Does anyone know the minimum cross-section area of the intake ports on the Chapman Stage VI heads? I'm looking at both the 260cc and 285cc (max wedge) versions, but I'm not sure which will better suit my goals. I'm in the planning stages of a 512 that I want to make peak power around 6500. If the 260 port has sufficient area to not be a restriction at that RPM, then I'll run the smaller port to keep velocity high.

I have a set of 285's on my 517, with 12:1 comprssion there's plenty of port velocity (very broad torque all over even with a big roller cam). I didn't measure the port x section all the way through but I saw no pinchpoints and the tall roof combined with a short turn is one of the nicest I've seen on any Mopar BB wedge.

The Chapmans are noted for being the most efficient of the MW heads (i.e., cfm per CC of port....380cfm is typically reserved for heads in the 325+ cc volume range but also you need to factor in that head (Like the indy) have the B/RB 'spacer' factored into the casting, tough to do a true Apples to Apples.....all I can say is the flow is outstanding

Peak HP at 6500 means peak torque around 5000 rpm. For a 512 motor that means you need a CSA of 3.65 sq inches which is exactly what a MW port gives you. Any Indy head such as the 440-1, SR or EZ head that is ported to the MW size should put your torque peak right around 5000 rpm.

The Chapmans will do the trick also if you can afford the steep price tag. The Chapman heads are probably the very best BB Mopar head available in terms of airflow efficiency but most people don't care too much about that unless they are competing under certain rules.

Thank you gentlemen. I have an opportunity to buy a set of Chapmans for about what a set of CNC'd Indy heads would run me; I just wanted to make sure that I grab the right ones. I like their exhaust flow compared to the Indy's and Victor's, it means I can be slightly less aggressive when selecting an exhaust lobe.

how does chapman get those heads to flow so well....

the port on an indy head is longer making it hold about 40-45 cc's more than std,, putting your 285cc chapman heads at about a 325-330 indy head.


jeff

Jeff, yeah that's what I was saying.


Actually the increase of cc's (compared to an Indy) calculates to ~28CC's apples to apples
based on area (~1/2" width per side x 2.6 x 1.3)^16.387 = 27.7cc + 285 = 312.7....roughly the size of the Indy-1 which is around 310 IIRC

The mid-lifts are what owns on the chapmans....286 @.400 and 362 by only .600 means if you want easy 700hp potential even a mild lift easy on the springs street roller can get it done. Plus they also have a killer exhaust port compared to the VICs and EZ's. If you want stock block cracking power go up to .700 to tap another 20cfm and go for an all out racing powerband.

On 512 inches go with the 285's....worth it for the bigger 2.25 valve alone on the big stroke motors.

If you can get them at a good price they're tough to beat.

With 512" and any sort of decent compression you won't have to worry about throttle response

Look real close at them.

yeah,, i was thinking it was 3/4 inch longer, maybe i had the victor head in my mind or something,, i make a max wedge 2.700x1.400 so like you said about 30 cc's

i just did another set of 440-1 heads using a 2.250 valve on a 4.380 bore using indy's cnc casting which has a very small port in it so you can do what you want, at .400 they flowed 292, at .600 they flowed 359, 375 at .700 and 381 at .800.. the exh flowed 211 at .400, 242 at .500, 263 at .600, 279 at .700, 291 at .800,, 311 with a tube on it at .800.


im sure the chapman head has a little better throttle response, the port is raised up some if i remember right,, having to use a rb manifold on a b engine,, at 2500rpm it might have better throttle response but up at 4000 or so im sure it doesnt matter too much compared to an indy head, once you put a 4.15 or bigger stroke in it. ill bet that you build two engines comparably and the difference in torque curves wont be more than a few % different from the chapman to the indy.

with chrysler stroker motors the base thought of having a 200 cc intake runner like a stock head goes out the window. a 300 cc port is not huge for a 4.15 or 4.25 stroke,, for drag racing,, not pulling out tree stumps

So what's the answer to the original question? Anyone know the CSA of the 260cc or 285cc chapmans?

High velocity is not what you're looking for, it's the right velocity at the RPM that you want to make power at that's key...

Brad,

It was really no big deal.

Wound up using 1pc Race W-2 style 'Billet block' type pedestals and used the 1.6 Hughes Victor intake rockers....took a bit of relieving around the intake port walls to clear the pushrods for my low deck roller cam combo....for a flat tappet RB it would probably cleared without any real work. Rocker geometry worked out really nice.

But the really astounding thing about the 285's is the Chapman CNC work, the beautiful (uniform throughout) port shape and the Flawless Zeus Castings themselves....head and shoulders over anything mopar ever produced before.

What is the price of the Chapmans