Back-cut valves

[structured]

Can anybody on here give me some input based on real life experience? I've read a lot about back-cutting valves and I am trying to get my machinist to do it. He agreed to do the intake side, but he says that he doesn't think it is a good idea to do it to the exhaust valves. Says that they are too thin or something. So, has anybody had their exhaust valves back-cut? Do you have pictures? Do you think that it was worthwhile?

Thanks.

[rcfanatic]

I've had mine done. It's a normal cut in a 3-angle valve job. If your valve margins are too thin you'll want to buy new valves

[structured]

What is too thin? I'm trying to decide whether or not I should get new valves.

[rcfanatic]

Not sure off the top of my head but the Bentley manual has the spec. I wouldn't go much under what they spec, maybe a few thousandths