Assessing valve guide wear.
 

I am in the process of checking my valve guides. I borrowed a real nice inside bore gauge from a machinist buddy, I have measured 4 out of 6 heads, and all of my valve to guide clearances fall into the .0035-.0040 range. The specs I have are Intake= .0011-.0059, and Exhaust .0019-.0078.
I am sort of looking for a go- no go answer here. I have no problem spending for a valve job, but these heads were definately done at some point recently, the car has less than 80,000 miles, and the leakdown #s were pretty good when I checked it before teardown.

Take them to the shop and tell the machinist to change guides as necessary. I leave the judgement to him because he recognizes the wear and spec.
I never have a problem with his decision.
Bruce

The problem is they become oval in shape, side to side may be fine but front to back may not? And they usually open up in the port area which causes exhaust to escape into the valve stem

I agree. Let the machinist buddy decide. That's his forte.

I have done a "few " valve jobs..they are not out of the way that hard to do...if you want to purchase the equipment..I am ANILE about proper fits in the valve to seat area..but 1st the guide has to locate the valve to the seat...most every time would be a good thing LOL
SO, once you mess with the guides you have to redo your seats....
back to your stem clearance..I have found that a experianced feel is quicker and better then all the dials in the world for this application