Here are a few thoughts on a few different fronts.
If someone is building a high rpm 340/360 or a stout street 408/416 and budget is a consideration, these are a great option out of the box. Maybe the best option for the money. In my opinion ported Edelbrocks or Speedmasters could be just as good, but it takes a lot of work to get them there. The TF has a nice valve job with valves already back cut. The throat size is 89%-90% which leaves a little wiggle room. The fit between the valve and guide is right. The combustion chamber design seems better than the other options. It's a nice head.
With that said, I was a little disappointed with them. That is probably a result of my expectations being too high or misguided from the beginning. I'm not knocking the TF's - these are nice heads. But I was hoping to have an aha moment with the TF that would help me fix the flow issues that I experience on all SBM heads I've played with so far - flow separation and back up above 0.550 or 0.600 lift. But, it seems that TF suffers from the same issues. I'm sure a little clean up work around the guide and in the bowl would help. I suspect there is flow to be gained by working on the head bolt bulge and PRP. It would be interesting to know how 50 degree seats would change things. I'm sure this head can go 300-310 cfm with the 2.02 valve. I also think an Edelbrock/Speedmaster can get there. In the end, it seems the tight push rod pinch, low port, 18 degree valve angle and head bolt locations just create some insurmountable issues. You're not going 350 cfm without major changes.
What I have spent the most time thinking about is the anti-swirl port design. I've become more convinced that the twisted bowl is not about fuel shear and not about increasing cfm. I think it is about reducing swirl. Here's my understanding of swirl. In a production car or a low rpm street car swirl can increase low end torque and reduce emissions. In a performance car swirl starts being counterproductive. It takes energy to swirl the air/fuel mixture, and that energy could have otherwise been used to get more air into the chamber. So, high swirl reduces volumetric efficiency. High swirl can also centrifuge the heavy fuel to the cylinder walls, throwing it out of suspension. That creates fuel washing and rich/lean conditions which can cause poor combustion and even detonation. So it seems the reduction in swirl in the TF heads would be a good thing. But look at how the swirl reduction was acheived. It was by forcing the air to go where it does not want to go, and by making the air/fuel mixture turn more than natural. In my mind these things are not efficient for dry flow, but even more detrimental to wet flow. I'd really like to see A/B dyno and track testing TF against others. Maybe the design is great for power and performance. I really don't know.
PBR, I know you have extensive experience with the Eddy's and at least some with the TF (maybe a lot). What's your opinion of the performance potential of both?
