Over the years i’ve seen 120’s , usually around '52, that have a small strip of another data plate attached over the original plate, with different valve clearances ( .006 and .008 instead of standard .004 and .006 ). It’s only about 1/2" wide and attached at same bottom holes as the original plate under it. I’ve assumed that’s when the factory started adding the higher lift cams to some cars. Does anyone know the real reason for this add-on?
I’m asking this because i’m restoring my very early '61 E-Type (OBL) that has this strip on top of the original number plate with .006 and .008 on it like the 120’s i’ve seen. If I can find out why some 120’s put on the strip, I might have an answer to why this XKE has the added strip.
I figure the factory had a reason to do it 10 years earlier on some 120’s and that might be why my E has it too. Every other E i’ve worked on (170+) had no added strip and the usual .004 and .006 on the plate.
I was going to post this on the E-Type forum first, but I figure the XK crowd might know a bit more about this.
I am familiar with strip on the 120’s and certainly its unusual the strip over the top basically another ID plate that has been chopped need to check but maybe there was an oil change on the revised strip?
Love to see a pic of E strip this is unusual
terry
The specification for the lubrication of the front wheel hubs changed, which required a revision to all of the recommended lubricants. Clearly, this was some last minute change, or they would have just printed the data plates to reflect the change. Plates from 672027, (4/4/1952)
I’d still like to know why the clearances changed from .004 / .006 to .006 / .008 on only a few cars at that time. I keep a record of Jags i’ve worked on and only 6 of 58 120’s had that extra tag and all around 1952. Other engine numbers at the same time still used the old .004/.006. The .006/.008 add-on tag began and stopped within approx. 1 year then all had .004/.006 again.
Service Bulletins, anyone?
SB-65 Apr '50 describes timing procedure, inlet .006 and exhaust .008
SB-74 undated but Dec '50 or Jan '51 pads or biscuits range of 19 thicknesses now lettered superseding numbers.
SB-95 Jun '51 for competition 7:1 CR with 3/8" cams clearances .006 and .010, no mention of different clearances for 8:1 and 9:1 CRs
SB-95 reissued Jun '52 no changes to clearances
SB-95A Apr '53 no change to clearances
SB-95B Apr '53 no change to clearances
SB-101 Feb '52 changed clearances on Mark VII ONLY to .004 and .006 with XK120 remaining unchanged at .006 and .008
SB-102 Feb '52 same numbers from SB-101 repeated
SB-109 Sep '52 for SE models with 3/8" cams, clearances now .006 and .010
SB-117 Jan '53 referred to in SB-142 has something about cams but I am apparently missing that page.
SB-132 Sep '53 clearances for 3/8" high lift cams changed to .006 and .008, recommending dealers to change SB’s 95 and 109 accordingly. clearances for 5/16" lift cams unchanged at .004 and .006
SB-140 Jan '54 clearances on all 5/16" and 3/8" cams changed to .004 and .006; except cars used for actual competition work .006 and .010; dealers instructed to amend SBs 95, 109, 132.
No other mention of clearances after SB-140, but an interesting SB-209 Feb '57 describing holes drilled in the cam lobes opposite the peaks on Mark VIII and 2.4L to reduce tappet noise on cold startup, with instructions for dealers to do this on earlier cars if requested by customers.
ahh you beat me to it Rob…you know how I love to cite the SB: …reading them provides a little insight to the mindset at the Factory…sometimes when the writer was irritated shows thru…
the clearance changes seem to just show up without explanations, but thru the Service Bulletin series it seems there were complaints from owners about tappet clatter…SB147 re sticky exhaust " valve clatter"., sect" b…excessive tappet clearances" is the sole clue I find. Later Jaguar tried oil holes in the cam at the heel, and a profile lobe shape mod to quiet the “clatter”. For me, IMHO, since “clatter” seems to have been the issue, I choose to use the 006/008 spec as being the one the engineers selected.
Also SB 117 had an early first draft, which later seems to have been replaced, per SB142. The version I have Jan/53 must be the 2nd as it does not have the text referred to in 142.(.to delete information as to high lift camshafts.) My cc of 117 has no camshaft info. If you have no 117 at all…I can send.
BTW I particularly like in SB 144: “It should be appreciated that by fast drivin we mean maintained speeds in excess of 100mph”
There are mostly two issues of every Service Bulletin, the original UK issue as we also received in Australia shipped from the UK, but also a reissue/reprint for USA, with actual masters typed up in USA. As far as I can ascertain, USA got a ‘quantity’ (maybe only a few) of original UK Bulletins, but then copied them, and indeed localised them (quoting USD instead of GBP, and in places using American spelling rather than English) making there own roneo master, from which local volume were produced. Indeed there is clearly certain Bulletins where there were two or more different masters used that differed in type font, and layout, and indeed paper size they were printed on, but all with the same Americanised text/spelling.
And there were some Bulletins that were ‘restricted’ to UK issue only, so not sent to USA, and other Bulletins for Export or USA only, so although still issued in Coventry, were not distributed to UK Distributors and Dealerships.
For instance Service Bulletin No.74 is indeed undated with some issues, but other issues of SB.74 are clearly dated December, 1950
I will scan SB117 (one sheet, two sides) as best I can - the original is on UK ‘foolscap’ size paper, my scanner is A4 maximum - and send it direct to you. But it is a good one with five separate topics covered, four of which are XK120 related, including 'High Lift Camshafts (XK.120 Models).
If I get around to it, I may initiate a new thread on Service Bulletins, and also include not just the Jaguar factory Bulletins, but also the two separate East Coast and West Coast USA local Bulletins of which I have some, but not complete sets.
Your question seems to have been sidetracked somewhat.
My understanding is at the beginning of XK engine production, with not yet a lot of high mileage in service experience, Jaguar set the valve clearances at .006 and .008 as a balance between undesirable ‘tappet’ (or strictly speaking ‘cam’ noise) and a cautious/conservative approach to not having valve clearances close up and risk burning valves. With the XK120 roadster application, cam noise was not unreasonable.
By the time the Mark VII saloon was introduced, cam noise was considered less appropriate for an enclosed luxury saloon, thus now with greater in service experience, the recommended clearance was reduced to .004 and .006 for the Mark VII only, given its more sedate driving use. The XK120 initially remained at .006 and .008, but about a year later was also standardised on .004/.006. This remained the standard cam clearance for all models will into 1970s, until new ‘quieter’ camshaft profiles were introduced, and indeed allowed wider cam clearances.
But if car was ordered, or intended to be used for ‘racing’, or other similar spirited driving applications, then wider clearances than the standard .004/.006 was deemed circumspect, where ‘cam noise’ was not of any interest/concern. Cannot say I have seen any standard/production E-types with other than .004/.006, so can only speculate your very early 1961 may have been prepared for a special order or special customer, with abnormal usage intentions. Can you advise Car No?, or indeed do you know original owner or its early history?
Thank you for clearing that up for me on the 120’s.
I never looked into the car’s history (875051) but the previous owner thought it spent it’s early years around the Watkins Glen, New York area. That’s where I bought it. It’s well known for it’s race track back in the day and I think they even had formula races there. It’s possible it was built with .006/.008 , but the factory would add on a lot more race oriented stuff for a special order. The P.O. did put the car info on XKE Data and it was used as a reference car in Dr. Haddock’s first book along with detail photos. Other than being an early car, there’s nothing to indicate special prep.
I thought maybe when they built the heads, The “new guy” made a mistake with the gaps on a bunch of heads and that stamped strip was an easy way to cover a screw-up. (Just like back in 1952).
