I looked through the archive and found this from Abe Crombie. My question is " I think I have the more harmfull knock" what is it ????

"Re: 91-740 wagon𖛊/1995] posted by abe crombie on

Sunday, 8 March 1998, at 11:20 p.m.

The piston has the wrist pin passing through it and the metal is much thicker in that axis than on the skirt axis. Since there is more metal there is more expansion and the goal is to have a perfectly round piston AT OPERATING TEMPERATURE. The engine spends so little time at cold temps that this is an annoyance but is not detrimental to the engine as long as it occurs only for 1-4 minutes on start up when engine is cold. A potentially harmful knock would be one that does not go away or is present only when you abruptly increase the throttle."

A "potentially harmful knock", e.g. one "that does not go away or is present only when you abruptly increase the throttle" is most likely to be caused by worn connecting rod bearings, or less likely, worn main bearings. Too much clearance causes the noise; an accompanying symptom is low oil pressure. Hence, an oil pressure check can assist with diagnosis.

Normal piston slap often sounds like noisy valves to a new Volvo owner. (That was my personal experience, anyway.) A check of valve clearances may be a good idea, if only to rule out valve train noise.

Try to narrow down the problem, if indeed there is one, before tearing the engine down.