I’m not sure if anyone else has seen this beautiful XK-120 on Bring-A-Trailer. It looks like a really nice car, but there’s a really weird comment that it has a dealer-fitted C-type head, though this is not an S-prefix chassis #, and clearly not an SE equipment car (the description is very clear about this)
Numbers indicate matching block but non-matching head # W-7368-8S, but not sure if there’s any way to validate it’s a C-type head
I thought the C-type engine was not an option on an XK-120, but have read elsewhere that it was, so I’m confused on that.
I’m not really a potential buyer, just found it interesting!
Well spotted Brandon - not a site I look at, but I have now registered and posted my first comment.
No surprises here. The claims are very carefully worded, OK. But this appears to be yet another case of an Engine Number stamping of W7368-8S, having an -8S suffix being misinterpreted as meaning a C-type head is fitted, because with later XK140MC engines Gxxxx-8S series the -8S does mean C-type head is fitted. This is a VERY COMMON misunderstanding. With an XK120 engine Wxxxx-8S or Fxxxx-8S, the -8S means the head/Engine is fitted to a Special Equipment specified car, or SE or sometimes in USA referred to as XK120M. The SE Engine is still a normal XK120 A-type head, but has high-lift cams fitted. And there are specific ways a genuine C-type Head can be identified by other than the stamped in Engine Number, which of course can be forged. The W7638-8S stamping on this head looks OK to me, but simply indicates its a replacement XK120SE A-type head, ex another XK120 that was built about four months later than the advertised ‘standard’ XK120.
And as John says, after the introduction of the XK140 in October 1954, when C-type heads were a common option on XK140MC, and on rare occasion also fitted with special option H8 carburetters, you could buy both as new Spare Parts from certain Jaguar dealerships, or a dare say ordered in by any dealership - and as said, a quick upgrade in horsepower. But in the advertised XK120s situation, the replacement head is simply another A-type head from another XK120, albeit a Special Equipment one, so most probably will have the SE upgraded high-lift camshafts, thus an extra 20 horse-power (gross-SAE).
Regardless.
Its looks like a very high standard XK120 FHC restoration.
“…“matching numbers doesn’t seem to affect these Jaguar values very much.” As it should be; IMHO, the whole “matching numbers” thing grew out of Bloomington trying to find some little nit to differentiate one perfect Vette from another.”
It’s a nice looking car… and has all Jaguar bitz. ‘Nuff for me!
Roger, you have come to exactly the same conclusion as me; the cylinder head was swapped for an SE (for better performance, or merely as a needed replacement, who know?), and through the mists of time, common misunderstanding/confusion with XK-140 it got confused with a “C” head. Really easy to do considering the XK140 “SE” included the C-type head, while the 120 “SE” did not. I perfer the M and MC designations for this reason, though I rarely see the “M” designation used for 120s.
I have a few comments on this auction, per Wiggles, I really don’t think the replacement head should be a big concern; but I know some people will assign a premium to a fully numbers matching car, and I think the potential buyer should be aware what it is. With my hybrid/oddball/hotrod XK-140 I’m no authority on originality, but the comment of a “C-Type head” was a bit of a flag. Upon further research and reflection I think the car is accurately represented “as far as it goes”, though the C-type head comment could be misleading.On the other hand, a cautious buyer will read a “reportedly it has…” comment for what it’s worth, in absence of any supporting documentation.
As a rule, I only use Factory terminology when talking about XKs, as the variations in Factory, English, Australian and American terminology can and does lead to a lot of confusion at times.
But I do like the USA terminology of XK120 and XK120M (to denote Special Equipment), but more so XK140, XK140M and XK140MC as per your ‘slip-up’. The added ‘M’ apparently denoted ‘Modified’ in USA usage - never a term used by factory, who used ‘Special Equipment’.
The factory had three levels of XK140 Specification.
A standard XK140 with a no-prefix letter 6-digit chassis number, and a no suffix letter Engine Number.
An XK140 Special Equipment, with an A prefix letter to chassis number, but still having a standard engine, no suffix letter Engine Number.
And finally, an XK140 Special Equipment with C-type Engine, now with an S prefix letter to chassis number, and now having a C-type head, a -8S usually (or rarely -7S or -9S) suffix to the Engine Number.
I know I prefer saying XK140MC than XK140 Special Equipment with C-type Engine, and if you don’t say the lot, just XK140 Special Equipment (SE) does not get the C-type head.
Here is an example of the letter C usually found in the valley on C-Type heads.
