I finally got around to checking the actual port sizes on my Big Block AFR 335cc CNC heads, just as they came out of the box. They will be going on the 540 I'm building. So, I cc'd # 1 intake port and # 3 intake port. Here are the results:

# 1 intake port = 330.5cc which was confirmed by a repeat measurement

# 3 intake port = 335cc which is of course right on the money

Additional comments:

# 1 and # 5 intake ports are the same geometry

# 3 and # 7 intake ports are the same geometry

Ports 1 and 5 have to reach .500 further in the front/back direction than do ports 3 and 7

Ports 1 and 5 are longer, yet are smaller in volume, and they flow toward the center of the cylinder

Ports 3 and 7 are shorter, but have a larger volume, and flow toward the cylinder wall

They are what they are, so I'll see how they work out.

There must be a method to such madness.Hope there is. Got a set on my 540.

Well that's pretty dead on it looks to me! Thanks for checking them. Lots of heads end up with actual CC's a lot different than advertised and I was curious how the AFR's stacked up. Just proves once again they are a heck of an out of the box head to make the power they do with a port that size!!

I wonder what the cross section is in them? Feel like doing a little more measuring???


JIM

Well that's pretty dead on it looks to me! Thanks for checking them. Lots of heads end up with actual CC's a lot different than advertised and I was curious how the AFR's stacked up. Just proves once again they are a heck of an out of the box head to make the power they do with a port that size!!

I wonder what the cross section is in them? Feel like doing a little more measuring???


JIM

Here ya go. I measured 4 places, in both the longer yet smaller volume intake port # 1, and in the shorter but larger volume intake port # 3. This was all done in order to get a better feel for what is going on in the ports. Dyno and track testing, tells us they make good power, so I guess we'd have to say that Tony Mamo must have known what he was doing. Check it out:


1. At the intake gasket surface -

Both intake ports # 1 and # 3, were 2.450" tall and 1.700" wide, which = 4.165 sq in, though it is only really theoretical, since it does not subract for the rounded corners. If you subtract .1114 sq in for the rounded corners, you get 4.050 sq in, true CSA.


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2. Down the port .750" in from the intake gasket, where the port curves in to clear the pushrod -

For port # 1, the measurements are 2.325" tall and 1.550" wide, which = 3.604 sq in theoretical. Then subtracting for the rounded corners, you get 3.493 sq in, true CSA.

For port # 3, the measurements are 2.325" tall and 1.650" wide, which = 3.836 sq in theoretical. So subtracting for the rounded corners, you get 3.725 sq in, true CSA.

If you average the theoretical CSA's, you get 3.720 sq in. And if you average the true area's you get 3.609 sq in.


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3. Down the port at the head bolt location -

Both intake ports # 1 and # 3, were 1.935" tall and 1.885" wide, which = 3.650 sq in, though it is only really theoretical, since it does not subract for the rounded corners. If you subtract .1114 sq in for the rounded corners, you get 3.539 sq in, true CSA.


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4. At the intake valve seat ID -

Both intake port, valve seat ID's are of course the same. The ID = 2.085", which = 3.414 sq in, true CSA.


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In summary, if you look at the changing area's:


For theoretical - it goes from 4.165…..to……..3.720…..…to……..3.650………to……3.414 at the seat.

For true area - it goes from 4.050…..to……..3.609…..…to……..3.539………to……3.414 at the seat.


So, you can see that the port progressively reduces in CSA from the intake gasket, all the way to the valve seat. This leaves the valve seat ID with the minimum cross sectional area (MCSA).