[xk] XK heads C types

Having viewed over 3/4 of all the C types built including having seen a
couple of the motors sold to HWM etc my observations are

Head casting numbers as fitted to genuine C type Jaguars these do not have a
“C” cast into the vally

Q252
Q275 this is in XKC037
Q246
Q273
Q283
Q264
Q277
Q290
Q243
Q270
Q268
Q266 block no P180
Q248
Q254
Q257
Q261
Q252
Q270 although this has been hand stamped onto a C type head that has clearly
had the old engine number removed

there are a couple of N, W, T and R prefixed numbers inthe early cars and
the later cars had the D type heads usually prefixed AY

With 18 Q casting heads and probably I could find a couple of more checking
records further I reckon 33% having the Q prefix is quite a reasonable
sample and one could draw the conclusion that the average customer delivered
cars not the real early and not the factory cars and late cars the majority
had Q prefixed heads
terryDate: Fri, 11 Jan 2013 17:33:22 +1100
From: “Roger Payne” rogerpayne@bigblue.net.au
Subject: RE: [xk] XK heads

Terry - I am glad you said your GUESS, as the facts/evidence to date do not
support a few of your GUESSES.

I too have not physically verified what casting number may be cast (or
stamped) into the head fitted originally to “Production” C Type racing cars,
but the available literature theory strongly suggests they were designated
and probably/maybe marked C.6257. And as we all know, these bought in
castings from either of the two foundries used, will also have a whole raft
of other identifiers and foundry casting numbers which I don’t think anyone
is remotely close to deciphering, whether it is a Q or X or something else.

The problem with C-types now of course is we only started with a very small
number of them, and the number today that still have their original heads is
even less, let alone accessing them to verify stamped in Engine Number and
associated Jaguar Part Number cast/stamped underneath - and even then this
is not a casual 5 minute exercise, as the chances of a non-original head
being renumbered to seem original is quite high, thus would need a very
informed examination. I have found it almost impossible - well difficult

    • to verify any original H8 carburetters still fitted to their original
      host
      C-type.

So we agree there is certainly more work to be done/discovered on original
C-type racing-car heads.

Roger Payne - XK140MC OTS; E-Type 4.2 S.1 OTS; DSV8.
Canberra.

Terry (and others interested)

Presumably you are now talking about the “Casting SEQUENCE Number”, and not
the “Casting PART Number” and certainly not the (cast) Jaguar Part Number?

The “Casting Sequence Number” (not any official name, but what I call it) is
the number that on very early heads was STAMPED just forward of spark-plug
number 4, but later on C7707 (C-type) heads for instance was on the boss
right at the rear of the spark plug valley. Is this what you are saying
your Qxxx numbers are, and if so stamped forward of Plug No.4 or on a boss
at rear of valley?

The “Casting Part Number” is a bit unclear, as depending on the head, you
get all sorts of other numbers cast in, but on the underside. For instance,
a very early XK120 head that has A105 Casting Sequence Number, has under the
head also a cast number XK774 which is presumed to denote an experimental
number or something.

The cast “Jaguar Part Number” is of course what this theme was all about -
and in the above A105/ XK774 example, also under the head is the cast number
C2242 which is of course the Jaguar Part Number of the very first
type/version of the XK “A-type” head, discounting any
pre-production/experimental 6 and 4 cylinder heads.

But the question about the head as used on the C-type racing car, was is it
the part number shown in the C-Type Spare Parts Catalogue - C.6257, which is
also listed in the May 1953 MASTER PRICE LIST, or is it the later C.7707
part number of C-type heads fitted as original equipment to XK140MC from the
first XK140 so equipped, but also offered as a spare-parts supply from
April/May/or later 1953 for upgrading XK120s and Mark VIIs supplied new with
A-type heads.

This is the key to this area of doubt.

So of the 3/4 of all the C-types built including other motors sold to HWM
etc, how many had C.6257 part number and how many had C.7707 part number or
was there no Jaguar Part No at all?

