Clacking lifter noise

[ianrandom]

Would anybody be able to give me a rough cost estimate of what finding and replacing a clacking lifter would be? Its an '86 420SE. Runs great, just clacks every now and then on start up, definitely lifter noise.

 

[ianrandom]

Just feeding back with advice from another site. Citric oil flush worked to remove gunge, run through the engine for about 10 mins before oil and filter change. Also prior to that a few gentle miles with ATF 700ml-ish added to the oil, also hopefullly removing gunge.
Noise is much better now, still something there but much quieter and not for as long.