So a while back I sent my first prototype tunnel port head to Joe Craine, who had generously offered to port it for me to see what he could get out of it. Joe only worked on the ports in one chamber on the intake, and only finished one chamber on the exhaust, but he was able to come up with some pretty good numbers:
Lift Intake Exhaust (no pipe)
.100" 78 58
.200" 155 114
.300" 227 141
.400" 285 192
.500" 330 212
.600" 357 219
.700" 379 222
.800" 390 230 (260 with pipe)
On the exhaust side, Joe flowed most of the lifts with no pipe, and as seen at the .800" lift level, the pipe definitely helps. My local shop that flowed these heads always uses a pipe on the exhaust, so Joe's numbers are very impressive if that is taken into consideration. Joe also experimented with adding some epoxy to the floor of the exhaust port, which apparently hurt some at first but flow later came back with some more massaging.
Also I really liked Joe's intake port treatment. He did not do any significant enlarging of the port, which is great from a velocity standpoint. The improvements he made picked up 40 cfm from the as-cast numbers that I posted previously. Joe commented that with more work he felt that 400 cfm is easily possible with these heads.
Joe also did some work in the chamber to open up the flow around the valves; it appears from my measurements that he went up to a 4.31 bore size. This certainly helped the flow as well. Bigger bores are always better for breathing.
Here are some pics of the intake and exhaust port. I'm sure if anyone has questions about his work Joe will be happy to chime in and answer - Jay