The Dark Side of Will wrote: ↑Thu Mar 09, 2023 7:37 pm
ericjon262 wrote: ↑Thu Mar 09, 2023 2:10 pm
The Dark Side of Will wrote: ↑Tue Mar 07, 2023 10:11 pm
The throttle opening is obstructed by the throttle shaft, even at WOT... The same diameter bore is not an obstruction
dyno tests have shown that ports being stepped slightly smaller upstream make almost no difference in power, but stepped slightly smaller downstream can cause a not insignificant reduction in power.
Talking about intake ports?
A well-designed "port", which includes both the metal in the cylinder head and the metal/plastic of the intake manifold, tapers and thus accelerates the air it it travels toward the MCSA and valve seat. The edge discontinuities matter more at higher flow speeds.
I agree, but taper=/= step. A step down in cross section will cause a turbulent front ahead of the step, which will also partially obstruct flow in the port/runner/pipe, a step up in cross section causes a small turbulent area downstream, behind the step, and not into the bulk flow. in a perfect world, you don't have steps, or the steps are designed to create a thin boundary layer. What I'm referring to only occurs at joints, like the TB to manifold, or intake to head, and isn't necessarily a port design, but a function of available engineering tolerances
a simplified infographic.
The Dark Side of Will wrote: ↑Thu Mar 09, 2023 7:37 pm
ericjon262 wrote: ↑Thu Mar 09, 2023 2:10 pm
it's also a TBI 350 for a Suburban. I'm definitely not setting it back up in the mill to redo it,
No, you have to CNC it
I mean, how do you think I did it this time? setting a intake up on a mill, manual or CNC, has it's complications though, especially when the bores being machined aren't perpendicular to the flat surfaces on the underside of the manifold. it wasn't impossibly hard, but it was a bit of work I don't care to repeat.
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