AS advised - I have never seen the underside of a head that I confidently
believe is an original C-type racing-car head so don’t know, although the
theory suggests that most C-types would have a C.6257 head and probably all
of them, or maybe the last C-types got the newer C7707 casting. Your Q243
to Q290 range of numbers suggests all one batch of maybe/probably C.6257
heads (given the SPC and Price List date), so maybe the next “batch” of
C-type head castings were “revised for some reason/detail” C7707 heads.

Certainly it seems likely that the first batch of C7707 heads did not
include the cast “C” in the middle of the valley, with all known examples to
date having casting sequence numbers prior to AUxxx (earliest seen being
AQxxx), but all examples to date confirmed to HAVE this cast “C” have
casting sequence numbers AVxxx and later (up to at least BHxxx) - with the
one known exception - that being the subject of casting error mistakes
thread. (This is totally separate issue to whether C-type heads fitted
originally to XK140MC were painted RED and had cast TYPE C badges as per
Jaguar period literature, I contend 100% so painted/fitted)

Service Bulletin 95A of April 1953 advises limited availability to special
order a Cylinder Head Assembly as fitted to existing XK.120.C as Assembly
SD.1025 (without giving the Part Number of just the Head)
The June 1953 MASTER PRICE LIST allocates Part Numbers just up to and past
C.7707 but does not include (yet) actual C.7707, but this suggests part
number had been allocated but head so numbered was not yet available for
sale in June 1953, with C.6257 still listed/for sale.

If you too have not seen the underside of any of these 3/4 of all C types
built, then the position of the Qxxx casting sequence number may be a clue.
All the C.7707 heads I have looked at had their casting sequence number on a
boss at the very rear of the valley.

I don’t know where this is on a C.6257 head, but if the Qxxx Casting
Sequence Numbers are either stamped forward of spark plug No.4, or stamped
on the flat (not a boss) at the very rear of the head, then that suggests
that any head so stamped is not a C.7707 head.

This casting sequence number seems to be a very useful guide to any
evolution within castings, being production sequential - whereas Engine
Number stampings can be somewhat random picking of head castings from stock,
to then be machined/built up into a cylinder-head assembly and then its
allocation to which model Jaguar and thus Engine Number series, and thus
then sequential Engine Number stamping.

Roger Payne - XK140MC OTS; E-Type 4.2 S.1 OTS; DSV8.
Canberra.-----Original Message-----
From: owner-xk@jag-lovers.org [mailto:owner-xk@jag-lovers.org] On Behalf Of
Terry McGrath
Sent: Saturday, 12 January 2013 1:48 PM
To: xk@jag-lovers.org
Subject: [xk] XK heads C types

Having viewed over 3/4 of all the C types built including having seen a
couple of the motors sold to HWM etc my observations are

Head casting numbers as fitted to genuine C type Jaguars these do not have a

“C” cast into the vally

Q252
Q275 this is in XKC037
Q246
Q273
Q283
Q264
Q277
Q290
Q243
Q270
Q268
Q266 block no P180
Q248
Q254
Q257
Q261
Q252
Q270 although this has been hand stamped onto a C type head that has clearly

had the old engine number removed

there are a couple of N, W, T and R prefixed numbers inthe early cars and
the later cars had the D type heads usually prefixed AY

With 18 Q casting heads and probably I could find a couple of more checking
records further I reckon 33% having the Q prefix is quite a reasonable
sample and one could draw the conclusion that the average customer delivered

cars not the real early and not the factory cars and late cars the majority
had Q prefixed heads
terry

Date: Fri, 11 Jan 2013 17:33:22 +1100
From: “Roger Payne” <@Roger_Payne2>
Subject: RE: [xk] XK heads

Terry - I am glad you said your GUESS, as the facts/evidence to date do not
support a few of your GUESSES.

I too have not physically verified what casting number may be cast (or
stamped) into the head fitted originally to “Production” C Type racing cars,
but the available literature theory strongly suggests they were designated
and probably/maybe marked C.6257. And as we all know, these bought in
castings from either of the two foundries used, will also have a whole raft
of other identifiers and foundry casting numbers which I don’t think anyone
is remotely close to deciphering, whether it is a Q or X or something else.

