What burrs are you using, Joe? What about sanding rolls; any grit progression?
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On iron heads, I use a variety of stones, burrs, cartridge rolls, and sanding flappers. After scribing the ports, I also scribe the pushrod tube holes so I know how close I am to those. I usually start with the intake bowls first, then intake ports, and finally short turn, then exhausts the same progression. Combustion chambers last. I cut the valve guide bosses first to establish the curvature of the bowl and area/distance between the guide and roof walls. I do this first so I can control the amount of material removed to be safe and not grind a hole. I usually use a carbide ball to establish this radius and distance. Smaller ball on the tight side, and larger ball on the swirl side. Next I use stones in various sizes and shapes to remove all the metal I want all the way out to the seat and back out to the port opening. Always, always work from the innermost point out to the seat or port opening. If you start at the gasket and go in, you will make a mess. Next I use carbides to smooth up the stone marks, and get the rough size and shape I want. Some porters want to leave a rough carbide burr finish, but I prefer to go the extra steps and finish the ports with a #50 cartridge roll finish on the intake ports, and polish the exhaust ports with a 100-120 grit cartridge roll. I use 36 to 60 to 80 grit to get all the sides and floor the final shape I want, then finish the ports with a 6" mandrel and 50 grit cartridge roll. After that, I use another mandrel with slot and piece of crocus sanding roll cloth at 50 grit to flap the entire port to remove any irregularities and stray cartridge roll marks. I polish the exhaust ports the same way with a 120 grit flapper crocus cloth.
I studied with a master porter who supplied Ford heads for competition in SCCA mustangs, and Buick heads for the GTP race cars back in the late '80s and early '90s and did my first flow bench work while working at that shop. I have been a one man shop for the last 30 years, working with several local machine shops and racing shops. I built a shop at home 21 years ago, and have my own SF-600 flow bench, porting booth with dust collection ability, and enough equipment to assemble all my engines, and work on my own vehicles with a lift.
Here are a few of the tools used to port heads and intake manifolds. Joe-JDC
