.
And if you read the July 2016 auction description, you will see why ignorant or deliberately deceptive auction houses have various legal caveats about their auction claims/descriptions accountability/liability… Buyer beware!!!

But there is still that 0.01% chance I might be wrong, although regardless this ‘numbers matching’ XK120 should not have TYPE C cam covers nor the RED paint which was not available until the first XK140MC…


Sounds like porting, what the street rodders were doing in southern California in those days.

“Just a little deuce coupe with a flathead mill,
But she’ll walk a Thunderbird like its standin’ still.
She’s ported and relieved, and she’s stroked and bored.
She’ll do a hundred and forty at the top end, floored.”