so, I'm finally towing Alfred home from the parking garage he's been residing in since he failed to proceed one day last year.

Pulling the plugs revealed a odd looking cylinder 3 top. Magnetic probe fished this off it.


This it a bit of a valve. The top side to camera, a bit of the seat is visible on the opposite side.

Piston appears to be undamaged from my limited view. He ran fine the day this occurred. Parked him and when I tried to start him at lunch it made a bad sound then would not turn over at all.

Piston 3 is up, and I assume is either binding on the stuck open valve or wedging the broken off partial valve against the head.

so, how do I proceed?

 

Absolutely no other option, off with his head (s)
Do not try and turn the engine, you may drag broken bits down the bore and score it.
You can set the timing again afterwards if you decide to proceed with the repairs.
You may be very lucky and only have a dinked piston crown and minor damage to the combustion chamber face, or you may have a catastrophic crack in the piston.
Either way, the heads are coming off.
If it were mine, (as I'm doing at the moment to my 4.0L V8 due to a blown head gasket), complete top end gasket set and all new valves (in your case) are the minimum. It doesn't mean that any of the other valves will fail like that one, but better safe than sorry.
If you can do the work yourself, great, just the cost of the gaskets, valves and any other things that might need changing in the process; if it's going to the garage, look at a four figure sum for repairs.

 

Oh I'll be doing this myself! My Jags are unaware that there are professional repairmen. I want to keep it that way. Or, rather, I am going to keep it that way.

This is will be my first head pull oin a jag. I hope the head in the 6s are easy. The v12s appear to require a threaded slab of steel to pry them loose.

Assuming ( praying ) there's not piston damage, can I forgo any head or block face machining and pull this all off at home?

Any recommendations on parts source for the valves and gaskets?

 

Treat it as any other head removal you have done, minus setting the timing first.
There's wiring and brackets and all manner of stuff that will P*%$ you off no end at first, but patience is a virtue.
As a general rule I have the heads skimmed and pressure tested when I have them off, just to be sure they are good. The block face I clean up with a window paint scraper and thinners.
As for parts in your part of the world, I have no idea, but there are links on the site thay say they do good deals for forum members. I haven't tried them personally.
My full headset cost me £140, and valves are around £10 each over here, but that's trade prices, not retail.
There is lots of info on the site about what to look for when you do jobs like these, like the condition of the water pump impeller, the plastic ones can tear and break up, deteriation of the throttle hoses and stuff like that. All useful stuff.
What you decide to spend on it depends on how much you love it really.

But the first point of call before you buy anything is to have it apart and asses the damage, then go from there.

 

From my point of view and past experience with a similar "mess' in a somewhat similar yet different critter, the cylinder head will be a mess.


Fixable, in theory, possibly. $'s in today's world, many.


I got mine welded up and reground and a seat inserted. Back then, not all that bad. were I to do it again, I'd find a better undamaged head.


That valve debris is much harder the alloy used in the head casting...
A few bangs and deep gouges take place...


Carl