What is the port size difference between 318 and 340-360 heads

[MileHighDart]

So I've been reading tons of threads lately about engine building, and different combos and such. Keep hearing the intakes like the Eddy-performer have smaller "318 sized" ports.

What exactly are the measurements of intake ports on a 318 head vs a 340/360 head? Or how much difference is there?

Several of the intakes I'm looking at say their ports are 1.96"x1.00", but they say they are for 318-340-and 360, so just wonder how this corresponds to the actual intake ports on the heads

 

[RustyRatRod]

Fel Pro lists two main intake gasket port sizes. 2.08 x 1.05 and 2.27 x 1.16.

 

[Locomotion]

Having a smaller intake manifold port than the cylinder head port is usually better. A bigger intake size can create a minor "dam" effect and cause turbulence, which may negate some or all of the advantage of a bigger intake manifold. So the "small" port Edelbrock Performer fits & works fine on 318, 340 or 360 heads. The Performer RPM has bigger ports and would be more "productive" than a regulat Performer on the 340/360 heads.

Gaskets are usually a hair bigger than necessary to avoid sticking out into the airflow.

I don't have the actual sizes, but there may be very minor differences, as well as core shift.

 

[Marcohotrod]

simple rule, use the small port like performer intakes on the 273-318, and the larger port intakes like LD340, performer rpm, victor on 340-360