Yeah, relacement, if they are cracked, they could leak.
Not a problem. Just make sure the others are ok, get as much as you can done with them and take them to a machine shop to get 2 new guides pressed in. Make sure they ream them and cut the seats in too. All you'll have to do is to lightly lap them valves in after that.
Shouldn't cost much, what 2 guides fitted etc. Maybe £20- £30? Advise on using steel guides.
i felt inside each guide with a thin screwdriver and u cant feel or see any cracks
i can only feel the bit on the rim from the top side of teh guide
is it possible its maybe just a mark made when taking the stem seals off ?
if not i suppose may as well have the head skimmed too ?
lol, i meant i cant see any crack on the inside or outside, just a mark on the top of the guide, like the lip you'd maybe call it
i wasnt sure about this one at all so i took it to my dad's mechanic mate whos assured me its ok
took ages to get those first collets back on but got a technique sussed and went well after that