The problem with C-types now of course is we only started with a very small
number of them, and the number today that still have their original heads is
even less, let alone accessing them to verify stamped in Engine Number and
associated Jaguar Part Number cast/stamped underneath - and even then this
is not a casual 5 minute exercise, as the chances of a non-original head
being renumbered to seem original is quite high, thus would need a very
informed examination. I have found it almost impossible - well difficult

    • to verify any original H8 carburetters still fitted to their original
      host
      C-type.

So we agree there is certainly more work to be done/discovered on original
C-type racing-car heads.

Roger Payne - XK140MC OTS; E-Type 4.2 S.1 OTS; DSV8.
Canberra.

In reply to a message from Roger Payne sent Fri 11 Jan 2013:

Roger,

And as we all know, these bought in
castings from either of the two foundries used, will also have a
whole raft
of other identifiers and foundry casting numbers which I don’t
think anyone
is remotely close to deciphering, whether it is a Q or X or
something else.

There was a discussion earlier this week amongst surviving Jaguar
personnel such as George Buck, Jim Eastick and Peter Wilson amongst
others where this topic was touched on in connection with a head I
am trying to identify. I spoke with Peter Wilson the day after and
I understand the ‘‘X’’ numbers were allocated by Jaguar rather than
the Foundry and do refer to pre-production project/prototype
numbers. I don’t know about the ‘‘Q’’ numbers which may have been
allocated by the Foundry rather than Jaguar (or people working on
their behalf such as Coventry Climax)? Some of Jaguar’s ‘‘X’’ numbers
can be found engraved into items that weren’t cast such as
camshafts. Here is an example on a prototype camshaft:

http://www.xj13.eu/xj13/x1.jpg

… and a similar ‘‘X’’ number (cast this time) into a prototype head
with additional ‘‘T3’’ marking manually added by Jaguar:

http://www.xj13.eu/xj13/x2.jpg

‘‘X’’ numbers can be cross-referenced with lists of Jaguar
drawings/specs. I shall be visiting the archive in the next few
weeks (or what little remains of documents not relegated to deep
storage in the salt mine) and hope to cross-reference the ‘‘X’’
numbers with the ‘‘C’’ Jaguar Part Numbers (as defined by Roger). For
things like C-Type heads I suspect these ‘‘X’’ numbers will tell us
rather more than ‘‘Q’’ or other ‘‘Casting Sequence’’ numbers.

Before I visit, are there any particular numbers you would like me
to search out? I suspect both Terry and Roger already have
comprehensive lists of part numbers etc but please let me know if
there are any numbers etc I can help with knowing geography may
make it difficult for you to access the records directly.–
Neville - http://www.XJ13.eu, XJ13 in-progress.
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Part numbers
As an educated guess every mechanical/engine item initially had an XK part
number allocated basically indicated the part was experimental and
eventually when it was productionised it was given a C# part number. This XK
numbering system continued right through until at least the LWT E type.
For some reason certain parts even though technically in production and
fitted to production cars still had the XK number in the casting ie the
early 120 heads, on some bellhousings and for example on early XK150 S inlet
manilfolds the 3 separate pieces the airrail and water rail ie my XK150 “S”
prototype but also many 100’s of VS engines had the XK part numbers still
cast onto them
So experimental part XK774 became C2242

There was an exercise book at the factory that listed every XK# part number
starting at
Xk1 going through into the XK2000’s things like 5 speed gearboxes, 4 valve
heads etc etc etc.

I had realised back in the late 1980’s that the casting number was an
important number on the head and have recorded them wherever possible and in
the factory records they mainly referred to heads by their casting number in
fact the way they do you would almost call it it a serial number which it
basically is. The Blocks are similarly numbered

Certainly very early and mainly Alloy cars had the casting number physically
hand stamped into the valley of the head but not always forward of Plug no
4. later it was moved to the rear of the valley of the head, the early
heads did not of
course have the plinth evident on later heads. This number was pressed into
the head presumably when it was still warm.

