SBM Port Molds

I got the wife and cats out of the bunker now that things have settled down a bit.

Here's a few latest thoughts and questions about the TF head design. I've been spending a fair amount of time porting and testing one intake port on a Speedmaster SBM head. I have been able to get the head to consistently flow 280 cfm without going overly large on the cross sectional area or the port volume. I would call it a decent port at this point. The part I still have to figure out is the SSR. That was my real interest in the TF heads. I was most interested to see how TF handled the short side to get the flow up to 300 cfm. That is why I was surprised when I saw the bowl/guide area.

The TF does seem to have a slightly taller SSR apex height than the Edelbrock/SM head. This allows for a larger radius on the short side, which helps keep flow attached to the short side at higher velocities/higher lifts. So that is part of the TF improvement over the Edelbrock/SM.

On the SM head I have also been using a pitot tube to measure velocities around the perimeter of the intake valve from the combustion chamber side. This has given me some understanding of how the air exits the valve into the chamber. At higher lifts and high cfm, the air flow around the short side and the shrouded side of the valve starts to suffer. This is the area that TF seems to have targeted with the twisted port design downstream of the guide. As NBT described in an earlier post, the TF engineers have layered the air. The port section on the cylinder wall side of the guide is high arching then curves quickly to force air down into the area of the SSR and the shrouded section of the valve. The air passing on the cylinder center side of the guide is kept much lower and straighter. This high velocity air is shot over the valve and twisted around to the far side of the valve in a way that makes it collide with the natural swirl direction. I haven't have the head on the bench yet or tried the string in the port but I hope to get there over the next week or two.

Here's my confusion and questions. I can see how the dry flow on a flow bench can be improved with these changes. Wet flow with fuel is a different story. Fuel (especially the big drops) wants to travel in a straight line. How does the fuel react to all these twists and turns? Does a TF head perform any better than a max effort ported Edelbrock? Not much info out there that I could find. I have found some reference to a TF engine liking 30-32 degrees of timing. That would indicate a more efficient burn than the normal 36ish degree SBM engine.

Thoughts are welcome, but I really don't want to sleep in the bunker again tonight.