Replacement Engine for a "lumped" XK140

A new member and owner of an xk 140 FHC. Unfortunately it has a Chevy V8 and auto transmission in it currently. I’m going back to Jaguar…and looking for some advice. The heritage certificate shows it was an SE, not “C” type heads, and BW auto transmission originally. I got it at a good price, have a decent budget to spend, body seems ok, interior and paint that I can live with. I really don’t want to end up with more in the car than it’s worth. My goal is a “driver” rather than a prize winner.

I’ve been doing some engine research and it seems like I have three options: 1) find a matching G series engine and box so I am as close to “matching numbers” as possible and rebuild them, 2) find a period 3.4 engine from a Mk1 or mk7, (maybe even an runner?) and appropriate 140 box/5 speed, or 3) go big and drop a 3.8 in it and appropriate 140 box/5 speed.

Which would you chose - 1, 2, or 3? It will never be a matching numbers car, so worth going for a “G”?

If I go for a non-G engine…Oil Sumps, pumps and filters seem to be the problem from posts here and conversations. 140/150 sumps are scarce as everyone knew but me, and no economic reason to sell it separately from an engine any more. Mix and match on the sumps and you may need a new oil pump/piping as well. So… which engines would “drop right in” to a 140 as I don’t have the parts to move across to adapt it? If not drop right in, can you modify other sumps to fit… e.g. if I went with a MK1 engine (which has the right style oil filter and mechanical tach) I’ve been told you can cut off the sump “wing” on the exhaust side, close the resulting hole, and the exhausts will fit.

I recognise a question AND a follow up are pretty cheeky for a first post but hoping to learn from other’s battle scars.

Big shout out to Rob Caveney in Hawaii who helped me get an honest view of what I was buying. Suspect he will be reading this - he’s posted in the past. Quite a gentleman.


How do you intend to use the car? Casual classic car cruising? Major excursions far from home? Sporting use such as auto crossing and an occasional track day? Car shows?

It could be if you find a number stamp maker : >)

If it were mine, I’d have some fun driving it until I found a suitable engine for it. Since you are not interested in show, I’d look for a local runner engine, either 3.4 or 3.8, and do the swap when you have everything you need - modify the pan if you have to. You can do the correct engine later if you find it, then sell the runner.

However, if you have to start from scratch with building an engine, it would be about the same rebuilding cost to do the correct one if you can find a reasonable core. Then it would make sense to me to keep it a lump until you find the right core.

The ethics of re-numbering engines is debatable - most buyers would be upset if they found out after the sale that their “matching numbers” car was faked. Even with disclosure, you don’t know what will happen after the car leaves your hands. I’m not sure about the legality, either. I’d do some careful research before exercising that option.

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The operative word being " ÏF "
While it may be somehow comforting to think a car is ‘matching numbers’ the reality may be different. We had an old mechanic from the local dealer give a talk at the Register one night.
If you think back to the 40s-50s, these cars were just transport to the owners. If an engine needed a rebuild, they didn’t want to wait weeks without their car. So the dealer had an extra engine number milled off the block . When a car came in needing an engine rebuild, this spare had the cars eng number stamped on it and went into the car and the owner was pleased it had all only ,rebuilt and kept waiting for the next round.
Not strictly legal I suppose, but Jaguar used to supply spare engine blocks with no numbers stamped. I have seen SS and XK blocks like this.

Frankly an owner is exactly as happy thinking he has the original block,as if he really had it. And often it seems that ‘matching numbers’ has replaced any serious attempt at originality.

John - most times it won’t be more than 100 miles from home, but I will definitely take it on some excursions into Europe … maybe annually. So reliability will be important. I think I’ve already made my mind up that I’ll upgrade to a high torque starter, electronic ignition, alternator.

That’s a nice distinction… if it’s a rebuild go for a correct “G” series, if I can find a reliable runner drop that in straight. Still leaves me with problem with the transmission. There’s a MKII runner that I could get at a decent price, but I don’t think the moss box from a MKII sedan can be modified to fit. Or can it?

I’ve read several threads about the merits/legitimacy of the matching numbers debate … and maybe an issue I’ll think about if I get that far down the line. Seems like that’s one for a few beers down the pub!

Which just proves the point, that all this hullaballoo about matching numbers is just a mind f**k.

Far as I know, if you get the proper trans cocer, it should work. I also will admit to not remembering much about which gearboxes XKs used…:crazy_face:

We share a similar story, In my case a XK120 with no engine.

