For port matching and bowl work, I use long-cut smaller diameter round-nosed cylinders for 80% of it. The blending angles are much easier to control as well as surface waviness. Final blending is a third the effort than when using a curved-shape cutter (egg, flame, etc.). In the bowls, I use the RN-CYL again and ball-end cutters for the bowl radius and back cutting of the guide radius. If all I had was a long length-of-
cut RN-CYL (as long as I could get) and a couple small balls and maybe one small egg I'd be okay. If I'm doing full runner porting I'll use many different cutters from the box. That's a different ballgame. Chambers get the same tools except the RN-CYL is larger diameter.
Opinions you didn't ask for but may help: Use two hands and hug the tool for stability when possible, moving your whole body to move the tool with light pressure. Use lower tool and travel speeds to avoid hopping, skipping and waviness and light pressure to let the cutter do the work without gouging or grooving. Pretend you're a CNC mill. A head jig is
very useful and avoids a lot muscle cramping as well as making blending angles much easier to get accurate. Do a little on each port and go back to the first to do more and repeat. Doing one port all the way ensures different ports. Oh, and less is often more.
At the minimum, get a shop vac sucked-up to your valve seat and a sensitive vacuum gauge with a thin tube to probe the runner for sudden pressure changes that need blending. Not removal - just blending. Like the lady said - size doesn't matter, smooth technique does.
FWIW,
David
Today
