V8 lifter noise?

Thanks for the replies, I neglected to mention the cam is a PC216 supplied by Triumph Rover Spares in South Aust as were the lifters.
Found my stethoscope (just moved house so many things still packed) seems to be either cyl 1 or 3. The noise isn't constant, it comes and goes still so I think maybe check valve inside lifter is either faulty or a bit of dirt or something got into it (hopefully is nothing more drastic). Anyway, it will give me something to do on a weekend soon, although I would rather use the Disco to go exploring.

Try listening to the EVAP purge valve and check it's clamped correctly.