There is another little trick. With the valve springs and seals off run the valve open about 1". Then put a finger over the top of the valve guide. With the tip of the valve stem right at your finger, pull the valve out real quick. If you hear a pop sound then you know your guides are pretty good. No pop means your guides are getting looser because air is getting around the loose valve in the guide. Mike's wiggle the valve test is good to do too.
Can try again with the new valves they should fit tighter than the used ones. Sometimes the end of the used valve stem gets hammered over enough by the rocker arms that they are hard to push back out through the guides.
So stop right there and take some 180 grit emery paper, sand the tip of the valve stem while rotating the valve with your other hand to get the burr off the end so it will easily slide out. Otherwise you will damage the valve guide trying to push the valve out with the burr on the end.
The exhaust valve has a greater tolerance for the expansion due to the hot gasses so they will not "Pop" as loud as the intake valves and guides.
And yes there is a few thousands difference between the intake and exhaust valve stem diameters to deal with the extra heat on the exhaust side.
Most of the times the exhaust guides will wear out first from the extra heat associated with them. Can try the new valves and see if they tighten up within reason.
If not then there is the knurling process that can be done to save the existing guide and get it to tighten up again.
Have done all the exhaust guides by knurling on some heads and all the intake guides were good yet. Just have to see what you have there.