Briefly there are 2 ways the factory made a part it was made as the correct
part number from scratch or they took a standard production part and
modified
within the factory to become a different production production part after of
course
they would have gone through the experimental number process. Examples a D
type head is a standard C7707 head that has other machine work done to it
probably 2 inch exhaust valves the C7707 part number is then ground off and
the D type production part number hand stamped in C7986 from memory.
The same thing with the D type block.

The C type head C6257 could be nothing more than say a late XK120 head that
has machine work carried out old part number removed and the new part number
stamped into it. The Q prefix heads are all stamped at the rear of head no
plinth

G1161-8S no “C” is casting number AT# and you would expect for a car built
late
54 not to find a casting number much earlier and noting Roger’s note that
the earliest he has heard of is AQ###

I believe certain heads ie the Q batch and the D type heads generally AY###
were done in a batch and I am sure I have read somewhere that heads or it
may have been blocks were better from one foundry than another?

I have a photo of the underside of a head that shows the cast part number
C.7707
but the last 7 is in fact hand stamped onto a machined spot ie there was a
cast number there, it has been machined off and the last 7 hand stamped?

terry

Certainly it seems likely that the first batch of C7707 heads did not
include the cast “C” in the middle of the valley, with all known examples to
date having casting sequence numbers prior to AUxxx (earliest seen being
AQxxx), but all examples to date confirmed to HAVE this cast “C” have
casting sequence numbers AVxxx and later (up to at least BHxxx) - with the
one known exception - that being the subject of casting error mistakes
thread. (This is totally separate issue to whether C-type heads fitted
originally to XK140MC were painted RED and had cast TYPE C badges as per
Jaguar period literature, I contend 100% so painted/fitted)

Service Bulletin 95A of April 1953 advises limited availability to special
order a Cylinder Head Assembly as fitted to existing XK.120.C as Assembly
SD.1025 (without giving the Part Number of just the Head)
The June 1953 MASTER PRICE LIST allocates Part Numbers just up to and past
C.7707 but does not include (yet) actual C.7707, but this suggests part
number had been allocated but head so numbered was not yet available for
sale in June 1953, with C.6257 still listed/for sale.

If you too have not seen the underside of any of these 3/4 of all C types
built, then the position of the Qxxx casting sequence number may be a clue.
All the C.7707 heads I have looked at had their casting sequence number on a
boss at the very rear of the valley.

I don’t know where this is on a C.6257 head, but if the Qxxx Casting
Sequence Numbers are either stamped forward of spark plug No.4, or stamped
on the flat (not a boss) at the very rear of the head, then that suggests
that any head so stamped is not a C.7707 head.

This casting sequence number seems to be a very useful guide to any
evolution within castings, being production sequential - whereas Engine
Number stampings can be somewhat random picking of head castings from stock,
to then be machined/built up into a cylinder-head assembly and then its
allocation to which model Jaguar and thus Engine Number series, and thus
then sequential Engine Number stamping.

In reply to a message from Terry McGrath sent Sat 12 Jan 2013:

In case anyone is not clear what we are chatting about, here
is a set of numbers on a C head from an XK140.

http://www.jag-lovers.org/v.htm?1358019369

I can tell you why a cast number might be missing or ground
off. It happened at the foundry, the sand was too dry or too
wet. When the mold was pulled up from the pattern a lump of
wet sand around the number stuck to the pattern, or a lump
of dry sand was dislodged during the mold handling,
resulting in a lump where the number should have been. A guy
with a grinder might touch it up and an inspector might
stamp the number there so the customer wouldn’t reject it.

Just curiously, Terry, why do you always change the subject
line? Why not just type it the same to preserve thread
continuity? This head thread is getting to be like a figure
8 race.

the last 7 is in fact hand stamped onto a machined spot
ie there was a cast number there, it has been machined off
and the last 7 hand stamped–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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G’day Terry

There was an interesting XK cylinder head for sale on Ebay recently ( https://m.ebay.com/itm/XK140-3-4-L-Cylinder-Head ) that prompted me to revisit this and another of your older posts.

