"C" head on 140 with no evidence of red paint

(Weston Keyes) #1

Hello Folks,
I am rebuilding an engine for a customer with an XK140 coupe RHD from the mid "56. There is no evidence at all that it was ever painted red. Also it was unlikely it was ever serviced and dipped in a solution that would have removed all the paint. It is a nu,bers matching car so unlikely it is not the original head. I also have a Mark VII “C” head that doesn’t have any paint on it. Does anyone have an XK 140 “C” head that isn’t painted red?

Many thanks
Wes Keyes
York, Maine

(Roger King) #2

Mine was greeny-gold when I got the car. Scratching this off revealed a very thin coat of a sort of dirty brown/red colour, but not very much at all. The head has the right numbers, the cast ‘C’ and reportedly has never been off.
As an aside to this, I have come across a ‘C’ type head that doesn’t have the cast letter ‘C’ in the valley, but the numbers are right. Did that happen, too?

(Weston Keyes) #3

Sorry folks, my first email should have said LHD not RHD, not that probably makes any difference.


(Weston Keyes) #4

Hi Roger,
Thanks for your reply. You mentioned “C” heads without the cast in “C”. I hope I am not spreading false info so take this with a grain of salt, but I think the C heads were first introduced on the 120’s and didn’t have the C cast in but were like the ones that followed that added the C.


(Roger King) #5

Thanks Wes. The head on my car is also for a LHD, and the red is pretty hard to find.
The other ‘C’ head is a 140 ‘G’ number, so I’m not sure what’s gone on there.

(Nick 53 XK120 OTS) #6

heavy sigh…no need to speculate and guess and post info that starts with “I am not sure but…” so please note that…extensive cyl head and C head data/info is in the archives, the most definitive and researched via Roger Payne…(thank you RP). from which the info will tell you that while C heads were manufactured in the 120 era, (C6527 and C7700) and available on Type C cars, and even from the factory (C7700) as replacement heads, the C head was not a factory install on the XK120. Red was on the C head when factory installed on the 140 MC, (C7707)but not prior. The letter C was not on earlier C heads…then the “C” became standard fm appx G1500 , appx January 1955, . Nore on the Dates/engine nos etc are in the archives. Nick

(Rob Reilly) #7

It helps to include the serial number, if any, stamped in front of the front spark plug.
Also the cast-in part number found on the underside, usually C7707, which will confirm that it is indeed a C head, and not a modified A head or a B head.
The competition head with improved porting and 1-5/8" exhaust valves was offered as an after-sales Special Order accessory, with or without the 2" carbs and appropriate manifold, beginning April 1953 according to Service Bulletin 95A.
At that time we believe it did not have the cast letter C in the valley, nor the red paint.XK140%20C%20head%20008
It would have been available to Mark VII racers, and in fact is listed in the Mark VII parts catalogue as a Special Order.
Service Bulletin 163 dated Feb '55 says the C head is now being painted red between the valve covers.
So the best research we have been able to conduct has led us to believe that in the XK120 era they were not painted, and in the XK140 era they were.
Valley only, including the 3 hex plugs and up to the peak, not the sides, not the front, not the back.
As to when the letter C was added, this is less clear, but seems to also be with the beginning of the XK140 era.
Other members of this forum have done more extensive research and will no doubt add to anything I have missed.
We are also interested in recording the numbers either in the middle of the valley or at the back, which help in future research.

(Sroope@aol.com) #8

Evidence exists, to support the claim that XK 120s were built and dispatched, ex factory, fitted with C Type cylinder heads. Sufficient information is now known about the castings and stampings of XK heads to identify factory replacement heads, heads fitted retrospectively or heads machined out of expected sequence or period.

My research has unearthed two West Yorkshire Foundries C Type cylinder heads, with F prefix numbers stamped, as expected, on the vertical face of the timing housing. Not G (XK140) prefix or E (C Type). Not re-stamped or tampered numbers; original XK120 factory engine number stampings. The other numbers on the head, cast by the foundry and stamped when machined by the factory, are consistent with other known C Type cylinder heads.

Always difficult to push against the weight of public opinion but the evidence that has come to light in the last year is compelling. Give me a little more time to complete my research and I’d then be please to share the finite detail.


(Lee140FHC) #9

A little more info here: My G5752-8S head came without paint that I could detect AND had NO “C” cast-in(or stamped, for that matter). Car was built in Oct., 1955.

(Terry McGrath) #10

certainly early XK140’s had a C type head but without the cast “C”
and there is the C type head on the C type and it doesn’t have a cast “C”

(Lee140FHC) #11

The point is, my engine is so late it SHOULD have had the cast-in “C”.

(Terry McGrath) #12

can you post pic of actual engine number stamping at front of head

(Roger Payne) #13

As noted, I have been researching Cylinder Heads for many years, and in particular the progression/development of the so called C-TYPE Head, and although I am now confident I can be conclusive as to their development/evolution over their June 1951 to January 1957 period of development/evolution and usage, their are indeed a couple of anomalies and loose-ends to be finalised.

