Notorious in the trade for oil faults,

basically a lack of oil/filter changes.

Resulting in worn/stretched timing chain/tensioner but also oil starvation to the crankshaft.

Which from the sound of it is your problem,

Big end knock from a worn out bearing.

usually means engine is scrap metal.

Sounds like you have two issues and I hope I'm proved wrong.

The main issue with these engine is the cam chain/tensioner wearing - you hear lods of them rattling away. - this would need sorting before it gives way/jumps and the rattling chain can release little bits of metal into the oil which could eventually damage other parts of the engine - I think this possibly has happened here.

As the big end bearings (and possibly main bearings) start to wear badly (oil contamination as above, overheating, thrashing, lack of oil changes) then oil pressure will be lost with oil leaking and dropping back to the sump and eventually a knocking noise appears especially when the oil is thinner (aka warm) and extra engine load displaces the oil giving near metal to metal contact (knocking). This then creates overheating of the bearings and more rapid wear.

Sadly I've experienced big end failure twice in my motoring career when young and skint! Once was with a 2.0 Ford Capri which was suffering gradual cam shaft failure due to a common oil spray bar issue (probably not helped by infrequent servicing - I've learnt since!) - eventually a big end bearing (possibly more than one) went big time. Another time was when a Datsun100A badly overheated (blocked rad & v hot day) which cream crackered the oil. Same symptoms as you - just about OK when cold and on the flat driving gently but when warmed up under load - what a noise.

How about finding a second hand engine to fit as a replacement?

Edited by Big John on 28/10/2018 at 22:17

Can understand the noise increasing when climbing, but why on cornering - unless CV joints or drive shafts are wearing too?