The GX head I'm currently using on my A12 has had 2.5mm milled of of it. With the GX cam it's not an issue. I'm getting ready to assemble an A15 and will try to use my forged flat tops, obviously dependent on the camshaft may be an issue. I'm pretty sure I'm going to need valve reliefs cut into the pistons.

The Datsun Cherry race prep manual says to mill the head upwards of 1.8mm and use the .8mm head gasket versus 1.2mm So using my normal 1.2 would get me an extra .4mm that takes it out to 2.2mm less than standard.

Any one ever run a head this thin with A15 and race cam?

The damaged head is standard thickness but given how close the damage is to the valve seat I'm not sure that is repairable.

So I took some measurements; with 2.5mm milled off the head and using flat top pistons the most aggressive cam you can run is a GX spec camshaft.

I've since valve notched the forged JE pistons I have by 2.5 mm. I will be using the standard method of putting clay on top of the pistons to see which camshafts will still be safe to run. I have one that's 278 duration with .420 valve lift (this is what I was using) and the other is 286 duration with .460 lift. I will be trying those tomorrow, if I don't get it done then it will have to wait a few days as it may be as hot as 110 degrees on Wednesday and Thursday.