I seek to debunk your suggestion that the cylinder head serial number (not engine or casting number) at the rear of the plug valley was pressed in by the foundry. To the contrary, this number was stamped at the Jaguar factory, by machinists, when machining up/assembling the head casting into a completed cylinder head. This number is independent of the type of head casting, it is just based on a sequential allocation of all heads going through the factory cylinder head shop.

In isolation the head for sale was not particularly significant; a standard A type head (C6733), cast by the William Mills foundry, and fitted originally to an early XK 140 #G1330-8. Note the casting sequence number (synonymous with cylinder head serial number) at the rear of the head, AU797.

In my records I have details of another later William Mills A type head #G1510-8 with a higher number in the AU casting sequence, AU841. The sequence numbers of these two A type heads are 45 apart (841-797).

Also in my records is a West Yorkshire Foundries C Type head (C7707/C3) #G1362-8S with AU823 stamped on the plinth at the rear of the plug valley.

The C Type head casting sequence number falls in the middle of the range of the two A type heads. It seems inconceivable this scenario could be managed by two foundries; that numbers so finite and close together in sequence could be coordinated between the different foundries.

The casting sequence can only have been added by the machinists at the Jaguar factory; who picked and machined in small batches the different types of heads required and then assigned the next sequential number.

It would be interesting to know the evidence that supports your suggestion and hear your and the thoughts of others.

Simon
S680732

Obviously as time goes on we learn more.
Luckily I realised the significance of the numbers back in june 1978 many, many years before others came to realise the significance of the numbers so was able to assemble a large data base of these numbers. I coined the expression “Serial number”
We went through the saga as to what the numbers were actually called as others used different names ie “casting sequence number” but checking factory records even Jaguar Cars had no set name and used these 3 different names in the period
Cylinder head serial number
Cylinder head number
Cylinder head series number
So I wasn’t to far of the mark being some 8998 miles from Jaguar Cars.
Having seen a large number of these going through to the early 1960’s the later ones to me looked like they had been pressed into the aluminum casting you can see a circle around the outside of the character and sort of knowing what sort of force is required to stamp something I had assume that these were done when the casting was still warm ie recently cast when it would be a bit softer?
certainly there is no doubt the very early cars they were stamped.
So it may work out out that they were all stamped/pressed at Jaguar Cars but without further research and total proof we don’t really know of course but can only make educated guesses.
terry

see my previous post on this subject

"Terry_McGrath1Terry McGrath
Apr 24

Having realised as early as June 1978 the numbers stamped into the valley of the head though not the engine number itself and in later years the similar number stamped into the blocks and once again not the actual engine number itself meant something I coined the expression “Serial number” and had always thought due to the way the later ones appeared that it was done at the foundry as they are literally pressed in.
Going though my archives the Jaguar factory actually refer to the numbers stamped into the head either into the centre of the valley or at the extreme rear of valley as
Cylinder head serial number
Cylinder head number
Cylinder head series number
The serial number system started on at least the 2nd Alloy RHD 120 and continued through until late 60’s

When the “Straight Port” head was introduced early 1958 they started a new serial number system at A1
And for D type wide angle heads they started a serial number system at C1 the highest number I have seen is C12 from memory

Over the years I have photographed literally 100’s of these serial number stampings and it has proved invaluable to help determine cars stated to be matching numbers where it can be easily shown that the head was cast after the car was built! It is a lot harder in fact probably impossible to remove these numbers without it being obvious as opposed to the engine number on a block or head where it can be removed almost without being visible and then it gets back to the argument of what fonts the factory used to stamp the engine numbers.
terry"

