With the 37 different posts about 4V heads, 2V heads, quench heads, and open chamber heads, I've lost track of which ones you have...LOL
If they haven't been machined/freshened up, I would just have your machinist measure the install height. The jist of is that you put the valve in and use a valve spring micrometer with a retainer and locks to see how much room there is between the spring seat and the retainer. Any competent shop should have one, or you can buy your own for about $15 from somewhere like Jegs/Summit, etc. Manipulation of that install height, whether it be with shims, +/- .050" locks, etc, etc. will change the way the spring functions and what spring pressures it will have. Some factory heads (over the period of 30-40 years) could have been cut on to make the spring seats larger, etc. All of this will affect the height of the spring once installed. A spring that's .030" taller could have 15 lbs less pressure (just as an example).
Also, if no machine work has been done (depending on what head you have), you may want to ask them to cut the valve guide bosses down so that you have plenty of clearance between the valve seal and the retainer...it will also allow you to run the most common sizes of valve seals.
If they have been machined, then you may want to look into buying a mic for yourself. They're cheap and are a good tool to have in the box.
B2 Motorsports, LLC
This message has been edited by blykins from IP address 22.214.171.124 on Sep 13, 2011 9:36 AM