I've got a project for which I'm going to need a 4.2 XK6. I want to pick up a core that has the best engineering, and usually that means the last few years of production. Does anyone here know which years I should be looking at to get the most "tweaked" engine?

Also, does anyone know the engine (or head) length of the 4.2 XK6?

Thanks,
Untame

PS -- I only really care about the long block. Not the computer, fuel delivery, accessories, etc.

 

An engine from 1983-on will definitely have the slotted, (for water passages), block giving more integrity to the block and thus preventing the notorious cracking between the bores suffered by cars up to this point.

Alternatively think of an AJ6 engine, which is all-aluminium and better, or even an AJ16, even better. These engines are around the same length as the XK, and at 3.6 or 4 litre capacity.

 

Thanks, Fraser. For our cars style is as important (more?) than performance, so the XK6 has a classic look we want.

Those 4.2 siamesed cylinders... are they grouped into pairs or two groups of three? Are there mains between each cylinder?

One more thing... are the 3.8 cylinders spaced evenly?

 

The siamesed cylinders on the 4.2 are in two groups of three. I cannot remember what the earlier 3.4 and 3.8 engines had. The crank has seven main bearings, one between each crank throw.

Cracking of the block casting occurs between 1-2, 2-3, and 4-5, 5-6, (not necessarily all of these), due to the presence of machined coolant passages about 1" below the block deck thus forming narrow bridges of metal between the bores above the slots. The machined slots are closed off by steel liners about 1/16" thick; these don't crack. Once cracked, the metal bridge sinks slightly thus taking the pressure off the head gasket. Continual HGF is the result, (as happened to me). Cure is to machine out the liners, machine a groove on the deck round each bore and fit lipped liners to cover the cracks.

Or use a later engine which has vertical slots for coolant passages between the bores and no liners.

All the above applies to the long stud engines. There was a short stud engine before that and I'm not sure if the problem occurs on these.