Thanks a lot Richard for the explanation👍👍If you are building a all out race engine that will not be driven on the street his porting is still too large a diameter. Smaller ports improve intake charge speed increasing volumn into the chamber. Modern porting only involves smoothing the terrible casting roughness and 1st bulge in the top. And opening the sides about 2mm on each side starting about 1" before the guide area and straightening the area from that to the valve seat area. The taper into the guide projection is functional, but can be narrowed.
Guides should be shortened, Intake shortened 5mm and exh 3mm. Set to a total 11mm exposure above the floor of the spring floor.
If you are not concerned with low and mid range open it as in his pics.
But the highly modified race heads use higher smaller (sleeved) ports.
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You can see port constriction in the area of the guide to seat area
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Exh after port work
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Intake after porting and with Weber intake port matched (and it needed it)
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Head waitinmg on custom Titanium valves being made to fit my 13+mm lift intake and 12.8mm exh cam