Very Strange Head Casting!

Gotta a puzzle for those smarter than I!

I just picked up @Craig_Balzer’s spare motor, and noticed some seemingly fresh machining marks, but upon a closer inspection, the entire head casting is not like anything I’ve ever seen.

Checkout the mating surface and front shelf differences between the head and a standard head.

In addition, the spark plug holes are drilled completely different than the way the factory did it.

Supposedly off of an early ‘84 XJS, but I have probably 10 V12’s in inventory, and I ain’t seen nothing like these.

Thoughts?? Factory EAC and pinwheel stampings, for reference.

Any stampings on the back side of the heads?

There were some strange one offs made for TWR and G44, but in production? IDK… Usually other markings are stamped in the heads (on the rear -often or at the rear of the V if head are with the original - special - engine.)

~Paul K

Given that there were thousands of heads produced, there was more than one mold, so there will be variations out there. The relevant parts aren’t where a different block of wax was used as an insert but whether there are holes or passages or machining in different places.

The only relevant detail in these pictures is that three slightly shorter studs can be used to bolt up the timing cover on the upper pictured head vis-vis the the lower one.

kind regards

Rear markings as pictured:

Also note the machined finish on the intake ports, it’s definitely different than usual, and the spark plug holes, while in the HE locations, have completely different boring marks. It really looks (from a distance) as if a massive amount of repairs were done via a build up of material and then remachined, until you get at eye level, where the casting is absolutely as one.

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This post would have duplicated Jeff’s info

it could be that Jeff used the “back” button of his browser, and this created the same content twice