Ahhh. Now we might be getting somewhere. My cars all have the vernier adjustment. Perhaps you may have a similar but different Lucas distributor? I will post a picture of my distributor tonight, to help compare. I expect that your Series 2 should be similar to my Series 1? Paul.
Hereâs an update. The mobile mechanic came and yes, he did know about points! It took him a little while to understand the problem and with a 1/4â socket drive (which I donât possess) and a knuckle joint and many miss-steps he managed to get the distributor bolted back roughly where itâs supposed to be. It was very lumpy on 8 degrees at tick over so we backed it off to around 4 degrees and the tick over improved. As I was paying him by the hour I figured that I can now work on it myself as I now have adjustment either way on the elongated hole. After he had gone I went for a quick drive round the block and Iâm back where I started with a flat spot on the first part of the throttle travel.
I think that I will adjust the timing back to 8 degrees and fatten the mixture a little as a first step in eradicating the flat spot and see how that goes as I do have trust in the marks on the flywheel after my earlier investigations.
The mechanic used to work on race cars and was an older guy (but not as old as me!) and I can now see what I need to do.
Any other advice?
Okay a further update. Thank you Frank in particular because when I reset the timing to the 8 degree mark and fattened the mixture by degrees (at least 1.5 turns in total) hey presto! She now runs like a sewing machine. I did set the mixture originally using colour tune but obviously I must have leaned it out too much. What a learning curve this has been been (and expensive!) but I have learned a heck of a lot through this process because the spark plugs did tell me the correct story before I did colour tune - they looked perfect which I should have paid heed to as I am a great believer in reading spark plugs. Anyway, thanks a lot guys, Iâm back in love with my XJ6!
That elongated functions the same way as the vernier, RobertâŠsort of. Bolting the pinchplate to the engine in the mid-position - then loosening the pinch bolt allows you to turn the dist itself inside the pinchplate to the correct timing. Tightening the pinchbolt locks the dist to the pinchplate - which can now be used for fine tuning by loosening the bolting to the engine. Not as easy as with the vernier - but markings on the pinchplate relative to its engine bolting give easy references when âexperimentingâ with ign timing⊠PhewâŠ
As an aside; the Colortune requires some interpretation in use, Robert. The carbs are too crude to maintain ideal mixture with varying throttle settings, rpms and loads - in dynamic situations; the mixture is bound to lean out, creating occasional flat-spots. Hence the mixture is set deliberately âfatâ when adjusting in idle - reflected in specified CO levels. Which is a bit difficult using Colortune. The xk engine doesnât mind running fat - but it takes a dim view on lean feedingâŠ
You have done well - and deserve credit!
Frank
xj6 85 Sov Europe (UK/NZ)
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Frank, I have only owned the car 6 months and I have to admit that I have come a long way in that time but it still feels like it would take a lifetime to become proficient with the XK engine! My only previous experience with car mechanics was when I was a teenager and into my early 20s I suppose, when I owned a variety of mainly British Leyland cars and in those days I couldnât afford to take them into a garage, but these were very basic cars compared to the XJ6 and relatively simple (although I got plenty of things wrong when I was tinkering with them too). I bought this car as a retirement hobby not fully realising the complexity of the car but in the main I am enjoying the experience but I couldnât do it without the fund of knowledge on this site thatâs for sure. Thanks to all.
Great job, Robert!
In fact, a SII XJ is not that far away from a Triumph Herald Vitesse construction wise ⊠just that everything is heavier, more complicated and made from better parts âŠ
But maybe you should get back to square one - even with the current problem solved: What is your engine number? Are you below 8L.16710? If so, does your distributor look like in the picture? Do you have the original clamp with the pinch bolt?
Frankly, I still fail to understand how you moved the distributor away, as its general position is determined by the shaft as I understand it. In its natural position it can be rotated. So is that possible now or did you simply go back to the original position?
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Hi Jochen, effectively I believe that the timing is back where we started at 8 degrees BTDC. My problem was that I managed to undo the pinch bolt and rotate the distributor, but the pinch plate rotated with the distributor partly because I hadnât slackened the bolt sufficiently and then the bolt became inaccessible and I couldnât tighten it up again.
I am now working on getting the mixture spot on although I am thinking of leaving that well alone as the engine is running sweetly (at the moment) and one of the many lessons that I have learned over the past little while is âif it isnât broken, donât fix itâ!
My engine number is 7L 82393. The distributor looks very much like the one in the picture but the plate that it sits on is different. The plate looks original and doesnât have the feel of anything home made but did it come from another car? No way of knowing.
Just added a photo of my engine, far from immaculate but if you saw what I started with!
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Looks great!!
Jeff H
You are doing great, Robert!
I was 9 years old when my father put me on the first job; straightening the valve rods on his 23 Buick - with hammer and anvil. Bent at the first turn of the engine after storage throughout the war. My father was ingenious in making things work - âfind a way or make oneâ - which in Norway at the time was dire necessity; he taught me a lot!
Frank
xj6 85 Sov Europe (UK/NZ)
**
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Necessity is the mother of invention Frank!
Hi Jochen,
I have just ordered a new rotor arm from the company that Paul recommended (Distributor Doctors) and after some discussion by email they inform me that I have a 45D6 distributor. I guess that itâs good to know these details for future reference.
Could have found a Model T Ford. Few tools needed to deal with any part of it.
Carl
Wow, Robert,
that looks just great! I can imagine the labor of love it must have been to look that good!