Pretty optimistic claim Terry,
Although the exact significance of what I now call the Head Sequence Number wasn’t yet understood, there were a number of people, myself included, who were well aware that this number stamped into the rear of the cylinder head was unique, and significant, many years prior to your claim of 1978.
Indeed many years ago now we had a long debate about its significance, and compared to some degree data bases, albeit you certainly didn’t claim nor offer then some ’ hundreds’ of sightings, let alone photos.
When I fully explained to you, based on a fairly strong automotive production engineering background, that I had ‘determined’ that this number was something added by the Jaguar factory, within their head machining/assembly shop, thus my terminology - Head Sequence Number -, you totally disagreed with me, and advised you believed it was a casting sequence number applied by the foundry. Seems you still do.
Apart from occasionally providing detail of a few sightings, usually in some other context, you remain overly secretive re these numbers, and other head and block identifiers, as clearly you are now interested in adding to/ reinforcing this unique identifier data base - again as we have discussed privately many times, and as I have also with a number of other interested parties.
We both know an understanding of this Head Sequence Number keeps researchers one step ahead of those who choose to deceive, by restamping/ changing the readily visible/understood ENGINE NUMBER that is stamped into the front of the head on all but the very earliest XK120 heads.
If you want to contribute to the collective knowledge of what I call the HEAD SEQUENCE NUMBER (as stamped in by Jaguar during the head machining/assembly process), then if you indeed have ‘literally 100s’ of photos/sightings as you now claim, then maybe you would like to share this data direct, or indeed collectively on this site. But such data to be useful, needs to be accompanied by other head identifiers, including ENGINE NUMBER stamping, and head casting identifiers such as foundry markings, and cast in Jaguar part number.
So yes please, contribute to the collective knowledge, but PLEASE, don’t belatedly claim the significance of this extra stamped in number was your personal discovery, indeed, you still don’t agree that it is indeed a HEAD SEQUENCE NUMBER (or Serial number if you prefer) - as stamped in by Jaguar.
I usually don’t make such postings in public, but prefer to do so direct/privately, but such given your incorrect/misleading claims have been made on this forum, they need to be corrected/ rebutted immediately on same forum, otherwise the casual observer will be mislead.

always a delight to see rogers comments
interestingly on this forum or any other I have never seen any large offerings of detailed info on say head serial numbers or any other mass of info and in fact the largest single listing of head serial numbers is at the top of this posting where I list the serial number for some 19 genuine Jaguar C type car heads not “C” type heads - see below.
If I went through the 500,000 or more photos I have I belive I could come up with 500 plus photos of head serial numbers from the earliest XK120 through to the E types etc of the early 1960’s unfortunately due to location block serial numbers would probably only total 30-40.
As to how the numbers got onto the head Whilst I as I note assumed it was done at the foundry yes it could have been done at the Jaguar factory but of course there is no real proof at this point
terry

Head casting numbers as fitted to genuine C type Jaguars these do not have a
“C” cast into the valley

Q252
Q275 this is in XKC037
Q246
Q273
Q283
Q264
Q277
Q290
Q243
Q270
Q268
Q266 block no P180
Q248
Q254
Q257
Q261
Q252
Q270 although this has been hand stamped onto a C type head that has clearly
had the old engine number removed.

Terry

Refering to my findings and post yesterday I do not think the exact naming of the sequence is important but that we are talking about the same number? Stamped at the rear of the plug valley. It is stamped; identical size and font as the engine number at the front of the head. Has anybody ever questioned the factory’s stamping of the engine number? Only a fantasist might believe either was pressed in by the foundry.

In response to your claim about the date the significance of the sequence was established; I was 10 years old in 1978, so you have some years on me. However it does appear that in that time research progress has been extremely slow; 40 years is a long time to establish that the sequence number was not pressed in by the foundry.

Notwithstanding, from a collective research standpoint it would be useful not to dwell in the past and look at the present and to the future. My detailed findings on this subject were centred on three cylinder heads (all engine & casting number details in thread above). I do have numbering information for more A & C type heads that I would be pleased to share. I suspect however this sharing will not be reciprocal; as my previous post about XK 120 9:1 CR cars proved.

