can i swap my old vavles out for performance ones?

[hellboy006]

so im thinking about buying a stock rebuilt head for my ka24e, the thing is i want to swap out the cam, vavles, springs, and retainers with some high performance stuff.. but i was reading somewhere that each valve guide has to be machined to perfectly fit each valve... like there are differences in the valve stem thickness from valve to valve... so if this was true then it might be a bad idea to buy some ferra or si valves and just stick them in the new head... sounds kinda sketchy to me, dont know if there is much truth to it.

[pwrofdrm]

If the head is out and you're replacing everything anyway, just purchase some new bronze valve guides. They'll match up just fine with your new valves. Then you have nothing to worry about. That's the right way to do it. But, you really don't have much to worry about by just replacing the valves and not touching the valve guides, so long as they're not worn.

[hellboy006]

well from what i understand, the head im thinking about buying had new valve guides installed when it was being rebuilt.. so thats cool i guess.. i'd do it myself but dont you have to heat the head to press the guides in and so on? i cant do that in my garage.

thanks for the input, i guess ill go ahead and buy it.

but what do you think.. is replacing the stock valves with si valves even worth it?