Then again, it tells a story making your distributor setup kind of fall into place as there are quite a number of obvious parts not in line with the good book ⊠most obviously, someone has done away with the air duct over the head supplying the intake and making sure the carbs only find air at 40°C. The expansion tank has been replaced by a generic part. The cut-off switch at the battery box looks a very clean job (I even omitted the battery box as itâs very hard to find good batteries fitting inside the box and sitting high enough to give access to the clamps. Most surprisingly, I canât see any cold start enrichment device. There should be an aux carb between the two SU carbs - even if the black bakelite cover of the automatic control device is lacking there is usually a prominent cable driven brass cam shaft operating the fuel and air valves. How is your cold start enrichment operated? I seem to spot a kind of bracket that might operate on the jets and raise them. Keith Turner has occasionally described how a âcarbs onlyâ enrichment can be done on HS8s.
With your engine no. there should be the older distributor. Never mind. The Lucas 45D6 is fine. Does it look like that?
You can see the clamp with the pinch bolt integrated in the lower part. The ROM has identical procedures for timing as you already followed. - I canât quite see though what the bracket C.44456 is good for.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Hi Jochen, I have attached a few more photos of my engine. There are quite a number of non standard features as you will see. The AED was removed by a PO and has been replaced by a home made cable operated choke which actually seems to work okay. It depresses the parts on the carbs that you use to adjust the mixture, I have added a small âcamâ on the end of the rod that slightly increases the tick over on one carb just to assist with tick over when cold. I can only assume that the AED was giving issues.
I have to admit to not realising that there is an air duct missing altogether! I do have this âtrumpetâ on the next photo but Iâm guessing that you mean something different?
The diagram that you have put on of the distributor is exactly what I have except it doesnât have the elongated hole to make minor adjustments to the timing. Would this have been a replacement part from the original?
And finally the other major difference under my bonnet is the exhaust manifold/header
Of course when you purchase a car like this you also purchase 46 years of history and when youâre not even sure what it is supposed to look like, well you just accept things as they are.
Robert,
originality for its own sake is for purists or people who invest and fear losses.
I do have a penchant for originality, but only for pragmatic reasons: it makes troubleshooting so much easier!
What I see on your car is far from original, but it makes a lot of sense to me. Whoever did that knew very well what he was doing. The replacement of the aux carb looks very clean and the headers are plain gorgeous.
In stock version there is a stainless heat shield over the headers (protecting also the hood, aka bonnet) and collecting hot air to be taken through a black duct ending in a two-inch hose leading to the hole in your intake box.
Brownâs Lane intended that cold air was picked up by the trumpet on the front cross brace before the radiator and taken in, then blended with said hot air from the duct to always have 40°C. To this purpose there is a t-stat and a vacuum operated valve at the air filter box. Your last pic shows one of the holes where the air duct is bolted to the valve cover.
As for the distributor I donât have any idea why someone would change the clamp. Then again: the clamp in your pic in post 15 clearly has the longish hole to allow for the fine tuning; it looks fairly like the one in the diagram. The question remains though why you cannot rotate the distributor after loosening the pinch bolt. Have you tried to lever open the clamp upon undoing the pinch bolt?
Enjoy this beautiful car!
Jochen
75 XJ6L 4.2 auto (UK spec)
Hi Jochen, well that photo of your engine bay told a thousand words, I have seen this part across the top of the head on other photos but I didnât think that it was for air intake. I would have thought that the air going into the engine would be better as cold as possible, or do my physics let me down here?
When I saw your photo I went and had a closer look and this is what I found over the intake to the carbs
Itâs the top from an aerosol can painted black! Underneath is a spring loaded hatch (sprung closed).
I went for a reasonable drive this afternoon (lovely day in Auckland) and Iâve just removed the spark plugs and they look perfect, just the right light chocolate colour and the engine will now tick over at a steady 700 rpm in P or N, it has never done that before. Very happy, I wonder how long it will last? 
The trick now is to leave it alone.
Started work today on cleaning the recesses around the wheel arches, not even any surface rust.
Thanks again all
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The choke function must do two things, Robert; fattening the mixture to compensate for less efficient carburation when cold - and to increase idle to compensate for cold engine drag, friction. Ie, a âfast idle camâ is not there to ââŠassist with tick-overâ - itâs a vital starting aid with a cold engine. More power is required from the engine to overcome initial drag, which means higher rpms, which means higher rpms. Some 200 - 400 rpms above hot set idleâŠ
The original AED did this automatically, but when failing; a PO obviously decided on a different approach. Which is perfectly feasible - cannot argue with success! So if you have no problems with cold startingâŠ
Frank
xj6 85 Sov Europe (UK/NZ)
**
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Will we see the car at the British and European car show in 7th March 2021, Lloyd Elsmore park?
Hi Robin, I havenât thought of it to be honest, not sure that my car would be good enough to show to a discerning audience!
Robert,
the purpose of the air duct and the considerable technical effort involved was to allow for a tuning of the carbs as perfectly as possible by eliminating one variable: the temperature of the air.
Cold air will be richer in oxygen and thus allow to burn more fuel, but in a real world it is always possible to add more air to compensate for a lower content of oxygen.
Thatâs why the t-stat and the valve are aimed to maintain an intake air temp of 40°C. Only hot desert regions would exceed that kind of ambient temperatures. Usually, the intake air would be pre-heated to always the same 40°C and the carbs are tuned to exactly that kind of intake air.
Doing away with the air duct is no big deal and doesnât hurt the engine, but tuning carbs will be a compromise: do it at 20°C in a workshop and the engine will run richer at ambient temps below that and leaner at ambient temps above - a bit risky maybe, if you challenge the car maybe by going into the mountains on a hot day âŠ
And, yes, go to the meet - maybe not (yet) to be adored, but at least to be inspired!
Have a nice Sunday
Jochen