Your twin H6 carburetter set up looks all fine to me, and original to your December 1950 XK120.
The F11 is indeed the date-code, not documented anywhere, but something I worked out many years ago now, and have detailed in a number of my published SU pumps and carburetters articles in XK Gazette amongst other forums.
The 11 is of course the month, 1-12, so 11 = November.
The F is the year code, starting with A=1945, so F = 1950. (For later dates, letters I and J are not used, so L = 1954 as per my earlier advice to Jordy)
So F11 = November 1950, which of course is perfect for your Dec 1950 built XK120.
And for an F11 dated XK120 H6 set-up, you should have earlier style thermo carb, and also short-neck suction chambers. The last ‘tall-neck’ suction chambers were fitted onto F3 dated H6 carbs, so March 1950, but allowing some lead time I usually work on April/May 1950 built XK120s being last of the tall-neck SUs if not yet checking actual date-code on H6.
In fact, I came across another thread where you identified F11 as being November 1950, which is spot on for my car.
Yes, mine has the early style thermo carb, and I now have nice new knurled bakelite knobs on the terminals, too. I’m glad the short neck suction chambers are correct, as I prefer the look of them, anyway.
Incidentally, when I first got the car it was almost undrivable, coughing and bucking on anything but the gentlest of accelerator use. I immediately wondered about the dashpots, and sure enough, they were completely empty of oil - problem solved!
This picture reminds me - how long should the overflow tubes from the float bowl lids be on an early 120? Mine are quite short, but I believe from looking at an SU catalogue that they come in different lengths.
Moss sells the overflow pipe part 451-250 at $16.99, used on a lot of British cars. Their pipe is 30 inches long.
For writing the JCNA XK120 judging guide, we reached a consensus that both pipes are clipped together with a single P-clip to an oil filter head mounting bolt, early cars the upper rear, and later cars the lower rear bolt.
BTW this may not be true for XK140 as a G engine I have here had them in two P-clips.
Finally had both carbs off and apart yesterday. Some numbers for Roger:
Both carb bodies have cast number 466 followed by lightly engraved 9/4 on left one, and 9/? on right one. Second engraved digit on right carb not clear, but probably same as other carb?
Left float bowl with integral thermo carb has cast number 3256LL and the right one is 1208 with MCL2 in tiny letters.
Both carb flanges are stamped F11 (Nov 1950) as previously noted.
I will post more about the condition of the carbs in my other post about surging issues at idle.
Thanks Chris, as expected F11 dated H6 carburetters will always have 4669 part number body castings, thus the cast in 466 allows the generic body casting to be machined up into various specific part number main body assemblies. For an XK120 the rear H6 body part number is 4669/4 this yours having an engraved 9/4 added to end of the cast generic 466. The front H6 is machined/assembled a little differently and has a main body assembly 4669/1, thus you will find there should be an engraved 9/1 added to rear of generic cast 466, albeit as you have found it is often so feint/indecipherable to be legible. (Only the 466 was cast, as these body castings were used for about 16 different final machined/assembled part number bodies for many other applications other than Jaguar, who only used 4669/1 and 4669/4 bodies)
So I think its a real shame when H6 carbies are restored where bead blasting (or similar) is used to clean the aluminium body, as that is sufficient to remove the etched 9/4 and etched 9/1 on the cast aluminium bodies. I now always recommend not to bead/abrasive blast but instead use a good (tested) chemical cleaner.
When you can Chris, a few photos of your F11 carbies, and their stampings/etchings would be great.
That’s really interesting (and pleasing) to know, Roger. The etched number I was unsure about fits the pattern you describe, because I thought at first it was 9/1, but then I wondered if it ought to be 9/4 to match the other body. So I decided there was doubt about that final digit. In fact, it looks as though I have 9/1 on the front carb and 9/4 on the rear one, which sounds exactly like what you would have expected to see!
I don’t intend to do any polishing on the carbs, except maybe the dashpots, so the numbers will be preserved, and I will certainly take pics when I take them off again to get the spindles done. The idle is still inclined to move up or down for no apparent reason, so getting the spindles re-bushed is a must, I think.
