I've spent a little more time with the TF head on the bench, and while I know these are a good OOTB head, they are still a hot mess. I am very surprised they flow 280-290 cfm. There is turbulence almost everywhere except right down the center of the port. Along the walls of both sides of the bowl there are wide areas of ZERO flow. And my experience has been that when the pitot is stable at 0.0, the flow is usually reversed. CFM readings are unstable, ranging from 275-305 cfm. Depression is hard to control - bounces around about 1" H2O. The ports still need a little massaging to be right.
The PRP is very intrusive on these heads and I think it's the source of lots of the problems. There is also precious little metal to work with at the PRP. The head bolt bulge is also a bit of an issue.
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