Ported Dart pro 1 pre platinum

[GARY C]

Here is a good read from Darin...
"Exhaust Port Design
I have bad news. You can not design an exhaust port on a flow bench the way you do an intake port. If you’re designing exhaust ports to flow the most air possible, you’re destroying the engines ability to blow the cylinder down and exhaust properly."

He has lot on this page about heads.
http://darinmorgan.net/frank-talk-about-flow-numbers/

Another good one here.
viewtopic.php?t=691

[Carnut1]

0106171713b.jpg

Before D shaping.1 7/8" pipe

[Carnut1]

0106171720.jpg

Shot of spray paint as a guide. I am doing this in hopes or losing the turbulence. Thanks, Charlie

[Carnut1]

0106171749.jpg

More like ovalish on three sides, floor untouched.

[user-9274568]

That square exhaust port bugs the shyt out of me! lol

[Carnut1]

That square exhaust port bugs the shyt out of me! lol

I am not really a fan of square either!

[user-9274568]

That square exhaust port bugs the shyt out of me! lol

I am not really a fan of square either!

I did my CNC port much like where your going with yours.

[GARY C]

I could be wrong or it may be the picture but Carnuts short turn looks to narrow wall to wall.

[MadBill]

Has any factory head had more exhaust port shape changes than the BBC? Square, round, 'D', 'C', squared 'C'...

[GARY C]

Has any factory head had more exhaust port shape changes than the BBC? Square, round, 'D', 'C', squared 'C'...

I tend to favor more of the D shape to slow the floor down but I am not a head porter...but I do own a die grinder and I have stayed at a Holiday Inn.

[Carnut1]

Turbulence is still there but a bit less. 1.9cfm improvement @.3" lift to a full 10 cfm@.8 "!
231.5 cfm@ .8" no pipe. The speed across the floor is slow so widening the ssr may help the turbulence. Thanks, Charlie

[user-9274568]

Here is a better pic at how wide the floor is.

[user-9274568]

Here is my Super Stock exhaust port. Trying to show you W I D E floors!

[Carnut1]

Here is my Super Stock exhaust port. Trying to show you W I D E floors!

That is sweet Chad. Looks brazed? I will ask because I am sure you know. When the port is in bad turbulence the Pitot shows 0ft/sec dead center of floor outlet. Wider floor would drop airspeed even more possibly making it more turbulent. Or make it over more of a lift range. There is a question in there

[zums]

Developing an EX. port on the flow bench,... how do we decide what works best for power, like the following ??

I was doing some EX port flow testing this morning ( since it's below zero here this morning and it's 70* in the shop ) and I had a 80cc port that flowz 235 cfm through a 1.55" valve with a 1.35" throat. I then added 5cc of clay on the floor starting at just past the throat and expanded the thickness as it went out to the header flange. So the floor was a little higher when done with the clay. The 75 cc port flowed 225 cfm.

The average speed at 235cfm and 80cc would be a little slower than 225cfm at 75 cc, but since the throat stayed the same size, average throat speed ( DC ) would be higher with the larger port. The CSA from throat to port exit would change less with the smaller ex port.

Both keep the manometer stable, but the smaller port was a little quieter.

Which port will make the most power ?

Do flowZ rule and making the 80cc port 90cc for a 5 cfm gain would make more power?

I have my opinion, but want to see what others say, since this thread moved to EX. ports.

Hope Carnut don't mind ??

Randy

My question is, how the hell did you get the clay to stick, everytime i clay the exhaust it melts and winds up on the wall 3 feet to my left
Tom