The original timing sprocket supporting plate for my 140 engine has a large lower section, with bolt holes to attach to the block. The shaft that the intermediate sprocket runs on was worn, so I bought a later timing sprocket assembly on ebay. This has a much better shaft for the sprocket, but this shaft has an anti-rotation roll pin fitted which fits into a machined slot in the aluminium housing. This seems like a very good idea to me, as on my old original the sprocket shaft (spindle) has clearly been rotating in the aluminium housings.
However, the newer replacement aluminium supporting plate (I have no idea what car this was from) does not have the semi-circular extension at the bottom with the extra bolt holes. Can anyone tell me if it is OK to use this part, and ignore the extra bolts at the base? Will this be OK with my original 140’s block? Engine number is G3736-8S.
Photo of the two together is below. Original '55 part is on the left, later one on the right.
That part appears to be from a 4.2 block.
Don’t you need the holes around the bottom end for the chain dampers?
Quite possibly Rob, the engine is away at the machine shop at present so it’s not easy to work out what goes where.
So, does the 4.2 not have chain dampers, just the 3.4? It sounds as though I can’t fit this 4.2 part to my 3.4. Is it OK to have the intermediate sprocket shaft turn in the aluminium mounting holes? Is there a way to stop it, or is this simply not necessary?
Having compared the fit, the 3.4 original shaft (that can turn) is a very easy fit in the aluminium support plate and can wobble a bit.
The 4.2 shaft, with the anti-rotation pin, needs drifting in to its support plate with a soft hammer, so is tight. But if I need the early one for the tensioners, I’ll have to live with the movement.
Just had a look on Martin Robey’s site, with a diagram of the 4.2. That apparently has spacers for the chain guides in place of the earlier full casting acting as spacer - would this setup work on the early car? I’m concerned that the spinning shaft will wear the holes in the aluminium supports, hence the change in design.
https://www.martinrobey.com/jaguar/e-type/e-type-series-1-4-2/engine/timing-gear/21625
Thoughts, anyone?
OK, I think I might be getting somewhere with this.
The chain damper fits inside the outer aluminium sprocket shaft support. On the early car, the dampers are a heavy casting with nylon faces. On the later cars, the damper is thick folded sheet with a rubber facing. As the metal on these is thinner, spacers are required to make up the thickness to the block.
These are the only dampers now available. If fitting to an early engine, small spacers are required between the damper and the extended lower part of the inner aluminium sprocket support. If fitting to a 4.2, longer spacers are required which go right to the block, as the lower extension to the inner aluminium casting, through which the bolts have to pass, is not present.
Therefore, I think it might be possible to fit the 4.2 inner cast aluminium support to the earlier 3.4 block, use the modern dampers (no choice - originals NLA) but with the 4.2 spacers, not the 3.4.
This would eliminate any possibility of the lower intermediate sprocket shaft rotating in the aluminium casings and wearing the soft holes bigger, which are not designed to be bearing surfaces.
Surely someone, somewhere, has tried to fit the 4.2 timing parts to a 3.4 at some time?
Thanks for your help, Rob, which pointed me in the right direction - but any further comments would be very welcome.
Looks like you are golden. The rearward end of the “new” intermediate shaft must have a Woodruff key provision to register with the square channel in the mounting plate, correct? Your thinking on the required damper spacers appears to be right on the mark, too…you must simply account for the thickness of the original plate which is no longer there when acquiring longer spacers, as you reasoned.
But ALWAYS “mock-up” (test fit) all the assemblies before moving on to final assembly as this will allow you to catch any problems before it is too late.
I think we’re getting there, Lee. The anti-rotation device is not a Woodruff key, it’s a roll pin that goes right through the spindle to locate soundly. I’ve measured the components so far and all seems to match up, the only real difference being that the rear retaining circlip groove on the spindle is in a different position as the 4.2 rear plate is slightly thinner.
I would assume Jaguar had problems with this spindle wearing the holes in the aluminium plates oval. Mine are certainly heading that way and the engine has done around 70k miles - never been apart before I stripped it, and all components standard sizes. There is a definite clunk as you try to move the gear up and down on the shaft, which doesn’t appear to be in the bush which is in reasonable shape. I think therefore I’ll go with the 4.2 pieces to improve on the original.
The roll pin approach will certainly do the job. Curious though, I didn’t notice the longer style damper spacers listed on the SNG site…meaning the longer-than-3.4L spacers you would need if you eliminate the bottom slice of bread in your bracket-thru-damper-to-engine block mounting sandwich.
On the Moss site, they show a different part number for those spacers for the 3.8 as opposed to the 4.2 parts…maybe the 4.2 E came with the shorter bracket, like the one you bought, requiring longer spacers?
Yes, Rob suggested this casting is from a 4.2. If you look at Robey’s website, the different part numbers are there.
