The porting areas that are imperative if one takes on such task are from valve throat/seat (where the poppet sits at rest) all the way to base of the pellet, assuming you do not have a retracting bolt probe.
The main areas of focus would be.
1) Valve throat / seat (one must consider the surface area of the poppet stem that occupies this orifice)
2) Valve exit port
3) The transfer port
4) The barrel port
5) The bolt probe present within the barrel
It takes just a few rather simple CSA (Cross-Sectional Area) calculations. A lot of tuners have their own methods to this madness, such as having the porting reduce incrementally from port job 1 through port job 5, while others such as myself try to keep all things equal, aside from port job 1 and 5 where there are obstacles (valve stem and bolt probe) that cause a surface boundary layer around themselves, reducing the effective porting, which means I take port job 1 and 5 to an additional 5% CSA over port job 2, 3 and 4.
I have a bunch of CSA formulas I have developed over the years, such as one that takes your forward porting (2-4) and valve stem diameter present in the throat and gives an optimal Valve throat / seat diameter. Here is an example of that, which gives 5% extra CSA to compensate for the boundary layer I mention above.
(2*SQRT((3.1415*(PortOD/2)^2+3.1415*((StemOD)/2)^2)/3.1415)*1.05)
I do have pictures, but those are from early port jobs that I have since polished and / or redone and would be quite embarrassed to post the old, crude jobs, and am far too lazy to tear down my pcp now to snap pictures from port job 1 through 5.
-Matt
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