i have the chance to buy aset of v4 sti heads at a good price, the guy that has them isnt sure if they have bee skimmed before or not, is there away of telling?

while we are at it what sort of bhp can a standard sti crank take and would it weaken it much if it was reground?

 

The standard head height is 127.5mm and the grinding limit is 0.012", so you can work back from that when the heads have been measured.
The crank is not normally an issue - its the rods which are the limiting factor.
IMHO - dont even consider a re-ground crank, you can never be 100% sure the oil gallerys are clean/free of machining swarf and a new genuine Subaru crank is fairly cheap.

Mick

 

As merlin says, DO NOT regrind a Subaru crank!!! - get a brand new one! This is advice from APIDavid, and what he doesn't know about Subaru engines isn't worth knowing.