I want to test the cams performance when degreed. I need to lower my powerband because the car is too laggy now. The question is - how can I make sure a valve doesn't hit a piston.

I have Delta K272 (same as Kelford 272) pair, Manley 8.5:1 pistons, Cometic MLS 1.6mm gasket, head and block surfaced.

You can't adjust the cams too far so that the valves make contact with the pistons. It takes at LEAST 3 teeth off in order to start thinking about contact to happen. Each tooth = 6*, so you would have to adjust your cam gears a MINIMUM of 18* one way or another in order to make contact. Don't worry about it.

Does this apply to stock cams?

K272s have a very aggressive ramp rate and a max lift of 11mm so I thought that advancing with 12 degrees may be risky

4G63 Camshaft Degreeing
From there, you should have some room either way. The best bet would be to clay the clearance, but you should have a few degrees to play with.

Why did you go with such an aggressive cam if you're worried about the lag?

The HTA68 should be a quick spooling turbo.

I got those along with the adjustable cams so I can still have aggressive cams and lower the power band thus lag, which I guess was wrong.

I will try degreeing them and see what happens. If I can't reduce lag significantly will put back the stock cams.