There were actually 3 boxes fitted, the 20.3:1 C14845 was fitted to all Mk2's except by special order a 17.6:1 C8927 or also to special order a 15.7:1 C12212 box.

Interestingly, the early Mk1 had the C8927 17.6:1 fitted and then later Mk1's had C14845 20.3:1 , with the C12212 15.7:1 as special order.

All the boxes shared many parts, the primary difference was the worm drive and main nut which runs on the worm drive.

Yes the vent is inside that angled fillet, there is a hole that runs from a little below the thread for the damper to inside the chamber.

 

Homer,
I'm late to the party, but I love what you have achieved.

Definitely a Special Car.

Mike

 

I think the Cornish? grey exterior and the 1 off light green interior colour combo works perfectly. Looks ace

 

I've had a bit of time to look at the car this morning and have checked the following:

Plugs cleaned and gaps set at 25thou (were previously around 28-30)
Checked vacuum advance is moving and not stuck (can suck on pipe and make it move).
Checked timing
Checked vents in carb dashpots (cleaned out with pipe cleaner but nothing came out)
Checked carb dash pot pistons are free to rise and fall.

I took it our for a spin and its generally fine but every now and then if you accelerate quickly (say 0-35MPH foot to the floor), then stop and try to do it again it backfires through the carbs as soon as you put your foot on the throttle (even if only gently), it then does this for the next minute or so and the goes back to normal. Its not consistent as you can do the acceleration test several times in quick succession and its fine and then it will be a problem or it can do it the first time you try the test.

To me it seems that either:

1. The distributor is advancing and then getting stuck causing it to fire at the wrong time, although its fine if you let it idle which would seem to discount this.

2. The fuel supply is not sufficient and the mixture is therefore too weak when you try accelerating, how long would it take at full throttle to empty the carb floats and fuel filter to a point where the mixture goes week if the pump wasn't working/was lazy? I'm only accelerating hard for a few seconds as the 0-35 time on the car is obviously very low. I had forgotten how fast these cars are, especially when you think about what else was on the road when they were new!

3. One of the electrical components is faulty and doesn't like the sudden load put on it.

I've also adjusted the manual steering box, you can alter the end float on the shaft which is connected to the steering mechanism (i.e. not the one to the steering column) with the box in the car.

All you need to do for this is remove the centre plug, take out the spring, undo the locknut and then screw the centre section in by hand until it touches the shaft, then reassemble. I found it easier to do by taking out the oil filler lug as well.

adjusting the other shaft (the one connected to the column) requires the steering box removing and shims removing

Having done this the slight knocking noise from the steering appears to have gone, its a bit more responsive but I think the thing that I find difficult is the low gearing requires you to move the steering wheel much further than I'm used to on my modern car and other classic cars such as my Mini's and AH Sprite. I notice a company called ICS are offering a low geared worm and nut but when I contacted them they aren't able to supply at the moment.

If I found a low ratio box would the worm and nut be likely to be worn or is just the shaft end float that usually requires adjustment? Is there anyway I can check when looking at a box? I'm keen to avoid a rack and pinion conversion as I want to keep the car as original as possible whilst being happy to use it.

 

Thanks, the colour of the car is Pearl Grey and the interior is grey according to the heritage certificate but it looks more green to me, I had the colour matched to a piece of vinyl and a piece of leather that had been hidden from view and hence the sunlight wouldn't have affected them (although to be honest the colour was pretty much consistent across everything, seats, door cards, vinyl trim etc. whether hidden or not.

The colour was matched by these guys:

Spray Paint For Leather & Vinyl | Kolorbond

And I used a small Fastmover spray gun to put it on, its amazing stuff as it really seems to cover well and after three coats the colour is all good, I haven't used it much but so far the colour seems really stuck on and doesn't seem to be wearing or rubbing off which is what I expected it to do TBH.

Its not cheap and I used around 3 litres but it was still less than £150 for everything including the cleaner and prep fluid.

If anyone has door cards, seats etc. that are in good condition but discoloured then this stuff works miracles.

 

One other thing I have noticed is that you get a vibration when pulling away and when the gearbox changes into second. I'm not sure if this is a fault with the gearbox or torque converter, I will have to have a read of the manual.

I know you can remove the gearbox without taking the engine out (having done this on my 1966 S-Type) but I seem to recall you might not be able to get the bell housing off and hence the torque converter without pulling the engine, anyone know any different to this?

 

Homer,

Many years ago I had a 2.4Mk 2, which had a similar problem. In my case, the mechanical advance & retatd on the distributor was “sticky” due to a lack of lubrication. My cure was to remove the rotor arm, and beneath that was a little felt pad, which should receive a little drop of engine oil. This enables the shaft holding the rotor arm to rotate around the central shaft, giving mechanical advance/retard to the ignition.
If you remove the distributor cap and. Grasp the rotor arm, you should be able to feel it move smoothly about its central shaft. If it is in any way sticky, it needs lubricating. I appreciate you’ve confirmed the vacuum operate advance is operating, but it may be the mechanical advance isn’t.
Good luck!

 

A thought re backfire, have you checked the valve clearances, if one ore more inlet valves are a little too tight <4 thou you may have effect of an open inlet valve allowing ignition of the fuel/air mixture in the inlet manifold, a tight valve will be highlighted at higher revs, and when you put you foot back down and the vac timing advances it may be just enough to cause the backfire.

