A different challenge...Not an Xm...but of course, a non-runner.

[Dieselman]

Thanks. I fully understand this was my error, but have noticed a mix of metric and UNC on both engines, (iirc, 1985 and 1989). I didn't expect Jaguar to have gone from British Standard, to American Standard, before switching to Metric.
The Uk went Metric for engineering applications in 1965.

I find it hard to believe Jaguar couldn't afford a few new Metric threading tools. They must have been replacing tooling on a regular basis, just pick a change over date and go for it.
I guess Jaguar were just being stubborn, which unfortunately typified the British car industry and in particular British Leyland.

[xantia_v6]

Now that I think of it, the crankshaft pulley bolt is 7/8 BSF, a hold over from the pre-war design/tooling which was bought from Standard when they ceased production of 6 cylinder engines.

Jaguar always struggled to get any tooling expenditure approved by BL. The 1992 facelift of the XJS was designed in about 1980 iirc but only tooled up after Ford took over. The 5 speed manual transmission for the XJS was designed and 20 prototypes made in about 1973 but the tooling was never approved for production.

[xantia_v6]

This is my 1975 XJ-S, which is 98% original, but rather tatty. It is still running Lucas OPUS ignition and Bosch/Lucas d-jetronic injection. D-jetronic was technically obsolete before the XJ-S was launched, but no replacement had been developed for 12 cylinder engines.

IMG_20260214_190021.jpg

IMG_20260214_185951.jpg

IMG_20260214_185924.jpg

[Dieselman]

Thanks for the crankshaft bolt info, it makes me feel slightly better...

I do like the first series Xjs.

[Dieselman]

I have drilled and Heli-coiled all the threads for the sandwich plate to fit to the crank-case, apart from the one where the bolt broke inside the thread and with a central point, meaning it was difficult to make a centre punch mark for a drill to accurately drill down.
I used a small burr to flatten that bolt, which caused a little damage to the aluminium, so as I was at a neighbours I asked him for a bit of 12mm aluminium bar, which I made into an aluminium insert for that thread.

WP_20260211_006.jpg

WP_20260217_003.jpg

If I had the engine support beam in advance I would have dropped the subframe at the start and could have probably removed all the bolts with some heat, but with the subframe in, access was impossible.

I had noticed the Alternator trigger wire was disconnected, so while I still had good access I tested it was indeed the Ign feed, then connected it. I tested it to both Gnd and the alternator contact, which should be Gnd until the Alt starts charging, at which point it goes open circuit, putting the charge lamp out. The charge lamp doesn't currently illuminate...

Note just how good access is with the subframe removed...

WP_20260217_006.jpg

WP_20260217_009.jpg

WP_20260217_012.jpg

The exhaust is a very tight fit by the subframe mounts, especially on the left side. On checking the manifold to downpipe nuts I found they were finger tight only, so loosened the downpipe to exhaust pipe clamp and tightened the manifold nuts, hoping to gain additional clearance. This hasn't really been successful, even though the engine mounts appear in good condition. I suspect the downpipe is a replacement part.

WP_20260217_015.jpg

WP_20260217_016.jpg

I scraped the old gasket paper off the oil pump ports, lightly sanded and degreased before fitting new gaskets with a smear of Hylomar blue, installed new O rings, slid the pipes into the elbows, then installed each elbow, suction/output pipe as a unit.

WP_20260218_002.jpg

I changed the original suction pipe which was designed for the relief flow oil cooler system for the one designed for the full flow oil cooler. The size difference is noticeable: the relief flow pipe o/d is approx. 7/8", the full flow one is approx. 1 3/8".

You don't see this in the pic, because the smaller one is closer. I had fully rebuilt the sandwich plate before taking the picture.

WP_20260218_005.jpg

I fitted the sump baffle, remembering to apply gasket sealant to all the side bolts, as these are open threads which lead from inside the sump to outside the crank-case. These are known to wick oil up the threads, causing leaks, if sealant isn't applied.

WP_20260218_007.jpg

WP_20260218_008.jpg

WP_20260218_010.jpg

After installing the sump, new rubber hose onto the pressure relief return, new O ring and bolt down the filter housing/return unit, I filled with oil and with the filter not installed, cranked the engine.

Never has a large oil leak been such a welcoming sight...

WP_20260219_001.jpg

Filter on and start the engine. The oil pressure isn't particularly high, but this engine is currently filled with 5W-30 oil and rapid flow, coupled with the oil reaching it's operating temperature, is more important than high pressure, as plain bearings and sliding surfaces create their own oil wedge when moving.

WP_20260219_002.jpg

WP_20260219_003.jpg

Talking of oil, I noticed that simply using the fresh oil and a paper towel was sufficient to remove significant quantities of the baked on carbon from the engine components; oil and small brush for the breather flame trap.

Subframe re-installed along with damper top mounts, Abs sensors, front brakes re-connected and gravity bled. I forgot the Arb links, so had to do those later, with the wheels fitted, which was a bit fiddley, but possible.

WP_20260219_006.jpg

WP_20260219_007.jpg

Using a smear of copper-slip really helped with installation and should prevent any further seizing of fastenings. If you want a fastening/part to move either now, or later...grease it.

As the Magneti Marelli ignition system uses a coolant temperature mounted into the R/h water rail I either had to swap that, or drill the casting. I opted to swap the rail so removed the R/h air filter housing and disconnected the electrical connections, etc.
I intended to swap the complete rail, but the very rear-most bolt, under the wiring loom and vacuum pipes, wasn't coming out, so rather than risk a broken bolt I fitted only the front casting and metal pipe.

WP_20260220_002.jpg

WP_20260220_003.jpg

WP_20260220_004.jpg

WP_20260220_006.jpg

WP_20260220_008.jpg

New gaskets and 82°C thermostats both sides were installed. Remember to position the jiggle pin uppermost for air bleeding.

[xantia_v6]

All good progress.

I think that at the build date of your car, the exhaust down pipes were made from mild steel, so the stainless examples you have would be replacements. They are always a tight fit against something.