I do have a comprehensive paper half written, fully describing, picturing and explaining the whole C-type head story.

A couple of relevant conclusions.

The C-TYPE head as was offered as a factory optional extra on XK140MC and a handful only Mark VII saloons was the THIRD major variant. It was Jaguar Part Number C7707, and indeed the foundry that made these castings for Jaguar, included the cast in C7707 over a C3 on the underside of the cylinder head. The C7707 casting is obvious, and the C3 is presumed to indicate the third variant of the C-type head. This C7707 over C3 is clearly shown in Rob’s photo, so no point posting another picture. The adjacent RHB527 is an internal foundry reference number, that I call the CASTING SEQUENCE NUMBER (or CSN), and incremented on at a time for each head casting made, but after many years of gathering data, is a most important number that allows the age of the casting to be approximated. This CSN started at RH10 (presumably, with RH70 being lowest number confirmed) and ran up to RHF998 (so far, being the highest number confirmed).

Now these C7707 / C3 castings did NOT initially have the very visible large cast ‘C’ in the middle of the spark plug valley (as shown in Robs third photo), with XK140s so fitted up to engine numbers from G1015-8S up to a high of G1362-8S so confirmed without the cast ‘C’.

From a low of engine number G2183-8S onwards up to a high G9763-8S, C-type heads now did (mostly) include this cast ‘C’. I am aware of the large gap between G1362 and G2183 not yet sighted/confirmed, but note that these engines are not all C-type heads, with many being A-type heads as fitted to ‘standard’ XK140s. (Certainly I would love input from anyone with a C-type head with an ENGINE NUMBER in between G1362-8S and G2183-8S)

But it must be appreciated, that these heads were sand-cast, and typically all cast in numbers/ identifiers were produced by special additional moulds, and as already noted the CSN was changed for each head casting, so they were all individually prepared moulds/castings. There has been a small batch of C-Type heads where the cast in ‘C’ is missing, and clearly never provided for in the sand-casting mould, but with an Engine Number much later than expected, thus reasonably presumed to be a mistake/error. I have been able to closely examine at least four of these, all within a close batch of CSN heads, that after machining, allocation to an Engine, and being allocated to an XK140MC all have engine numbers in the G53xx-8S to G58xx-8S range. You must appreciate however, that it is quite possible that other heads from the same CSN batch without the cast ‘C’, may end up having an Engine Number higher or lower than this range. Indeed apart from this batch with the ‘C’ mould missing, I have been advised that with a sand-casting you could also have potential one offs with a damaged or indeed filled ‘C’ mould.

Regardless - there are enough clues, and enough evidence of Casting Part Numbers, Casting Sequence Numbers (CSN), Head Sequence Numbers (HSN - the RC444 stamping in Robs 4th photo), and actual stamped in Engine Number to identify if a head is a genuine C-type head or not, and indeed its approximate age that can identify if a head is original to a particular XK140MC or not, and indeed of course, reveal the origin of the many XK120s that now have C-type heads fitted aftermarket.

The only other detail constantly debated is the RED paint.
Research to date is now so comprehensive, that it can be considered CONCLUSIVE, so let the nay-sayers prove otherwise. The XK140 Owners Handbook which was prepared prior to the XK140 launch in October 1954 clearly announces the availability of the C-type head and being identified by being painted RED. Note - no mention of the cast in ‘C’ as that wasn’t added until early 1955.

The C7707 / C3 C-type head can be considered the ‘production’ version of the C-type head, first available from the first XK140MC - so far from as early as G1015-8S and onwards, and always originally painted RED. RED paint is not permanent as is casting numbers and cast in ‘C’, so there is no surprises at all when people 60 yeras later find a C-type head with minimal or indeed no red-paint remaining. Indeed many a head has been cleaned in a chemical bath, which 100% removes any existing red paint.

The only debate is where the RED paint is applied, and again there are many opinions given the fact that 60 yeras later, there may be little signs of remaining red paint in all original areas, and indeed there is no actual reason why a head painted RED in October 1954 was still painted RED exactly the same way in January 1957.

MY conclusions based on many yeras of specifically seeking out original red painted heads is:-

  1. The entire spark-plug valley was painted RED, from the curved-edge at the front just above the engine number stamping, all the way down to the rear of the valley and indeed over to the rear of the head. The sides of the valley were painted right up to the cam-cover gasket joint, so most definitely over the machined sides - which amazingly some people mask and don’t paint.
  2. The complete rear of the head, but noting the gasket surfaces for oil pipes were not.
  3. There was NO red paint at all on the INLET side of the head.
  4. There was definitely NO red paint on the FRONT of the head.
  5. The only area of debate is the EXHAUST side, and indeed I now tend to think it did vary based on Oct 1954 to January 1957 age, and indeed maybe overlapping batches.

