My 16valve Coupe with 141,000 on the clock makes a horrible clattering noise , it sounds like a ford diesel ! The car runs fine with 170psi compression in each cylinder . I know this problem is common with 16 valves as my mate had one with 60,000 genuine miles on the clock , full service history etc which sounded worse than mine but went like stink up to the day he sold it years later with the same noise !Before I plan to take the head off please could I have some advice with what the likely problem is and why is this common to 16 valves and not the 20 valvers with twice the mileage etc .The noise does not go away and is present throughout the rev range but more disguised by exhaust noise etc I have been told to lap the valves to the seats but this will only be good for up to 10,000 miles and then need doing again ! why? Could it be the chain linking the cam shafts ?If its the valves why such good compression ?Is it just the hydraulic buckets but if so why not on other engines ?How about the cams , lobe wear maybe ?What is so unique to the 16 valve engine to make such a racket . The car is in superb overall condition but the noise really lets it and me down . Please can you shed some light on this or has somebody rectified the same problem , thank you.