273 commando valve clearance problem

i`m building a 273 commando for a 65 signet-it`s a restoration so that`s why the 273. i had stainless 1.88 and 1.6 valves put into the heads and now i`ve got valves that hit the cylinder walls-has anyone come across this before? i thought i did my homework and people on forums said only the 2.02 valves would need cylinder fly cut but after mocking up a head on a empty bore i can see the valve hits at .250 open-mainly the exhaust one.
my question-it`s going to run a 470 lift cam- how far down can i cut the relief? pistons are 10.5 egge and they are .082 down the hole.
they have about .200 of land above the top ring.
how close can the relief be to that top ring?
any help really appreciated.
all the best
frank.

I notched a 273 once for 1.92 valve Magnum heads. I just masked it off took a carbide in the die grinder and beveled off the edge.

Worked fine. I used a coffee filter in the cylinder to catch the shavings.

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i`m building a 273 commando for a 65 signet-it`s a restoration so that`s why the 273. i had stainless 1.88 and 1.6 valves put into the heads and now i`ve got valves that hit the cylinder walls-has anyone come across this before? i thought i did my homework and people on forums said only the 2.02 valves would need cylinder fly cut but after mocking up a head on a empty bore i can see the valve hits at .250 open-mainly the exhaust one.
my question-it`s going to run a 470 lift cam- how far down can i cut the relief? pistons are 10.5 egge and they are .082 down the hole.
they have about .200 of land above the top ring.
how close can the relief be to that top ring?
any help really appreciated.
all the best
frank.

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You can also cut down a 1.88 to 1.84 and you won't have the shrouding problem.