What is the biggest valve lift a factory head can handle?

[robk46]

Came across a thread that states the stock head can only handle .420 lift. The 204/214 cam is rated at .442 intake and .472 exhaust. . . I always thought if you stayed under .500, you were OK?

http://store.summitracing.com/partdetail.asp?part=EDL-5487&autoview=sku

 

[charlief1]

http://www.turbobuick.com/forums/general-turbo-buick-tech/47058-valve-lift.html
About what I stated. Clearance from the top of the guide to the bottom of the keeper I measured at .4885 on the exhaust. Leaves you .0165 and that's just not enough for me.