In a cold engine the liner is held tight by metal contraction. As the motor heats up the aluminum block expands more than the steel liner, and at some temp the liner comes loose. That is when the rap starts. That's why it has a sudden onset, and that sets it apart from gradually increasing piston noise.
|The original Land Rover V8 liner, the one that breaks loose and moves (c) JE Robison Service|
|A flanged liner, which cannot move (C) JE Robison Service|
|Land Rover block, ready to fit flanged or top hat liner (c) JE Robison Service|
The change to flange liners addresses a fundamental weakness in the engine, and renders them much less susceptible to future failure. To read more about liner issues and what we do to rebuild and improve these motors I suggest this essay from 2012
This article applies to all pushrod Land Rover V8 engines, including the motors in Range Rover Classic, County LWB, Discovery, and Discovery II. It is not applicable to the newer L322 Range Rover, or the Range Rover Sport, LR2, LR3, or LR4.
Thanks to master technicians Paul Ferreira and Danny Ferrari for finding and figuring out these failures.
John Elder Robison