Hi. I'm new to this forum so I'm making my first post a headlong dive into (potentially) major engine repair.

I recently purchased an 85 XJS HE (which my wife instantly claimed as her car). It has a faint ticking sound in the drivers' side head. The previous owner had it diagnosed by a mechanic as being a broken valve spring. I haven't disassembled the top end to confirm this as yet. Sounds like it anyway. From what I understand it has a dual spring and, if one failed, the tappet would loft the valve with each revolution of the cam. There isn't any grotesque hammering that says the valve has dropped into the cylinder.

I admit I'm not familiar with Jaguar repairs but the quote that the previous owner had was for a complete head removal in order to repair the problem.

Is it possible to replace a broken spring without removing the head??

I've done similar repairs on my other cars without resorting to a complete removal of the cylinder head. The procedure I've used is as follows.

1) locate cylinder to be repaired on compression stroke.
2) remove spark plug and insert a few feet of rope into cylinder.
3) manually rotate engine to compress rope between piston and valves
4) Remove cam
5) Compress spring and remove keepers
6) replace parts and re-assemble

Does anyone have any experience they could share??

My other question is regarding cylinder head identification. I located another set of V-12 heads but the gentleman isn't aware of the year/model of car that they came from. Are there any casting numbers or other identifying features that differentiate cylinder heads used in particular years? Are there any parts that I should avoid like the plague??

Any assistance would be greatly appreciated.

David