Can you replicate this with the bonnet up and car stationary ? If so you could see if the filter glass empties, but one would expect issues when under load like going uphill.

 

I have recently removed the engine from my ‘S’ leaving the transmission and torque convertor in place. I cannot see any reason that you should not be able to remove the bellhousing, with torque convertor and turns from below.
I would go it’s the sticky advance mechanism. When I purchased my first ‘S’ the advance was frozen.

 

Re Sticky Advance, my thoughts are that the problem would show on deceleration rather than when the pedal is pushed after initial deceleration so (re-acceleration) , the symptoms only occur after hard(ish) acceleration, then taking the foot off the gas and reapplying.
For some reason either the inlet valves are still open late, the fuel is lean at only that point or the ignition is advanced but again only on those conditions.

It is not an obvious one, but that is why I was looking at possible tight valve clearances, as they would be more prevalent at higher revs but again not convinced as that should also give symptoms at higher revs and not just on re-acceleration.

I would like to do a leak down test to rule out valves etc. and also look at the vacuum at the point the issues occur to try and diagnose the issue.

 

Thanks for the response, as the problem is intermittent presumably a valve issue wouldn't necessarily show up during a compression test? (I don't have a leak down tester). When I rebuilt the engine it had new valves and guides and they were all lapped in and I tested them by putting petrol in each chamber, covering it and leaving it and checking that it hadn't lost any overnight.

The valve clearances were all set to 4thou inlet 6thou outlet +/- 1thou which seemed to be the recommended tolerance reading various threads. I didn't keep an exact record of what they were.

With the distributor I did strip and rebuild this and all the parts, weights etc. were free, I will take this apart and have another look.

The speed with which the fault comes and goes does sound to me like the distributor or something electrical, its not so fast that its a momentary stutter but not so long that you would think it had run out of petrol. Its a strange one!

 

The guy who did all the machine work on my engine and builds these for race use recommended 6 thou and 8 thou, if the inlet were say 4 thou -1 and bedded in by a thou it could be now as little as 2 thou which is really too tight, it would be worth a quick check to see what the clearances are at the moment.

Compression test won't show up a small valve leak, leak down will, but the issue only arises at higher revs hence rather than a leak as such, just the valve shutting a little late with higher engine speed and advanced timing.

Strange indeed, can you get it to happen by revving the engine with no load so you could do it stationary with the bonnet up ?

 

I think i've solved it, I stripped the distributor down and found that the centre piece which attaches to the weights was tight on the spindle, a quick spray with some WD40, a clean and a tiny bit of oil and its lovely and free and I have taken the car out and so far it seems to be behaving itself. I just need to recheck the timing as I may have upset it when I had the distributor out.

 

Good to hear you found a problem, fingers crossed its solved the fault.

 

That's great, also very interesting, I would have expected that to have caused the issues more often, so good info, I will try and store that in my failing memory bank.

 

I had a chat with G Whitehouse Autos who are experts in this type of gearbox, he advised that in his opinion (and without seeing the car) the issue sounded more like propshaft.

I jacked it up, put the rear axle on stands and checked the alignment using the method in the haynes manual and the alignment was way out. I had to take all the shims out and its still not quite as its should be but on the road the problem has completely disappeared.

It does seem an odd way to align the propshaft as the result will change depending upon how much fuel the car has in the tank, how old the springs are etc.

One other thing that they G Whitehouse autos advised is that the gearbox should start in first not in second, apparently the original workshop manual is wrong in this respect as the gearboxes that started in second were never fitted to Jaguars.

My gearbox however only starts in second and I have checked that the kick down lever is right back as instructed but it still only starts in second. The car drives fine like this but I would like it to work properly so some more investigation will be required.

 

I've been sorting out a few niggles one of which was the interior mirror, the silvering has started to fail and new or good second hand ones are going for an arm and a leg.

After missing a few on ebay which went for over £90 I found a thread on a forum where a guy had replaced just the glass in his TR6 mirror by getting a piece or mirror cut from his local domestic glass supplier (which just so happens to be round the corner from me!).

£4 later and I had a lovely new piece cut to shape, only problem is that the original glass is 2mm at the bottom edge and at least 4mm at the top edge, I can't see why this would be or what effect it would have?

My new piece was 2mm and I gently squeezed the mirror surround by hand to grip it tightly.

Comparing the two in the car (by putting the old glass in front of the new one) I don't have any wider view with the old glass so its not like it would be if it were concave or convex?

I need to try it on the road but initial thoughts are that you can't tell the difference and its a damn side cheaper than a replacement.

I do have a spare one somewhere that needs a glass so if I dig it out I might have one to sell as well!

Thanks go to The Glasshouse in Redditch, they even did it while I waited!

 

Is it possible you originally had a form of “dipping” mirror, whereby you could move a lever across, and alter the angle of the mirror within it’s frame, and so reduce the glare from following headlights?
I believe they work by using a form of prism, rather than just a “flat” mirror. That may explain the difference in dimensions (thickness) in the original mirror compared to a simple, flat reflecting mirror. Something to reflect on!

 

Thanks Richard, that makes sense, I will keep my eye out for a proper mirror then but in the meantime my £4 replacement should be ok.

 

Double post