Regards
Simon

simon,
back in the 1970’s and 80’s information resources were limited and my assumption based on a little knowledge that each head cast had some initial identifying feature ie a number was I would have thought reasonable, additionally the later heads to me it looked like they had been pressed in which required a great deal of pressure and that is why I assumed it was done when head was still warm ie at the foundry. It is not uncommon for a foundry to cast in or mark items they make as part of a quality control process. ie early alloy 120 blocks have the date they were cast cast into them and whilst this was discontinued it was reintroduced in the very early 1960’s
Your research reference the numbers is the sort of research that will probably determine the exact situation.
You raise another interesting point claiming that the font stamped/pressed into rear of the valley is the same font as the engine number stamped on the vertical face at the front of the head an item I have never checked and will look at this.
Whilst I actively keep a note and photograph all these things when the opportunity arises I actually have greater interests in collecting histories of SS Jaguars, XK Jaguars, Coachbuilt Jaguars, C D XKSS and Lwt E types etc and many other items including the history of motor racing in Australia etc in addition to restoring some 8 or so XK’s so so numbers stamped on a head are not my greatest concern.
It was in 1991 that I noted to various UK persons that I believed that there was a problem with the history of XKC011 and it took until 2016 to finally prove the point that XKC011 was not in fact XKC011 but was chassis number XKC047 so these things don’t happen overnite
terry

Terry,

Let’s not deviate from the point of this thread, that XK (not SS or E Type) head sequence numbers were not pressed in by the foundry but stamped, at the factory.

Unlike you, I only have a limited interest in racing in Australia, other Jaguar marques and no interest in writing and selling Jaguar books or restoring and selling Jaguar cars or parts. I don’t need to be putting my name about to further my concerns; my research is based on best endeavours and my findings and source data are available to all.

I feel we are also having the same conversation we had a few years ago on this forum (Aug 2014); when discussing factual errors in the XK 120 Explored book. I felt (and still do) it was misleading to publish detail that was a personal belief, not fully supported with evidence and you said it was acceptable. Here we are again; but as long as the wider audience are aware then I’m happy.

I attended a talk by Sir Tim Berners-Lee recently. The reason the world wide web has grown exponentially was his willingness to relinquish the credit and share his work. Had he been an employee of a large company (say IBM) who had wanted to keep his work under wraps and squeeze every last penny/cent from his idea then the technology we now all take for granted wouldn’t exist. It’s a shame we can’t follow this model and share information on this excellent forum.

Simon

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As before Terry, quoting a whole lot of Head Sequence Numbers in isolation, with no parallel detail of stamped in ENGINE NUMBER, as well as casting identifiers of whether WM or WYF foundry, and the respective foundry added cast-in Jaguar part number, and in the case of WYF foundry, their CASTING SEQUENCE NUMBER, really doesn’t tell us much at all.
Maybe that’s why you hadn’t worked out the significance of the HSN, being Jaguar added, rather than you presuming it was foundry added. But as per the previous post, how do you reconcile the two foundries having intermixed HSNs, and indeed the different Jaguar Part Number and sub-part number heads having intermixed HSNs. The only explanation, is that the Jaguar factory added the HSN during the head machining/assembly process, and indeed a look at a couple spoilt/unfinished heads supports that.
Your listing of Q prefix HSNs, as you advise all belonging to C-type car cylinder heads is useful, but again needs also advise of all the vaious other casting numbers to make much sense out of it, given the C type head casting had a number of iterations, and we’re not all the same, as just quoting their HSN in isolation infers.
Can you provide associated ENGINE NUMBERS and casting numbers.

Terry,

A few comments about your list of cylinder heads, seen in C Type cars, that have Q prefix sequence numbers stamped at the rear of the plug valley.

You say in your posts on the subject “I list the serial number for some 19 genuine Jaguar C type car heads not ‘C’ type heads”. However, the list is only 18 long and has two duplicates (Q252 & Q270); so 16 in total.

