I had a 1600 x flow OHC late mark 1, 1974 - what a complete bag of poo! Its the only car I have bought from new, and the last ford I will ever own.
A design fault meant that the oil feed to the overhead cams failed. So after a spell it started 'clacking'. Knackered camshaft, followers and collets.
Ford in their infinate wisdom designed an overhead camshaft that could not be lifted out vertically - it had to be withdrawn longditudinally through the (dry, worn, noisy, oil starved) bearings. Fine. Except some less than moronic cretin designed it so that it only withdrew to the rear of the block, thus fouling the bodyshell bulkhead.
So you need to remove the whole head assembly, thus disrupting the timing, and requiring 3 special tools to do it.
I actually got quite good at changing the cam, followers, oil feed pipe and resetting all the timing. ford ( lack of capital is deliberate ) did it 5 times under warranty - I did it 7 times myself. I could do it in about 2 hours - ford's fastest response was 2 weeks.
The early 3.0 V6 ones were the devil to control, but luckily the engine mountings corroded and stopped them going anywhere before most owners were killed. I think the later laser 2.8i ones were better - but since the bottom has rusted out of pretty much all of them now, anything that passes an MOT should be snapped up.
Why not look out for a cheap but good Jag XJS? I did