General Cylinder Head Flow Numbers discussion

[HawkBrosMav]

Originally Posted by SSDiv6

You need to take into consideration the intake manifold and throttle body flow also. No matter how much air flow you have on the cylinder heads, the intake manifold and throttle body/carburetor, can become a restriction.

I get that, but would you run a set of heads you knew flowed less air intentionally knowing the TB and intake may be a restriction larger than the heads or would you put the "best" flowing heads on regardless?

I think I'm more curious as to what people are more concerned with if area under the curve is similar between 2 sets of heads. Having the larger peak numbers or giving up a little up top to have much better down low numbers. Obviously there are other factors to consider... mainly possible restrictions before the port and then the relation to exhaust port flow as mentioned in the next reply. But at this point for a simplistic questions and answer.. would you prefer a head that peak flows more or flows down low more given the overall "area under the flow curve" is generally equal.

Billy seems to lean towards low flow potentially with his response.

[SSDiv6]

Originally Posted by HawkBrosMav

I get that, but would you run a set of heads you knew flowed less air intentionally knowing the TB and intake may be a restriction larger than the heads or would you put the "best" flowing heads on regardless?

I think I'm more curious as to what people are more concerned with if area under the curve is similar between 2 sets of heads. Having the larger peak numbers or giving up a little up top to have much better down low numbers. Obviously there are other factors to consider... mainly possible restrictions before the port and then the relation to exhaust port flow as mentioned in the next reply. But at this point for a simplistic questions and answer.. would you prefer a head that peak flows more or flows down low more given the overall "area under the flow curve" is generally equal.

Billy seems to lean towards low flow potentially with his response.

I always flow the intake manifold first and pick the best. Many years ago I flowed lots of Ford 5.0 intakes and the biggest variation was the lower manifold. As I recall, there are 4 different lowers from different foundries with the same part number and the difference was the last revision letter on the casting number. I believe I flowed around 22 lower intakes and picked the best 4 and the remainder I took to the aluminum recycler.

Having the baseline number from the intake allowed me to then work on the heads, knowing the Delta the intake would effect on the cylinder heads. The brand of valves makes a difference the same as the cut and angles.