how does milling the cylinder head affect the valve timing??

[Bru]

Here are some photos of a uncut and a cut head. The more you cut a head the flatter that rounded part under the thermostat standpipe connection gets. It's something to look for when buying a head. I had my head and block resurfaced and ended up using an old school metal shim gasket under the Toyota factory gasket. I sprayed the bottom of the shim gasket That contacts the block with Prematex copper spray. After 7 years and 35K miles, I haven't had any issues. Alternatively, you could use a thicker stacked metal head gasket alone but you really need to prepare the surfaces first. Here is a link to a company that can supply most any thickness of shim gasket you want. I wouldn't go of more than 0.040" though. It's been discussed in other forums that a 0.020" cut is a small fraction of a degree out of timing. The Toyota manual allows 0.010 but doesn't say anything more than that.

Innovative machine & supply: https://innomach.com/cylinder-head-shims