[Myron Piatek]

To elaborate a bit on what Art said, slight variations in OEM blocks can change the contact points. People bush and correct lifter bores because they are not always at the exact same angle.

While it takes a little labor, but little or no cost if you have the originals, breaking in lifters with OEM or other low pressure valve springs works well. Then you replace them with the high pressure springs you will race with.

I never did it any other way. It's just a matter of how anal/cautious you want to be. I'm not saying it won't work. But it's just not quite the same.