Re: 5000CSQT head mods...

[Hulda Jowett <hjowett@mcla.mass.edu>]

About 75% of flow gains come from the last 30% of the port. Work around 
the seats is most important. The first and most easy to mod is the area 
where the port meets the valve seat. There is usually quite a mismatch, 
and it is easily smoothed. The next two are a bit more involved, and 
require a machine shop to perform. Unshrouding around the valves in the 
combustion chamber really helps low lift flow, and thus bolsters low end 
performance. The 3 angle valve job works well too, but can cost longevity 
of the components.

Then, a basic smoothing of the casting ridges in the main portion of the 
port helps just a little. You don't even want to think about reshaping 
the port! That type of work requires a flow bench. 

Further gains can be had by going the factory route of 7mm valve stems.

All in all though, these gains are much more prevalent (sp?) on a 
normally aspirated engine, but will show some gain on a 
turbo/supercharged engine. Most you can do, or have done for you by a 
local machine shop. You'll have a good all around head.

Later,

Brian