100-4 valve replacement

[JTSchmid]

Hi,

Does anyone out there know the "installed height" for the valves in a 100-4 head. I'm rebuilding the head and installing new seats and need to bring the valves spec back to original. The height I need is from the spring seat to the top of the valve.

Regards,

Jim

 

[roscoe]

Jim,
I'm not sure that is a number you can come by unless you actually measure it from your old valves and seats. I may be missing something, but that number would vary by quite a bit depending on how the seats are cut and how the valves are gound. That, of course is part of the reason why we have adjustable rocker arms. If you are fitting valves that are from another application, you need to pick something close to the same height, but it would seem to me that is long as you are somewhere in the middle of the valve adjustment range you can't be too far wrong. I do have an old head and some old valves, so if you really need this number (perhaps you have pulled the old seats out already and are using non standard valves?) I can go stuff a few valves in and make a measurement for you. OK, what am I missing?

 

[JTSchmid]

Jon,

There is a depth from the factory to which all the seats were ground and a depth to which all the valve spring seats were machined leaving a height that when the valves were installed was a standard or what is called the "installed heigth", that being done, it gave you the same spring tention throughout the valve train. What I am after is that length when the heads were new. I've got an old head but the seats have been ground at some time in its life leaving a longer length and thus less spring tension. I can accomplish some of the same results with valve spring shims but if I can get that length, shims will not be necessary. I hope this make more sense. The measurement is from the bottom or valve spring seat to the top of the valve stem.

Jim