In my quest to find my half speed tap/knock it seems to be from No 6 or 5 Exhaust side, valve clearances are correct the buckets are in good shape and after taking off the exhaust manifold the guides appear to be in the correct position as are the tappet guides. So next off with it's head can it be removed with out removing the heater box? to me it looks like you should. The car is a right hand drive 3.4 Mk2 1963 and the heater box is on the left hand side.

 

Anything is possible but it is easier with the heater box out of the way. You will be removing all the hoses to the heater anyway then I think there are only five or six 7/16 bolts to remove with the heater cable and the box is out of the way. It is a bit like saying can the head be removed with the bonnet left in place. Yes but it is a lot easier if you remove it.

 

I removed my head in my small attached garage and just disconnected the hoses but the box stayed. I never felt it was in the way.

 

Are you sure that the tappet/bucket guides are all tied down properly? Half speed should be Cam, Valvegear related. Cam speed half crank speed.

Unless you have a loose valve seat.

 

 

You can do it without removing the heater entirely but it needs to be unbolted and moved over enough to get the head off.

My best advice for doing a head in the car is use an engine hoist to lift it off (once its free) and put it back on as doing it any other way on your own is a real struggle. Sadly when I did mine I didn't have a crane or any assistance so had to do it on my own which was challenging.

Have you checked the compression on the engine? Did it just start making the noise or has it always done it? Its possible that a valve might be slightly bent and a previous owner has shimmed it up either deliberatly or without realising to quieten it a bit.

I have to say that other than a bent valve there isn't anything I can think of that would cause a noise which might be solved by taking the head off.

Have you checked the top chain tension? If possible put an endoscope down to check the chain guides.