There is some evidence that some heads were not painted RED at all on the exhaust side.

The overwhelming majority were however painted red along the rough-cast area above the exhaust manifolds, and blending around the curve of the timing chain housing.

And a large number also had red paint on the machined strip between the front and rear manifolds, whether deliberately here, or overspray from the deliberate top strip is debateable.

Not mentioned above, but from mid/late 1956, there was a slight modification made to the C7707 / C3 C-type head casting, that warranted a new Jaguar Part Number C7707/1 that is visible now on the castings as C7707-1 / C3

And note - no comments hear about the earlier variants/developments of the C-type head as fitted standard equipment on C-type racing cars, and made available to other special order for other competition applications as per the ‘infamous’ Service Bulletin 95B.


Question about the S2 cylinder head (1969)
(Roger Payne) #14

Yours is one of the batch of genuine C-type head with the ‘C’ missing that I have mentioned.
Yours is within the Engine Number range, albeit that is not conclusive, but more importantly and relevant it is within the CSN (Casting Sequence Number) batch identified.
So I for one, have no problems at all with your C-type head NOT having a cast in ‘C’


(Nick 53 XK120 OTS) #15

Such fine information…thank you Roger, and Simon…the XK C-head world awaits detailed research that as with any such “science” will need to bear the scrutiny of peers. Fear not. Any new information based on sound and even reasonable facts is worthy of presenting. Nick

(Roger Payne) #16


The earliest C-type heads (prototypes, and what was fitted to production C-type racing cars) and other special order applications pre 1954 did NOT have any cast in ‘C’.
As per my detailed overview, the earliest ‘production’ C-type heads as readily available on production XK140MC also did not have cast ‘C’, being something EXTRA added by the foundry from early 1955 (see my advised Engine Numbers range).

But 100% NO - C-type heads were NOT introduced nor available for XK120s.
After researching this red-herring to death, there are two only, and possibly a third (and maybe a couple more at most) XK120s that have been reliably confirmed as having second-type C7700 /C2 C-type heads fitted new by the factory - and these don’t of course have the large cast ‘C’, nor indeed were they originally painted red. So there is no way of identifying these from above, in an installed engine. All XK120 Special Equipment had an Engine Number with a suffix S added. This does not mean a C-type head, and that is I am sure the source of the confusion, as the suffix S on an XK140 Head does denote a C-type head being fitted (a third variant C7707/C3 head).
NO XK120 ever got a factory fitted ‘production spec’ C7707/C3 C-type head.


(Lee140FHC) #17

Thanks, Roger…I didn’t know that there are at least 4 of these heads without the “C”…and possibly many more…a week-long foundry screw-up?

(Roger Payne) #18

I have now at least six, now confirmed, with the common identifier being the CSN indication a batch where the foundry didn’t include a ‘C’ die in their sand mould for whatever reason - presumably an oversight/omission, or maybe a failed ‘C’ die that they didn’t have a ready-at-hand spare for an imminent batch pour.

But your head, and all the details you provided some time ago, was a key example that assisted my research into this otherwise apparent anomaly.

But I do have also an isolated case where I think the ‘C’ die was in place, but either damaged or filled with loose sand! So a one-off I am sure, and not a batch example as per yours.


(Sroope@aol.com) #19


I don’t have the extensive detailed list of C Type heads Roger has but note that your head, CSN RH585, and the other G58xx head I have recorded with no ‘C’, RH436, both predate the first MC head with a cast ‘C’. The first recorded CSN of an XK14 head with a cast ‘C’ is RH792 / G1605-8S.

Does your head have a plinth and no ‘C’? Perhaps an evolution from no ‘C’ to plinth and ‘C’ or as you suggest a mess-up. But not a missing ‘C’ as the first had yet to be seen.

Whatever the reason, these few heads sat in the parts bin for a long while before being picked and machined, hence the later engine numbers.


(Rob Reilly) #20

Early in my career I was sentenced to a foundry for my sins, er I mean, employed as an industrial engineer doing time studies and counting scrap castings.
The letter C is made by a little brass tag that was nailed onto the main molding pattern at the foundry. Sort of like the brass numbers you can buy to put on your house. You can see the marks where the nail heads were on mine. The main molding pattern looks like half a head made of wood or sometimes brass. The other pattern looks like the other half of the head. An empty steel box is set on each of these patterns, filled with wet sand mixed with clay, packed down, then lifted off. The bottom is called the drag and has to be rotated as it is lifted off the pattern. The top is known as the cope and is not rotated, just set on the drag along with some cores to form the inside passages and clamped together. Then it is moved to the pouring area with a crane.
So a letter C pattern tag knocked off or a bit of dislodged clumpy sand is always a possibility. We sometimes see minor sand defects, little clumps where you think it should be reasonably smooth. Major sand defects would be rejected by the inspector and the head melted down to be reused.
I once inspected a casting that had a big lump on the side in the shape of a beer can. We knew who did it.