Evening all, looking for some advise on the normal crossflow valve to piston clearance at TDC.

I have pockets machined into the pistons currently 0.50mm clearance between valve and piston at TDC. Does anyone know a round about figure I know this changes depending on cam etc...

Burton are saying 1.5mm minimum as are a lot of places however looking on piper and Kent technical sections they are saying around 0.5mm?

Help please,

As a xflow user, i would go with the 1.5mm as per Burtons, .5mm seems a very small gap ?

On the Pinto clearance should be .75 to .9mm depending on peak revs due to rod stretch
It will be the same for the Crossflow

im sure we used to do it at 25 thou 0.635mm ????