I have a S&P MPFI unit and I took it off last night(for other resons) and noticed the ports aren't very smooth and have casting lines. So I was planning on polishing this out, But I was just reading here that someone said they should be rough so the fuel will float? That don't make sense to me but I'm just starting the port and polishing thing. My question is should I smooth out the complete ports?

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92 RS, 350, Street & Performance MPFI, TFS heads, Stock crank and rods, Fordged flat tops,
Crane Rollers,
MSD Digital 6 Plus, 22lb injectors,
ZZ3 cam, Edelbrock Headers 1 5/8, 3" Exhaust,
Hi Flow 3" Cat, stock T-5,
stock rear 3.08, koni yellow adjustable front, twin turbo glass hood, T-tops, Auto Meter Ultra Lite Series 2 5/8 gauges, Teal Green

 

92,

If you have a dry intake (as in a TPI or any port injection system) you can polish the intake runners. With a carburetor or central TBI or DFI system, the runners should not be smooth. Fuel droplets in the intake stream will cling to the smooth runners and wet down the walls rather than stay in suspension and reach the chambers.

Polishing the runners of a dry intake may provide a minimal increase, or none. The gain may not be worth the effort unless you are at the 800HP level and would like to get maybe 3HP more. It is probably far more important to match the runner openings to the heads than polish the runners.

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Later,
Vader
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Justice and Freedom will Prevail