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So I was looking through Stan weis’s flow page and for stock 429 heads shows “ok” flow and ported shows 305/175…
This got me thinking, when I’m using specs for my desktop dyno, the 315/180 quoted in the 460 hp chart makes lots of power, but how close is that to a regular guys porting??

I guess my question is, how hard is it to get 300cfm from an intake?? Anybody can clean up a port for that or is it “top end porters” can only do that?
Jim,

Average Joe six pack can get 290 300 / 160+ pretty easy which helps significantly if he simply follows our online instructions

Budget ported stuff is typically 305 to 315 / 180 ish. Only because I can do it in my sleep.

Large valve highly developed stuff (I don't do it any longer) will go 345+ /195 to 200 w pipe.

Work with in 1.5" of the valve offers the most bang for the buck.

Gasket matching and port matching while ignoring the aforementioned is as useless as tits on a boar.

If you look at the port exit size on a performer intake, for example, and compare it to the actual cross section about .375" into a passenger car casting they are pretty damned close.

I am still baffled by the number of folks that only address the exhaust port leaving 20+ hp on the table.

Finally:

With a simple performance valve job, properly sized choke via serdi cutters and knocking down the sharp edges...
Early castings will easily support 415 to 420 hp with reasonable cam timing. D3's a tic less due to smaller exhaust port cross sectional area at the short turn.

What it boils down to is how much work is necessary for the power I am building and the intended use???

Our budget ported small chamber stuff is making 515 to 525 hp with modest cam timing similar to the RPM package by Eddy or the same cam in non modded SCJs.




Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
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Wow…..
I gotta get out to the garage and check the porting I did many years ago to the c9 heads. Definitely not as pretty, I might have hogged out too much. I’ll get some pictures too.
Thanks again Steve.

Edit: Just thought too, I was going to run stock size valves but would just 1.75 on the exh be worth it? I’m guessing yes.
2.06/1.75 has a nice ring to it😁
An OEM size exhaust valve will flow near 180 cfm with pipe. More than adequate for 400 hp with an IE split of 12 to 14*.

When using a larger exhaust valve the choke, cross section at the short turn and through to the exit need to grow to utilize the additional valve area.
This is the point where port volume and cross section are more important than velocity. Say at 650 to 800 hp. I am done with that type of class racing port work.

After 25+ years of snorting iron dust...
Pretty doesn't make power. Air flow at the correct velocity however does.

You get to a point with the passenger car heads that proper seat, choke and Short turn shapes get you good flow say 315 cfm with a 2.11" intake valve while increasing low lift and average flow. At this point chasing higher peak numbers hurts low and mid lift offering lower average flow.

A larger valve, larger choke at 91% or so, more cross section in needed areas to slow the column as it transitions to the bowl will allow greater total flow and peak numbers. Again getting to aggressive at the short turn radii will offer greater peak numbers but starts to kill low and mid lift killing average flow.

Average flow makes power.

I've always flowed the heads with the intake of choice bolted on. Different intakes require slightly different shaping at the intake runner entry. Especially so with #4 and #5 ports.









Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
 

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10,065 Posts
The oem exhaust port does NOT FLOW 180 cfm. It can flow near that with port work with the OEM valve size.

We get 135 ish on our bench with an untouched oem style port and valve job.
I've outlined on our porting site what each mod offers for flow.

Use an appropriate dual pattern cam.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
 
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