Interference with +1mm alves and ST 8.6 pistons
 

Based on my initial engine build research I was not expecting to have interference with my Manley +1mm intake valves, Supertech Inconel +1mm exhaust valves, Supertech 8.6 pistons, stock VVT cams, Mazda 99-00 head gasket and 0.010" head shave. I just did a quick rotation check with the intake and exhaust valves open on each cylinder and the pistons touch the valves on each cylinder on the intake valves and just barely on cylinder 3 and 4 exhaust valves. Exhaust valves on cylinders 1 and 2 just barely clear.

I was not expecting my setup to become an interference engine with only 0.010" shaved off the head. Is this interference to be expected or should I look for something I might have screwed up during assembly?

Can you post a picture of where the valves are touching the pistons? Sometimes the pistons require a small chamfer on the outside edge of the valve relief.

It's pretty common for built motors (or even stock NB motors with a resurfaced head) to be interference. Here are examples. Just make sure you time your engine right and don't break a timing belt :)

If you're really paranoid, you can always try measuring P-V clearance with the timing belt on. If you intentionally mis-time the intake cam by three teeth, this will let you check P-V clearance at max VVT advance.

Sounds like this is just "interference motor," not an actual lack of P-V clearance that would need any mods to run safely.

I can accept that it now is an interference engine. Running blue gates belt and will keep up with belt replacement to avoid timing belt breakage.

The head is bolted down so I really don't want to open it back up to modify the pistons.

I understood that, just thought if the head was not bolted down then maybe the pistons could be modified so that it would remain a non-interference. Will be building a new engine next week with ST pistons and 1+ exhaust valves. I will check this and see if it is possible.