XK6 3.8 Identification Help

I’ve got a long thread going for my 4.2 project, but I thought I’d start a short one for this since I don’t plan on doing anything with it for a while.

Turns out I had a cousin in rural West Virginia with an early 60s XK6 3.8 engine. Apparently in the 1980s, my grandfathers brother started a Jag sedan restoration. The engine was pulled and put in a barn. The car was sent to a local shop to have work done and the shop ended up burning down with the Jag inside. So, the engine stayed in the barn and now, 40 years on, it’s in my garage.

It might end up being total junk, I honestly don’t know. It’s probably seized as well. Can’t even tell if the head was painted or not. Couldn’t find a block number, only a date stamp. It has a two carb manifold and an automatic transmission. If anyone can help identify anything about this engine, I’d appreciate any knowledge you might pass along.

Seems to have a lack of freeze plugs like on the 4.2. Any chance this engine has all short studs?

Hi Doug,
I would guess that it is from a MK IX or a MK II. The engine numbers are on the oil pump mounts and on the front of the head (spark plug) valley.

The earlier XK engines like the 3.4L, 3.8L (like the one in your pictures) and the early 4.2L ones had the engine serial number stsmped on the right side of the block on the flat horizontal section just above the oil filter head. The first attached picture shows the area where the serial number is stamped on the freshly rebuilt 3.4L engine to my 1957 MK VIII.

The second attached picture shows where the serial number is stamped on the front of the cylinder head in the earlier cars as well.


It has the original York AC compressor and pulley. I therefore doubt the Mk9 legacy.

It’s not MK7 8 or 9. Or XK series. Wrong oil filter, electric oil pressure, sender, lifting hooks on head, different breather cover with the outlet pointing to the left not the right. Not 420 as it’s a 3.8.
Therefore must be MK2 or S type. The 1961 stamp, if that’s s date stamp, it’s a MK2.
Check out the air cleaner bracket on the head, they were different. I think that’s a MK2 one. That’s the key!
Funnily it has a pre engaged starter like the 240/340 420 series.
It will definitely be a short stud motor.
My money says it’s a 1962 MK2.

I have a 1963 Mk2 and this engine has all the Mk2 hallmarks including: sump, dipstick, engine fan and the correct mounting for the air cleaner. The cylinder head would be painted mid/dark blue. The transmision looks like a DG250 - also correct for a Mk2 of that vintage. Paul.

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Assuming you plan to sell it some day, the buyer will want to know those stamped serial numbers on the block and head. A 3.8 Mark 2 will normally begin with the letters LA, LB, LC, LD or LE.

Thank you all. Did find the block number. LB 7555-8

Don’t know if I’ll sell it. I figured I’d revisit it in a year. The 4.2 I rebuilt will go in the Jag replica that I will build later this summer. A 3.8 certainly would be a bit more authentic for that, so I’ll ponder that option at a later date.

Is the cylinder head on this 3.8 aluminum or iron? So much crud on it, I can’t tell.

All XK type heads are aluminum. All blocks are iron. Production date for that number is mid to late 1962.

Whatever you decide to do I would start spraying penetrating oil over the studs and bolts.

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See if the heads nuts will undo, if so remove all and the washers ( if you can) get penetration fluid down the sides of the studs where they fit through the head. Let it stew for as long as you can. ATF is quite good for long term soaking as it doesn’t evaporate. A lot of penetrating fluids do just means you do it regularly. Nice find! Good luck.

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Thanks. I’m assuming you mean automatic transmission fluid when you said ATF? Any particular type or brand work better than others?

It’ll be a year at least before anything is done, but I’ll start ‘marinating’ it now.

Indeed: ATF is auto trans fluid. Mixed with acetone, its a top penetrant.

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Best penetrating out there, Home Brew ATF + acetone. 50/50 mix.

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