I’m going with these parts because the intermediate sprocket shaft is available for the 4.2, but not for the 3.4, and mine is scored allowing sideways movement of the sprocket. As I said, it’s also slightly loose in the aluminium housing as it has obviously been rotating in it, which it’s not designed to do.
I’ve been following this with some interest and will also be interested in reading how it will work out for you after the install. Roger, do you have a part number for these later 4.2 brackets? Just so I can add it to my notebook on these cars.
Some random thoughts:
I’m surprised that none of the major suppliers are at least offering a rebuild kit for the old nylon-faced chain dampers. The rivets, nylon stock material and countersinks are available readily enough from, here in the states, McMaster-Carr and many others.
Turning of the intermediate gear shaft. My early '120: 670236 (don’t remember the engine number off-hand as I’m at work) has an oddity regarding this shaft I’ve never seen before when replacing the water pump. It has a horizontal flat milled on the top of the pin secured with a rectangular piece of steel about 1/2" in length and 1/8" height. Furthermore, it looked to be so well broached in there that I assumed it was (is?) original. I so wish I’d taken a picture as I’ve just now fitted the radiater and hoses.
There’s been a development… Crosthwaite and Gardiner make a new rear support plate for 3.4 and 3.8 engines, which have the full skirt at the base just like the original for our cars, but it is shaped differently to take the later design of intermediate sprocket shaft. It therefore has a slot for the anti-rotation pin.
I’ve got one coming to see if it will do what I want. They also make sprockets with bushes that have the original white metal bearing surfaces, rather than the bronze/brass usually sold. They build race engines for early Jags - C, D types etc. - and they’ve had some of the bronze/brass bushed sprockets seize on the shaft with potentially very expensive consequences. That’s why they started production of the white metal type. Apparently they don’t need reaming to fit their shafts. The prices for these parts are in the same ballpark as those of the main UK suppliers.
Wow…that sounds like quite a find…
Crosthwaite and Gardiner have quite a track record.
https://crosthwaiteandgardiner.com/our-history
They’re certainly no strangers to the XK engine - although when I mentioned the different shape of the 4.2 intermediate sprocket support, their technical guy said that they didn’t make parts for 4.2 engines, just 3.4 and 3.8s. A lot of genuine C- and D-types pass through their hands. That said, I suppose if you can scratch-build an Auto-Union C-type, you can probably build anything.
Sorry Christopher, I meant to respond to you on this.
The C&G timing gear support bracket looks like this:
You can clearly see the slot for the anti-rotation pin at 12 o’clock on the lower hole. As mentioned above, you need to use the later shaft with this - the original won’t fit. I can’t find anyone who makes the original style shaft for 3.4. And yes, Chris, they do make the cast chain guide, see p.1 of that parts list. Philip did say that they only fit those to wide-angle heads for racing - for everything else, they use the folded steel and rubber guides that JLR classic sell. The cast/nylon ones are much more expensive.
I’m nothing to do with them, by the way - I’ve known of them for years - they are huge in the British historic racing scene - but today was the first time I’d spoken to them.
These diagrams from Martin Robey show the difference in shape between the 3.4/3.8 rear bracket, shown in the first, and the 4.2 in the second image. Part 8 in both drawings.
The C&G bracket combines the design of the two.
The 4.2 lists part #15 with parts #16, either shims or thrust washers…did you get those as well?
I did order a couple of those too, but it seems odd that they are required for the 4.2 but not the 3.4. Presumably as the engine was developed, it was discovered that this one sprocket needed to be aligned more accurately than the others, don’t know. I don’t have any manuals for the 4.2 engine - does anyone know what the end float for the intermediate sprocket should be?
The used rear bracket I bought came with one shim. As there’s no shim shown on the 3.4 diagram, I’m inclined to leave it (them?) out.
Just spoken to Ollie Crosthwaite at C&G, and his advice is not to fit any shims. When they build up their engines they don’t use them - they assemble as per the original 3.4/3.8 engine, with no shims. Good enough for me - their engines are very expensive!
The timing parts arrived today, and look very good. The sprockets have the original style lead-indium shell bearing appearance to their bush surfaces, as opposed to the SNG Barratt ones which looked like scraped, or reamed, brass (possibly bronze, but very ‘copper’ in colour). The shafts etc. (I bought the intermediate shaft and the eccentric shaft) are beautifully machined, with larger lubrication drillings with a decent chamfer to the holes. My originals have no chamfers and are quite badly scored in places. As mentioned above, the sprocket bushes do not require further reaming but fit correctly as supplied. I also have one of C&G’s distributor drive bushes, which will need reaming to fit the new shaft once drifted into the block, but the block’s still away being machined. I’ll get the shop to fit and ream while they have it.