Morris Minor Owners Club

I have no experince of engines, I can do timing and change spark plugs and adjust tappets and the like but the inner workings are a mystery, but my engine is not healthy, it clatters a lot and a friend did a compressions test and it showed different compression in each cylinder and the oil light comes on when it is very hot and stuff - so where would a beginner even start!?

Is there for example a book or something on how easily to rebuild an engine like this written for idiots?

Yes - it's called the Workshop Manual! If you don't have one - PM me...........
And yes - the Minor engine is simplicity itself - nothing difficult. I'm sure plenty of You Tube footage too! But I would suggest getting a spare engine - and either stick it in your car temporarily (if it's better than yours) or rebuild it, and the swap them over. This way there is no pressure to rush anything.

Your trouble will be, not having experience of engines, that you may not be able to tell which parts are worn and need attention when you do dismantle it. Your cheapest bet would be to source a half decent engine to get you back on the road, then, if you really want to, use your old engine to learn on without any timescale pressures. We all started somewhere.
Don't think you will save a fortune doing it yourself, especially if you have to buy a heap of special tools like spring compressors, piston ring clamps, torque wrench etc. Do it to learn or because you want the satisfaction of rebuilding yourself, not to save money. You know there is always someone who will help on here so don't be afraid to ask if you decide to rebuild.

When was it last serviced and was 20/50 oil used?
The clattering may easily be a worn timing chain.
Taking the head off and sorting out the gasket and/or valves would be good practice for a bigger overhaul and give you a good idea of the state of the bores.