My '63 Corvette (I'm the original owner.) has - or I should say "had" because they have been rebuilt with sleeves - integral valve guides as do all cast iron head small and big block Chevrolet V-8s and all other domestic engines with iron heads. As far as I know all the I-6 Chevy engines also had OE integral iron valve guides, but it would be rare to find one today that hasn't had some kind of valve guide rebuild done.

Integral cast iron valve guides give reasonable wear and are obviously cheap, because it's just a machining operation on the transfer line, but they are more expensive to rebuild. Aluminum heads with bronze guides are more expensive to build by the OE, but they are probably cheaper to rebuild because very little labor is required to replace them. New bronze guides are no more expensive than sleeve kits for iron heads, but iron heads must be machined oversize first and then the repair kit installed and reamed.

Once an aluminum head comes out of the oven it only takes a couple of minutes to swap the guides and another couple of minutes to ream them after the head has cooled to room temperature.

A couple of years ago I watched the machinist replace the valve guides on my Cosworth Vega cylinder head. (He also owns a CV and had just rebuilt his head.) It was a piece of cake. The guy is a real pro. There's nothing like having the proper tools and lots of experience. A good part of his work is Merc and BMW heads, so if my 2.6 head ever need to be rebuilt, I know who's going to do it.

Duke