You can put the correct 140 Intake manifold on any 3.4L or 3.8L that does not have a straight port head.

I wouldn’t rule out an early 4.2L engine, which has the aforementioned straight port head. There are a couple of ways to put two carburetors on a 4.2 head. One using the early saloon manifolds (works, but not good aesthetics) and another using the twin Stromberg manifold off of a Series 2 E-Type stripped of all of the emissions gear and redrilled to accept two manual choke 2" SU H8 or HD8 carburetors.

E-Type sumps fit the XK chassis better than the XJ6 or other saloon variant. Avoid XK120 sumps, they are very pretty, but they will only work properly with the very early 3.4L block and oil pump.

The early 4.2L oil filter mount fits the chassis and has the benefit of using disposable spin on canister filters. It will also accept the big Porsche 911 Turbo oil filter.

You can buy a complete conversion kit from several sources to put a Borg-Warner-Tremec T-5 5-speed gearbox in the car. T-5’s can be bought new or scrounged from a 1990’s Ford Mustang GT.

This is the engine I built up from the parts list above using the 3.4L shortblock from a1965 Mk2 and the straight port cylinder head from a 420.

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Excellent adaptation, and no one will be the wiser!

I have never quite grokked all the hand-wringing about the “correct” engine angst.

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I like your air filter!

In your initial posting, you mentioned 5 speed. Since you could use this if you find the “correct” engine, why not just do it at the beginning? I don’t know 140s, but I think you could make other transmissions work, but then you have to modify again later for the 5 speed. It’s off the shelf new, and pretty much bolts up. I wouldn’t do it, but original moss boxes are not hard to find - I have some extras for 120 and marks if you really want that and are close. FWIW, I also have a extra short block and pan for a 120. Not what I recommend for you.

I agree that 4.2s could also work. I think the mods you mentioned are good. I like an electric cooling fan, and an alternator is pretty necessary for that. You don’t need a high output one, but do consider modifying the ammeter to a voltmeter to avoid fire hazard. I have electronic spark conversions on my several British cars and they work well - carry your old points and condenser for the chance of breakdown, but I’ve never needed them. I haven’t had the need to modify my starters, but a lot of folks do. What bellhousing you use will dictate your flywheel and starter choices. I modified my xk 120 with an xj6 spin-on filter assembly, with the extra benefit of the oil cooler - easy mod except for figuring where to mount the cooler. There are lots of things you can do to make the xk cars more modern, but they are simple and pretty solid as is.

WIX 46016 for a 1980-89 Subaru. Same as yours?

The Denso alternator in the photo is 45 amps, originally for a Kubota diesel tractor.

The early XJ6 filter mount did not have the cooler lines, so it is simpler to install, but uses the same spin-on filter.

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I vote for option #2 then #3.
XK140/120 engines are completely interchangeable as a core motor. No need to change sumps, pumps etc. But you have to stick with the correct ancillaries if you don’t want to fiddle about a bit. The only change I’m aware of (excluding the early xk120’s) is you will need a slightly modified off-side front engine mounting bracket. I had one made by a local shop for under $50 (I supplied a 120 bracket and they made it into a 140 bracket, but you can go the other way just as easily).

Very nice work. I agree, the early spin on is easier, but I like my cooler. Question - looks like you plumbed the return into the sump drain. Why there instead of the side port?

I like to just get a gm 1 wire alternator. You can use the 4 rectangular mounting points on the water pump with a spacer block, and an off the shelf brace, but it does mount higher. Like you, I change to the smaller belt/pulley and use a later damper. Looks like you have an early car from the front mount.

Yes, early XK120, 1952 dispatch, with the horseshoe front mount.

First, this is a S1 E-Type sump, something nearly as old as an XK, and I was concerned with the integrity of the threads in the aluminum sump. The epiphany came when I realized that both the sump drain and the discharge port on the filter mount were both SAE straight thread, so I could easily fit AN-8 x SAE adapters to both, making for an easily removed hose with AN swivels on both ends. This makes draining the sump very easy and the wear point is in the steel adapter or hose swivel, not the aluminum sump. Second, the discharge line from the filter mount points that direction, so the routing complied with what I considered to be good engineering practice. The photo above was taken early on when the engine was still on and engine stand, the photo below is more recent and shows engine in the chassis with the earlier filter mount without the oil cooler hoses.

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That’s the same filter!