Dear All,
I'm considering the installation of a recently reconditioned XJ6 4.2 engine into my Mk VII (low compression - rings).

As engines evolve with time, what is different, enginewise, that must be swapped to do this installation?

Any advice appreciated.

Regards,

Tony

 

Tony, maaaaate, you are taking me back to the '60's, so this is going to be very messy.

The MK7 was 3.4, used for ages after that year model.

The 4.2 XJ engine will be "slightly" longer, no idea how much.

The MK7 engine mounts were directly behind the timing cover face on the side of the block, the XJ are about midway (give or take) down the side of the block, soooo, the holes for the MK7 engine mount brackets may well be in the XJ block, and used for power steer bracket (RH side), and alt/air con bracket (LH side), ???????.

The trans should be fine, just watch the hole in crankshaft for the spigot. a spacer sleeve may be needed.

Engine height should not be an issue.

Exhaust probably OK, but not rocket science to rework.

Radiator integrity will be paramount, as extra HP = extra heat to disperse.

The tacho drive will need some imagination, MK7 is cable (now the memory is real fuzzy), or is it pulse generator on the inlet camshaft??, dunno, and the XJ engines were all electronic pulse from the coil etc, so no drive facility in the camshaft end.

That is all I can think of at the moment, but sure as hell there will be hundreds of little niggly things that will need sorting.

 

I don't think the 4.2 engine is longer. When the 4.2 was developed, the existing 3.4 and 3.8 engines were still in production, (also the 2.4 short block engine), so the 4.2 was designed within the existing block dimensions and the bores were siamesed in two sets of three, (1-2, 2-3, and 4-5, 5-6) to get the wider bores in , the stroke remaining the same at 106 mm. The head was left unchanged, so the combustion chambers are not an exact fit onto the bores, but it works regardless of this.

I may be wrong on this, but I am pretty sure I'm right. What may have changed is the block casting in terms of the engine mountings, but only a look will determine whether this is so or not. You probably also need to check the oil filter position as I think the Mk VII is different. However, you can probably fit the assembly off your old engine, but will probably need the sump as well.

Actually, the original 3.4 engine of 1948 was probably the best of the lot. The 3.8 was OK, but needed liners for some reason. The 4.2 was a bit of a cobble to be honest, and the later ones, with the long stud block were notorious for cracking between the bores. 7 out of 10 7L blocks and 8 out of 10 8L blocks crack according to Brian Reid who was rebuilding them regularly in Hinckley in the 80s and 90s; he may still be doing so. He sold me an uncracked 7L block for my Series 3 engine.

Cure for the cracking involves lipped, (or 'tophat') liners. Later blocks from about 1982 didn't crack because the water passage ways on the siamesed bores were cut from the top instead of via the bores hence has no liners.

What is your engine number ? If its a 7L or 8L blocked engine you need to check for this cracking, seen only when the head is off. Which XJ did it come out of ? Series 1, 2 or 3 ? I think Series 1 engines were OK.

 

Hey Grant,
Thanks for the info and you sure don't look your.....age!!

I'm in Melbourne and am thinking of joining the club but I find with car clubs is that the people there only talk about cars.

Fraser, thanks as well. I'm glad that there are people out there who know these sorts of details.

The engine sold before I could understand the differences.

It was a fully rebuilt engine with receipts for $7000 that sold for $383 Aussie dollars (about US 350).

Oh well, I'll keep looking.

Thanks again,

Tony