Spark knock happens under load, like pulling a hill at full throttle with the engine lugged down. What kind of sophisticated computerized engine analyzer are you using that isolates a spark knock to specific cylinders?

Valve lash has a habit of tightening up as the engine reaches full operating temperature. I like to do a cold companion cylinder adjustment with the lash set .001" over specification on the intakes and .002" over on the exhaust, then do a 30 minute test drive and check and tweak the clearance as necessary with the engine fully warmed up.
Jerry



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