This head with improved porting and larger exhaust valves and throats was announced in Service Bulletin 95A dated April 1953 as being available for improving the performance of XK120 and Mark VII over and above the modifications described in SB95. Price 150 pounds for the head with valves, springs, cams and rocker covers (rockers? yes they really said that), 18 pounds for each 2" carb, and 6 pounds 13 shillings for the intake manifold required for them.
It can also be verified by the casting number C7707 on the underside.
Service Bulletin 95A refers to proposed availability of parts that could be purchased as after-market spare parts (and not something that could be optioned as original equipment on a new XK120), albeit evidence on the ground suggests they were only supplied to a handful of racing teams/drivers at most, primarily factory works supported teams/drivers in the UK.
The production version C-type head was only available as original equipment as an option, from the introduction of the XK140 model, and initially were painted RED to identify them as such.
The cast ‘C’ that you picture, was not included on the first racing C-types heads, nor the earliest production version XK140 C-type heads, but was added from about Feb/March 1955 onwards, (would need to check my records to be more exact), so only way you can reliably/easily identify an early C-type head from above, is by checking the stamped-in Engine Number, later C-type heads of course having this cast in ‘C’
And these production C-type heads were readily available as a new spare part, or as a second-hand part ex-XK140MC for anyone wanting to upgrade their XK120s or standard engine XK140/Mark VIIs.
As usual, a fountain of information Roger. It’s also interesting to note that in the US the “MC” was the most popular model, and the M the rarest.
My car was originally an MC (S prefix) but now equipped with an E-type 3.8, and a host of other period modifications (apparently done in the 1970s roughly). Of course it retains some of the unique M/MC bits like the aluminum wrapped boot floor tire door.
I need to check at home, but I have an original “new for 1955” Jaguar pamphlet and I was quite certain they referred to the M and MC models. This may have been a US publication, and therefore not “factory” per se, but official Jaguar nonetheless. I will have to check tonight.
Only recently I discovered anyone had ever used the M designation for an XK-120, as I had only ever seen 120s listed as SE. The M designation helps understand the difference between models, since an XK-120M is roughly equivalent to an XK-140M, and the added C designates a new feature/option for the XK-140.
I have always seen that the C stood for “competition” rather than “C-type head” although that was the primary difference. so XK-140 MC= Modified-Competition.
My primary reference for this history is the 2nd Edition Porter (I now have the 3rd but have not exhausted it), and I haven’t bothered with the minutiae in over a decade since I mostly concern myself with my own car which is so far from original that it’s not relevant other than I just enjoy the content.
If indeed the manifolds are porcelain, AND uncracked, they are either originals that have seen little use, or new ones that will soon be cracking like thin eggshells!
Interestingly the 140 had pretty excellent condition porcelain on it when we bought the car. Considering the rest of the car required complete restoration I doubt a previous owner had put on replacements.
It now has SS headers and the porcelain went off to a new owner over 10 years ago.
New to the forum here. Just to be clear, does a “S” suffix on the engine & head stamping indicate the engine is from a “SE” or “M” model? My Dad & I have a 54 xk120 with a non original drive-train. The car is not a “SE” model. The head & engine numbers are: W7903 -8S. Is this the “SE” engine? Also I believe the “W” indicates a '52 or older engine? Is this correct?
Always glad to see new folks joining us.
XK120 engines ran from W1001 to W9999 and then from F1001 to approximately F4250 or maybe a few more for spares. Judging by the monthly totals given in Porter’s book Original XK, your engine would date from mid 1953.
The -8 suffix indicates 8:1 compression ratio pistons were installed, which were the usual thing in the USA. It means you can run on regular pump gas.
The S suffix indicates higher 3/8" lift camshafts and the requisite shorter valve guides, different distributor and carb needles, and may or may not include lighter flywheel, different damper, and SE or Special Equipment cars usually had twin exhaust and other things not connected to the engine such as different torsion bars and anti-roll bar.
The “M” suffix was not used by the factory, but is the American dealers’ advertising designation meaning “modified” when this term was in common use among hot-rodders.
Matt. The -8S on an XK120 engine number means the engine is an SE and the original car fitted was an XK120SE, or in USA terms an XK120M.
Your cars ID plate will tell you what your cars original non SE engine number was.
Thanks for the replies. Since the original engine is gone, A “SE” engine would be the next best thing. The head and block numbers do match, so it is a complete unit. I’ll see if I can find some numbers on the distributor to see if it is correct for the engine. The cars ID plate does indicate a “F” prefix for the engine.