It occurred to me how much easier it must be to work on LHD XK120 carbs without that ruddy steering column in the way! In fact, I’m not sure how thick a heat spacer I can get in between the carbs and manifold, because of fouling issues with the rear carb’s jet assembly and the column. It will be a case of careful measuring. With the thick 12.5mm spacers and longer studs, I might still have problems with the rigid thermo tube. I know there is some adjustability because the float bowl with attached thermo carb can rotate on the banjo bolt that attaches it to the carb body, but it might swing round so far that the float bowl lid contacts the rear carb’s body. In that case one would have to look at possibly lengthening the thermo tube. Probably all too much trouble.
You mentioned that you had done a detailed paper on H6 carbs and I would be very interested to read it. Where would I be able to access a copy?
Chris, I have done a very comprehensive paper on SU H8 carburetters, published in three parts over November and December 2013, and January 2014 issues of XK GAZETTE magazine, and an equally comprehensive paper on SU Petrol Pumps in March 2011 issue of XK GAZETTE.
But not yet on SU H6 carburetters. A far more complex subject than H8 carburetters, with a draft paper probably three-quarters done, but other distractions have not allowed it to be finished yet.
Roger, I have now acquired several years of back numbers of the Gazette, and am working my way through them. I’m looking forward to reading the H8 articles, but meantime am enjoying the XK tools articles!
Well done.
If you are missing any of the H8 paper issues, I can forward .pdf scans.
Similarly, a bit earlier, I also did a paper on SU Petrol Pumps, as applicable to XKs - so the evolution of the LCS model pump.
Hi Roger please may I have a scan of your SU H 8 paper… so I can correctly restore the H 8s on my Dec 1953 build ‘Ctype’ Do you know if Midel still have any original SU linkage parts ? Thank you best wishes Godfrey
Roger, I’ve just taken some pics of numbers on my H6 carbs, as I promised to do. Hope they will be of some interest to you. I was at pains to tell Burlen Services not to blast the carb bodies, as you suggested.
Your F11 carbies look really superb Chris.
Would love a few more photos showing lots of views/detail of both carburetters and linkages, as these are an important transitional period H6 with non-vented short-necked Suction Chambers, not all that well known.
Well done on stopping the abrasive cleaning, I think ruins really nice original SUs, but now almost universal quick and esay expedient.
If you play around with a few chemical cleaners, you will get appearance back to ‘as-new’
Here are some more pics, Roger. I wonder when the non-vented short neck suction chambers started and finished? I have just noticed what looks like a small Z or 2 (Z, it appears to me) next to the base of the “chimney” on both carbs. Slightly clearer on one compared to the other.!
My car (660405) has several features that don’t seem to fit with the accepted wisdom in the parts book. The engine number is W-2604-7, but it has a C2331 block (supposed to be fitted up to W-2011) Sump C2359 (up to W-2057) Crank C2339 (early 6-bolt flywheel flange, up to W-1746) and inlet manifold C2377.
(upload://xL9mCuZsC1CktKj9uEVMfPzbkV4.jpeg)
Best I can say is the change from the original XK120 H6 carburetters with ‘Tall Neck’ Suction Chambers without ventilation rib, to your ‘Short Neck’ Suction Chambers without ventilation rib, happened in about May/June 1950 (F5/F6).
Your ‘Short Neck’ Suction Chambers without ventilation rib, were then replaced with ‘Short Neck’ Suction Chambers WITH ventilation rib from about December 1951 (G12) to Feb 1952 (H2), then stayed that way for remaining XK120 and all XK140. So three very different design and appearance XK120 SUs, that had been simplified for a long time as just ‘Tall-Neck’ or ‘Short-Neck’. When I revisit my H6 resercah project, I will tighten up on these above demarcations, but usual problem is finding reliable/original carburetters (and cars)
So really good to see your pair of F11 dated SUs in such excellent/original condition, solidly in the middle of my dating range for these SECOND variant Suction Chambers…………….
