Why is ther no formula to figure out port volume?

On the "funnel effect"-
While I agree this is the result, I don't believe the funnel should go to the valve. As I understand it should be the entry of the short side radius. Then problem I see with this approach is the pushrod area is the smallest cross sectional area in a factory head port. With every mopar wedge head this is the case. So the funnel simply cant be maintained without some serious working unless you go from pushrod pinch to short side entry... Which makes the funnel only a segment of the head's section of the port, rather than the entire port. This get's back into the larger/smaller/larger issues with speed thru the entire length. Honestly, I do not typically cc a port, my heads get flowed after the work's done, and not every set gets tested. So in truth, it's hard for me to say the funnel approach isnt all that critical with no backup numbers. However this is one area I take a different approach than BJR, and it's worked for me. I tend to keep my inlet size at gasket size, and I don't enlarge the pinch more than I have to to keep it from being the restriction. I concentrate on the port sides, short turn, and the venturi to the seat, and do very little to minimize the guide boss. Overall, the port remains a very small, and the volume around the bowl is the largest. This is so the air can make the turn to the seat with little tubulence, and the venturi above the seat speeds it up into the chamber. I also tend towards larger intake valves, but not for flow reasons. I normally run 1.88s in the 318 port heads, and 2.05s on everything else and I don't see losses in low end. I run larger valves because on 40 year old seats, I will lose more power by sinking seats and enlarging chambers than by any loss of low lift flow. I'm buying valves anyway, so I place the seat angle right on the edge of the chamber, and the top cut is an unshrouding cut of the chamber itself. (5 angle valve job...)


On the rpm limits of them - Again, simply pointing out a difference of opinon based on my limited experience... No 318 port head I've ever seen or run, when on a running engine of larger than 318cu inch and paired with a street type cam, pulls past 5500. The cars heal over when they pass it. I've also never flow tested a set I ported...lol. And by running a larger cam (larger than the typical 268 style cams) perhaps that might be different. So it may be a simple deal of not enough air available. It might just be me. But I don't reccommend them for a build beyond 318 inches unless the rpm limit was 4K rpm. I'd rather run the Magnum designs with the better chamber and better all around flow in stock form then spend dollars modifying the small ports.

BJR said "Also too when flowing a cylinder head you really should have the intake manifold that is going to be used also attached to the head so the flow and or modifications can be made in real world circumstances. The only other effect that will be but cannot be accounted for is varying air pressures and changing corrected altitude's (Baro readings), and density. Which this has a direct effect on how the heads and air moves through the engine and it's ability to perform properly. This will also change the wave or pulse of the port/intake, thus the need for leaning or richening the carb, or fuel system."

I agree 100% on the above. However, on teh intake deal, in order to compare numbers with everyone else you need to be all using the same methods., nobody else does it....lol. Or at least publishes results. Hughes started flowing manifolds alone, and claiming huge increases in flow with porting. I think this is akin to gaging water flow thru a dam by watching the level drop on the shore when a gate's openned. You know there's more going out, but you can't accurately tell how much. There's so much more at work in a running engine, that simplifying the intake flow to X cfm is rediculous. Ona race engine, you can science it out. For the vast majority of users, the simple plenum size and runner volume/length is all you need. A related note, it is seldom mentioned, but flowbench packages (which includes the operator) are never going to be 100% exactly the same in results. There are calculations and formulas to even the filed. But even things like the test bore size can make a huge difference. Flow a set of Edelbrock RPMs on a 4.35 test bore, then flow one on a 4.5". Then take it to a shop close by, abnd have the same thing done. You'll end up with 4 seperate numbers. One number will be largest, one below average, and the head never changed...lol.

PS - I still cant get the color thingy going... sorry for the black and white.