What is the consensus regarding value of an XK with an otherwise correct engine but it has no numbers stamped on either the block or head ?
It’s been buggered. Raises lots of questions.
That’s an impossibly broad and thus meaningless statement - as there are any number of variants of an XK engine, so ‘correct’ for what!
If you want to do your homework and identify each individual part - by Casting Number (if there) and/or Jaguar Part No - and can then relate that to a specific age/model of XK engine, and thus age/model of Jaguar it is ‘authentic’, and thus ‘correct’ for, then if that is a sought-after engine variant, it will be worth more, than just any unidentified XK engine variant, or indeed an unpopular/no demand XK engine variant. Then condition comes into the equation as well.
A good start would be the casting numbers of block, head, inlet-manifold, front-timing cover, water pump, carburetters, exhaust manifold - and is sump steel or alloy, flywheel type, and so on.
An unstamped head and block are likely to have been a dealer sourced replacement for a blown engine back in the day. I have an unstamped A-type C.6733 head myself.
The age and possibly the original destination car model can be determined by other clues as listed by Roger. Distributor model number is an easy identifier, though of course also easily swapped. Another useful number on the head can be found stamped either in the middle of the valley or at the rear.
This is what I wondered… What are your thoughts on how this might affect the current sale value of the car ?