Earlie A
Well-Known Member
Here's an interesting comparison of 4 tests on Trick Flow Ports. Two are with a 2.02 valve and two are with a 2.08 valve. There are many points to be made here, but I'll start with three.
First, look at test 1231 in green, which is a totally stock port. This port at 308 cfm is the highest flowing stock TF port I have tested. Most others I have tested peaked at 285-295. The next test, 1232 in black shows what happens when the pushrod pinch is opened from 2 sq inches to 2.3 sq inches. There were no other changes. Particularly note 0.300 lift, 0.400 lift and anything past 0.600 lift. The effect on high lift is contrary to normal (logical) thinking, but is a result of flow separation on the short side. Opening the pushrod pinch decreased the air velocity at the apex of the short turn, which increases pressure at that point (this is Bernoulli - higher velocity/lower pressure and vice versa). The higher pressure at the apex actually increases flow separation downstream, which shuts down the flow area and reduces flow. Put another way, opening the pushrod pinch made the turbulence on the short side increase causing less area for good flow. The Bernoulli principle and the effects of flow separation are important when trying to figure out what's going on in a port. Don't know if we'll be able to do it, but I would love to run a dyno test with only this change. I think the heads with the larger pushrod pinch would make more power, in spite of the flow curve looking much worse. When you hear the phrase 'the flow bench is lying to you', this is one of the reasons (even though the bench is giving perfectly good data).
Point two will be short. The change to a 2.08 valve along with deshrouding in the chamber and apex/short turn work really picks up the mid lift flow. The TF heads are really strong in the mid lift area. Part of this is the effect of the 'anti-swirl' port configuration. I think this configuration also limits high lift flow.
Point three is to compare test 1434 in red to test 1461 in purple. There were several changes to the port during this time, but most of them had to do with lowering and widening the apex to try to eliminate the nose-over or back-up in the flow curve (test 1434 peaks at 317 cfm, then noses over at higher lift). What I am trying to demonstrate here is what happens when the apex is lowered, the short turn is laid back and the corners of the apex are squared up. Curve 1461 is a 'prettier' curve, but would it outperform curve 1434? This is something else I would love to test.
Point four of three. Some (sometimes all) of the nose-over goes away when a manifold is attached to the heads instead of an entry plate.
First, look at test 1231 in green, which is a totally stock port. This port at 308 cfm is the highest flowing stock TF port I have tested. Most others I have tested peaked at 285-295. The next test, 1232 in black shows what happens when the pushrod pinch is opened from 2 sq inches to 2.3 sq inches. There were no other changes. Particularly note 0.300 lift, 0.400 lift and anything past 0.600 lift. The effect on high lift is contrary to normal (logical) thinking, but is a result of flow separation on the short side. Opening the pushrod pinch decreased the air velocity at the apex of the short turn, which increases pressure at that point (this is Bernoulli - higher velocity/lower pressure and vice versa). The higher pressure at the apex actually increases flow separation downstream, which shuts down the flow area and reduces flow. Put another way, opening the pushrod pinch made the turbulence on the short side increase causing less area for good flow. The Bernoulli principle and the effects of flow separation are important when trying to figure out what's going on in a port. Don't know if we'll be able to do it, but I would love to run a dyno test with only this change. I think the heads with the larger pushrod pinch would make more power, in spite of the flow curve looking much worse. When you hear the phrase 'the flow bench is lying to you', this is one of the reasons (even though the bench is giving perfectly good data).
Point two will be short. The change to a 2.08 valve along with deshrouding in the chamber and apex/short turn work really picks up the mid lift flow. The TF heads are really strong in the mid lift area. Part of this is the effect of the 'anti-swirl' port configuration. I think this configuration also limits high lift flow.
Point three is to compare test 1434 in red to test 1461 in purple. There were several changes to the port during this time, but most of them had to do with lowering and widening the apex to try to eliminate the nose-over or back-up in the flow curve (test 1434 peaks at 317 cfm, then noses over at higher lift). What I am trying to demonstrate here is what happens when the apex is lowered, the short turn is laid back and the corners of the apex are squared up. Curve 1461 is a 'prettier' curve, but would it outperform curve 1434? This is something else I would love to test.
Point four of three. Some (sometimes all) of the nose-over goes away when a manifold is attached to the heads instead of an entry plate.
