I put together a little chart , that I had with some head flow numbers here. The EQ's have been flowed by my guy Mike at High Flow, Jim Valako, and Scott Foxwell so far. While everyones bench can certainly be different, the numbers are starting to speak for themselves. All 3 of these EQ heads, have stock ports. Those are good, real world , not "advertised" or inflated numbers.

Full Force Tim's FULLY ported AFR 325's, flowed well too as you can see.. But, again, a set of afr 325's are 2300 set bare. EQ's, 900 a set bare. EQ heads have powdered metal valve seats, the AFR's, Ductile Iron.

I'd like to see someone like Valako do a full port job on these, and see what happens. Getrdun?

Mild, Jim V # for exhaust flow at .8 was 300. Sorry didn't include that one in earlier post.

I'm certain he has fully hand ported EQ numbers. Jim will typically give a guy the best bang for the buck so to speak unless specified by who he's doing the work for. I can appreciate that as after a point you can spend hours a heads chasing just a few cfm. Not real cost effective nor performance in reality. Those are some awesome numbers as posted. ive known Jim since the old epoxy floor days back in late 80's. He simply does great work and is honest as they come. Many other good head porters and engine builders as well but I just happen to hook up with him way back and have a great relationship.

I'm curious to see where he comes in at with the promaxx. I knew he was getting pretty good numbers with the EQ's. I will start another thread with Promaxx numbers. If there's no casting flaws or issues and flow similar to EQ's that will be great. Will always be a place for darts, afrs, brodix but glad to see some others getting recognition for a couple of reasons. It might just drive some ot the others pricing down and it makes a build more affordable with same same results.

will you have numbers for the promaxx prework for a baseline?

Oh for sure. It doesn't take long and wouldn't even consider not. That's part of the pride and bragging rights. Lol.

332's. ;)

I'm not getting it? You mean the 332 Brodix?

From Chad Speier , thought I'd post it. Good info

This is probably the most asked question I get. What size head do I need?? While head CC's are a by-product of a properly sized cylinder head, there are mathematical formulas to lead you to the correct answer. There are many reasons that choosing a cylinder head based off port volume is a bad idea, simply put there are 100 ways to arrive at a port volume!

First off, CC's or port volume measurements are “close guesses” to a ports average air speed only. It gives no insight what so ever into the ports velocity profile. CC's came about in the 60's when the heads where to small so the larger the port, the more power one could make. Head porters still use CC's as a quick dirty guess as the average air speed in the port, that’s all.

With three know things about any cylinder head, we can arrive at port volumes. Knowing this along with a program such as Pipemax, we are able to choose cylinder heads in a way they that is proper and logical. It's all about average velocity in the induction, 260fps is a great starting point!

Most cylinder head porters are working off a desired MACH speed of the port. 1116 feet per second = speed of sound @STP or .55 MACH. You can design ports slower than .55 MACH, but it's usually considered the speed at which "choke" or "port limiting velocity" occurs in a running engine.

613.8 fps = .55 MACH


So let's look at the important things we must know about our cylinder head. We need to know the following in choosing the correct cylinder head:

"average" intake port length (roof length + floor length from seat ring to opening) divide by 2
port volume cc's


Then we need to look at bore and stroke and desired RPM in selecting the cylinder head. The correct formula for determining how big of cylinder head we need:

MIN CSA = (bore x bore x stroke x RPM x .00353) / 613.8 (.55 MACH x 1116 fps)


Let's build a 434 SBC turning 7000 rpm. 4.155 x 4.155 x 4.000 x 7000 x .00353 = 1706 / 613.8. The formula says you need 2.78in²²²² of MINIMUM CSA to achieve your RPM goal...

Now let's turn your MIN CSA into a CC's for choosing a balanced cylinder head. Remember from above, I said you needed to know port volume and average runner length! Now let's put those into out formula:

Port Volume CC's = MIN CSA x Port Length x 16.387


Most SBC cylinder heads are in the 5.45 port length. Again, roof length plus floor length divided by two. So 2.78 x 5.45 x 16.387 = 248 CC's... Our math is telling us to achieve 7000 rpm from a 434 cid, we need 2.77in² MIN CSA and port volume of 248cc...

The key to any cylinder head is a balanced port. We are trying to balance it around a MIN CSA to achieve proper filling. SRH designs and ports based off velocity profiles. Although formulas are nice for "ballpark" sizing, localized and average velocity is KING!


I get this question PM'd to me all the time so I though I would take some time and show you how it's really all about AVERAGE AIRSPEED in the induction.

Two totally different cylinder heads, different flow curves, different port volumes, but yet the same average airspeed.

I'm going to use my CNC heads for the examples (because I know they are correct FPS vs AREA vs CFM)

Head #1. v2.70PF.. Flows [email protected].. 250cc port.. 5.47 long
Head #2 v2.50PF.. Flows [email protected].. 227cc port.. 5.45 long
Manifold Holley 300-110 in AS_CAST form.. short runner=4.625, long runner=5.500
short runner pours 215cc.. long runner pours 240cc

FORMULAS:
Average CSA = Port Volume CC/ (Port Centerline Length * 16.387)
FPS= (Flow CFM * 2.4) / Average CSA

Head #1 flows 320cfm through manifold and carb
Head #2 flows 305cfm through manifold and carb

Head #1= 465cc short runner.. 490cc long runner
Head #2= 442cc short runner.. 467cc long runner

Head #1= 10.08 short runner.. 10.95 long runner
Head #2= 10.10 short runner.. 10.98 long runner

Head #1= 10.08 x 16.387 = 165.2 / 465cc = 2.81 avg CSA short runner
10.95 x 16.387 = 179.4 / 490cc = 2.73 avg CSA long runner

Head #2= 10.10 x 16.387 = 165.5 / 442cc= 2.67 avg CSA short runner
10.98 x 16.387 = 180 / 467cc= 2.59 avg CSA long runner

Head #1= 320 x 2.4 = 768 / 2.81 = 273 FPS AVG VELOCITY short runner
320 x 2.4 = 768 / 2.73 = 281 FPS AVG VELOCITY lon runner

Head #2= 305 x 2.4 = 732 / 2.67 = 274 FPS AVERAGE VELOCITY short runner
305 x 2.4 = 732 / 2.59 = 283 FPS AVERAGE VELOCITY long runner

NASCAR. with the rec ports and 320 runners 8k plus rpm.

Ok let's take a stock 454 / 365 mag build. With your formulas what size runner would be let's say adequate running at 4,900 rpm.

My heads are all ported and flowed now, sure do look nice for a backyard hack job... a no name idiot.

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