Wrong timing or Big end bearing gone?!

Does it get worse or better as the engine warms up? Big ends and most bearings get worse warm, piston slap which can be quite noisy gets better. Gentle acceleration usually quietens big ends. Pinking due to advanced timing or hot spots (burnt valve/lots of carbon) that's bad enough to knock heavily sounds rather like a hammer on an anvil and will be worse when hot and heavily loading the engine (like your hill climb did).

IME, the big ends rattle at low revs, and stop at high revs, because of the extra cushion of oil.

ISTR that knocking at high revs is little ends.

Pete.

It doesn't burn oil, no overheating, start staight away when cold & hot. Basiclly, It doesn't have any sign shown the bearing gone apart from that noise.

Thanks for reply

Any idea?

Probably something else entirely then, pop down the garage, but unless you've been driving it with no oil it's probably going to be something much cheaper, like an engine mount.