This has me a bit confused, so I thought I would ask someone who knows. If you have a 454, let's say it close to stock, except for the Cam. For this example, lets say the cam is close to a 224/230 Int/Exh Duration @ .050. The Int lift is .515 and Exh is .520. This should allow you to get to around 5800 rpm (with the right springs, etc). Now the catch, you only have a set of 781 stock oval port heads. These heads will flow 265 cu ft on the intake (@ .500 inch lift), according to the chart that I have. I have seen a flow test done on these heads, which showed a bit higher value than the one listed above. If I understand what I am doing, one cylinder of a 454 is .033 cu ft. Therefore, .033 times 5.8K is 191.4 cubic feet. I have plenty of room to play with, I never come close to the limit of what the head can flow. The question, what is the advantage of going to an aftermarket head? How would an after market head add any power to this setup (keeping the compression the same between heads)?

Thanks,
Fred.

It is because the head port doesn't flow smoothly and contnuously, like your calculation assumes; it flows only for a fraction of the total time, in little pulses.

For example, if your one cyl requries 191.4 CFM long-term, and it's flowing one quarter of the time, that means that the flow rate WHILE IT'S FLOWING must be FOUR TIMES that 191.4 to deliver that much air.

Of course it's not really that simple, since flow numbers assume a specific pressure drop in the port, which may or may not apply to your particular motor; but the principle still applies.

It's the same reason why you typically need a larger carb than the raw "CFM" calculation would indicate, especially on a dual plane intake with a very small plenum (no smoothing or averaging of the pulses).

If you wanted to lok at flow vs cylinder volume,the best area to examine is flow at .300 lift. But for practical purposes. I would be inclined to expect peek power of a 454 oval port motor with a 224@.050 intake to be around 5300.

Ok, that helps a lot, but this brings up another question.

Quoted from RB69SS396Conv:
"For example, if your one cyl requries 191.4 CFM long-term, and it's flowing one quarter of the time, that means that the flow rate WHILE IT'S FLOWING must be FOUR TIMES that 191.4 to deliver that much air."

The above has me still a bit confused, but the rest makes perfect sense.
On the above statement, I would expect it to flow half the time, every other revolution. So, the above example would imply that it really needs twice the 191.4, at the upper RPM's.
Where I would guess the quick draw of the piston needs a larger port to easily take in the air it needs, and being smooth and larger helps this. Hence the need for the larger aftermarket heads. It's makes a lot more sense now, as you can see where the extra 40 hp, etc comes from, with atermarket heads.

Thanks,
Fred.

Fred,
You also need time to compress the mixture, time to make power & for the exhaust to do it's thing ;)

Intake
Compression
Power
Exhaust

Thanks Mike,

Life is tough for me, and even tougher cause.....

Ok, now I see where the 1/4 (or four times) comes in, plain as day. Even the high flow heads don't flow four times as much as good flowing stocks. So, this being tied into the volume-metric effeciency of the engine, is all part of the attaining more HP solution. So, High flow heads are just a big step up, but you still have the problem of starting the flow in a short period of time, and the turbulence factor, which better heads help with. So with the right carb, heads, and perfect cynlinders /rings /vacuum / Cam, etc, you can attain the best a normally asp engine can do. Which is a bit of a surprise that it can attain more HP per cubic inch. Ok, that all makes sense now. Now I just need to sit down and tie it all together.

Thanks,
Fred.

Don't forget about velocity.

Could anyone suggest a good book that ties the head flow, cam variables, flow, velocity, accelation of the mixture, etc all together?

Thanks,
Fred.

It good that you want to learn, but i say who cares lol. the stock heads are all you need. on the cam. I had a lot more cam and it ran out of power at 5800 in my 454. But it ran low 11s.