smaller ports, better?
Has V.I.P in HELL!
Joined: Jan 2004
Posts: 8,987
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i know pro-stock drivers came to that a while back,they found out bigger isn't always better,the big ass vavles ended up getting in the way to much and was killing the volocity and flow numbers.so they started using smaller valves and ports.
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Joined: May 2002
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Since the guy that runs that never bothers to explain the theory behind the advantage of small ports here is all you need to know about them.
INTERTIA STUFFS CYLINDERS !
Most ports are big enough to flow all the air any engine can handle. What port size changes is how fast the air moves through that port during the piston strokes.
All cams stay open past BDC to allow this moving mass of intake air to continue filling the cylinder even after the piston starts moving upward during the compression stroke. Since this last minute filling is critical to maximizing your engines power output you want to maximize this filling effect and the only way to do so is to maximize the velocity of air moving through your intake and ports.
Similar forces are at work helping to get the exhaust out of the cylinder during the exhaust stroke.
The art is to balance maximizing these velocities without restricting flows and matching these flow dynamics to the cam and powerband characteristics.
Well, I hope this clears up some of the voodoo and misinformation that surrounds this subject.
INTERTIA STUFFS CYLINDERS !
Most ports are big enough to flow all the air any engine can handle. What port size changes is how fast the air moves through that port during the piston strokes.
All cams stay open past BDC to allow this moving mass of intake air to continue filling the cylinder even after the piston starts moving upward during the compression stroke. Since this last minute filling is critical to maximizing your engines power output you want to maximize this filling effect and the only way to do so is to maximize the velocity of air moving through your intake and ports.
Similar forces are at work helping to get the exhaust out of the cylinder during the exhaust stroke.
The art is to balance maximizing these velocities without restricting flows and matching these flow dynamics to the cam and powerband characteristics.
Well, I hope this clears up some of the voodoo and misinformation that surrounds this subject.
Last edited by 0HP930; May 24, 2004 at 06:58 PM.