I too have seen Q264 (E1042-8, XKC042) & Q275 (E1038-8, XKC037) and also a number of other XKC cars that had later fitment heads, with the ‘C’ cast in the plug well. Not on your list is Q258 / E1006-8 fitted originally, but not currently, to XKC004; which I forwarded you details and photos a couple of years ago.

Your list is informative, but to be of use needs advice of the various other cast and stamped numbers and characteristic features of the heads. Listing the Q prefix numbers gives us no more than just that; a list of 16 numbers with Q prefixes.

I suspect it will only ever be a list; as the additional detail sought now is the same as asked when you first submitted the list to the forum in January 2013. Despite your emphatic claim I suggest you do not have the underlying data and is why you have twice withdrawn from the thread, each time not offering the information. As with much of what is discussed on this forum, ‘The devil is in the detail’.

Simon

Hi
Interesting and informative article. Thanks for your great effort!

Are there any other ways of identifying a C Type head please? Valve sizes etc?

Would C7707 (C3) with RH502 indicate possibility of a C type head on an XK140? Both being cast, not stamped. In your thread you mentioned R prefix?

Thank you…

Search on the lister, “Roger Payne”: he has posted many informative threads about XK heads.

Yes, C7707 is certainly a C-type head, take a look at this set of photos.
http://www.jag-lovers.org/snaps/snap_view.php3?id=1358019369&n4=

the number stamped in my 034 head is R337

Sean,

The easiest way to identify a genuine C-type Head is by the cast in numbers and the stamped in numbers actually on the head, some are readily visible if on top of the head, the others not so easy being on the underside of the head, but at least can be seen as they are on head casting area that overlaps the head gasket joint. Things like valve sizes and indeed port diameter and shape are not easily seen/measured and indeed 65 years later may have been modified anyway.

There were actually THREE main versions of what we now call the C-type head, with only the third version readily available and indeed commonly optioned as original equipment on XK140MC and very rarely optioned on the contemporary saloon, the Mark VIIM from October 1954 onwards. The first two versions made prior to October 1954 were not readily available, being fitted as original equipment on the racing C-type Jaguar only, but an extremely limited number of the second version C-type head were also sold (1952 to 1954) to ‘selected customers’ as spare parts for those racing their XK120s, with all spare-parts C-type heads sold after October 1954 being the third version.

You identify your head as having C7707 over C3 cast in on the underside.
This is of course a ‘C-type’ head Jaguar Part Number C7707, and the C3 denotes being indeed the third version ‘production’ head as was fitted original equipment on XK140MC.
The RH502 is what I call the Casting Sequence Number (CSN) which amongst all my other data gives a good indication of when this cylinder head was cast by the factory. (The stamped in numbers give a better idea when the casting was machined up and assembled, and actually fitted originally to an XK140MC).

It should be appreciated also that although MOST C7707 over C3 C-type heads had a large cast ‘C’ added to the middle of the sparking-plug valley/surface of the head, not all did, and indeed your CSN RH502 is most probably one of these without the large cast ‘C’.

You may like to confirm your head details with a few photos showing both cast in, and stampede in numbers on both the underside and top side of your head.

Roger

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Godfrey,

Your stamped in R337 number is what I call the Head Sequence Number (HSN) and was stamped in by the Jaguar factory as they machined up and assembled a completed head, regardless of whether the head casting was an A-type Head or a C-type head or indeed regardless of which version A type or C type head casting. So this R337 does not tell you what sort of head you have, but regardless of type of head when considered amongst other data I have built up, does give you some indication of likely date head was machined-up/assembled, and thus some better idea of what version A type or C-type head it will most likely be.
To conclusively identify exactly what a particular head is, you need both the cast in and any stamped in letters/numbers on the underside surfaces of the head, with the stamped in Engine Number and stamped in HSN on the top side of the head both reinforcing identification and also the best identifier of the age of the completed head and its original factory usage/allocation whether original to a particular Chassis Number car, a replacement head for a car, or indeed a spare head to be sold aftermarket for some buyer to use as they see fit.

Roger

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