api built engine, v9 crank,rods and cams with CP forged pistons - piston slap still present when warm, is this a cause for concern?

 

How warm is warm?

 

When completely warm during idle it might still be a bit, at least mine does a bit. Found that it depends on the oil you use as well. For winter I used 5w40 motul, but in summer i use 15W50 motul. With the latter there is no slap once warmed up, not even during idle.

 

My 2.1 slaps a bit when it's cold, but is silent when warm.

Sure it's not something like the cambelt tensioner?

 

warm as in still there when the car is running at normal temp can hear over exhaust.

 

Mine still slaps when fully warm but iv been told it's down to the piston tollerances and once iv got it very hot they tend to quieten right down then , had it mapped like it and the mapper said it sounds fine