We had 40+ 6LXB’s and LXC’s at our quarry and I was rebuilding approximately one a week for a while. They were fine when trucks were running around at 40 mph and grossing 24 tons but they struggled above that. Ours were all 30 ton eight leggers, mostly Foden with a few Sed Ak 400’s, and they always seemed to overheat on either number 1 or number 6 cylinders resulting in piston seizure or in a few cases the gudgeon pin coming out though the side of the block. Some chucked a con rod out as well, resulting in a new crankcase and block required. When they got worn after a few of years oil consumption would be around a gallon per day and then we usually fitted an exchange block and pistons. Valves hitting pistons was another thing, usually when the camshaft sprocket bolt came loose due to the tab washer breaking, the LXC’s had to have LXB type heads put on them under warranty when new as they drank oil otherwise. I took a couple of LXC powered Fodens back to Patricroft as they just would not pull properly, Gardner’s answer to me was that if you wanted something to pull better then you should have ordered a ■■■■■■■■■ 
I also took one back with a water leak from a plug in a new cylinder block that I fitted, there was a ‘special tool’ to tighten the plug, but the foreman had gone on holiday with the key to the tool cupboard so they couldnt do it, eventually it sealed itself with rust. Couldn’t make it up could you?
I will say that we never had crank problems though, and the engineering quality was second to none but the Rolls 265’s that replaced them were far more reliable in service, mine did ten years and God knows how many miles without even having an injector replaced.
For all that they are still my favourite engine and I wouldnt mind rebuilding another one, though that would seem unlikely now!
Pete.