Hi all. Now that I have the heads off (3964290 heads) , I see that the previous owner had bronze liners pressed into the valve guides. These are what have been causing my smoking problem. The heads and pistons, and the back side of the intake valves are caked with carbon.
I have decided on the exhaust side, to open up the existing guides and install bronze inserts. The inserts have an o.d. of .502. I have the core drill, reamer and am ordering the bronze reamer to cut the finish i.d. thru the insert.
On the intake side, I was just going to r&r the entire insert, going back in with a replacement bronze insert, until I came across this article. If I'm reading this right, if I install concentric replacement guides in the head, then the centerline of the guide may not be concentric with the centerline of the seat. I am wondering, if I should just go ahead and install the bronze inserts on the intake side also.
Has anyone had any experience with installing new guides on these heads, and was there a problem with seat/guide concentricity?
Thanks, Jim
Hastings Article (http://www.hastingsmfg.com/Service%20Tips/chevrolet_396_and_427_valve_guid.htm)

well for me i just leave this stuff up to the machinist and let him do it all. around here they charge like 2.50 for stock guides and 5 bucks to put them in each. and that includes regrinding the valves and seats. so for about 120 bucks its a good trade off. besides the machinists i talk to around dont like to mess with bronze guides specially if the motor is going to see alot of street miles. they see no reason why to mess with something that has worked for alot of years for the manufactures to made the heads. and i still run stock guides even in 10 sec motors........ with out any problems......

maybe i'm missing something to why to run bronze guides or liners.......the machinists dont seem to understand why to run them either.....but you know these guys are old timmers.....they stick to what works.........so i just go along with them.........

Jim,
Anytime a guide is replaced, whether it is cast iron replacement or bronze, the valve must be reground. Just a few thousanths of an inch runout can cause serious problems. The valve guide not only supports and directs the valve (hence the appropriate name "valve guide"), but it also locates the valve grinding stones or cutters. A valve cycles many thousands of times even at "normal" RPM levels. Since the valve also rotates during operation, if the valve and seat are not exactly concentric each time the valve closes in a different position (which may be higher or lower than the previous position) the force acts like a lever and actually bends the valve head very slightly. After a few thousand cycles of this the head of the valve breaks off and we all know what that results in.

A good quality manganese bronze valve guide will hold the ID dimension much closer than a cast iron guide, regardless of engine/valve stem temperature. This is the reason why they are used in all-out racing application, however they are not necessary (or cost effective) in a street or street/strip engine.