[freebeard]

As for the cylinder head thing, that's something I haven't really been able to work out well. You can port and polish, but where is the stopping point?

Three angle valve grind is pretty straightforward. Porting and polishing is a black art, at least it was in the mid-1950s.. Rough finish in some areas prefered.

Today we have extrude honing.

https://www.extrudehoneafm.com › ind...50; automotive
Automotive - Extrude Hone AFM
This makes Extrude Hone AFM's contribution complete: better performance, better fuel efficiency, and cleaner exhaust emissions. Bring Us Your Components Today If you are interested in using the AFM process to improve combustion and efficiency, we recommend starting with the intake manifold.

https://www.extrudehoneafm.com › ser...n-charlotte-nc
Extrude Hone Porting in Charlotte NC - Extrude Hone AFM
Extrude hone porting in Charlotte NC can deliver many benefits for any passage that gas or liquid will be flowing through. The most commonly ported parts are intake and exhaust manifolds, but we can also port engine heads, turbo impellers, housings and pumps, and 2 or 4 stroke cylinders.

https://www.speed-talk.com › forum ›...ic.php?t=25856
Extrude Honed Intake Manifolds - Don Terrill's Speed-Talk
The problem is greatly exacerbated in a dual plane intake with it's sharp 90* turns. Next intake, you'd be well advised to follow joes advice. Even if you hand port it yourself, you stand to gain far more than the extrudehone. You'll have the ability to direct the air where you want it. Extrudehone was just an easy money fad back in the day.