If i get bare heads, do i have to get a valve job to machine the valves seats for the valves? Or are the valve seats already machined and ready for valves?

 

Theoretically, assuming a new head with installed guides and new valves, you shouldn't have to have a valve job unless the angle of the seats does not match the valve (there are other theories about slightly different angles being used but I don't think that is what you're worried about). The suppliers of both products should be able to answer that.

A practical way to check is to put a very thin coating of Prussian Blue paste on the valve. Use a light weight coil spring (available at a hardware store) under the valve and inside the port. Lightly press down the valve and slowly rotate it on the seat. Remove the valve and check to see that there is an even blue marking centered around the seat. If there is not--depending how badly off the mark is--you should have that seat retouched. If it isn't too bad, you could probably get away with lapping the valves in (the same spring comes in handy for that).

I normally lap in the valves even if the head and valves are new.

Hope that helps!

 

So its a good idea to do work on them anyway.

 

I just like knowing that the valve is individually mated to the seat to begin with. (remember to number the ports and valves with a Sharpie) The fine grit valve lapping paste should do the trick on new valves and seats. Don't go crazy with it and make sure you thoroughly clean the head and valves with hot water and detergent (followed by a light spray of WD-40). That grit will do a job on the bearings if you let it get into the engine. Don't let it get into the valve guide while you are actually working on it either.

I've tried a couple different suction-cup, valve-lapping tools and I have gone back to the light spring method I mentioned. Cheap and effective.