Anyone with a bisimoto header that's not installed...

[theSOB]

Quick question, can someone please tell me what the flange size is so i can match my head to it when i port the exhaust size. Or is this a custom size that Bisi asks for?

[19dabeast85]

Quick question, can someone please tell me what the flange size is so i can match my head to it when i port the exhaust size. Or is this a custom size that Bisi asks for?

I'm sure bisi uses a standard flange for any of the 190-220 whp custom headers he makes. I'll measure mine tonight when I get home if nobody else posts up.

Make sure you don't make the ports the exact same size as the flange....they need to be a bit smaller....there's an exact science to this that I don't know off the top of my head. You'll also not want to make the ports larger than the openings in the stock exhaust gasket (IMO). I believe the exhaust gasket profile would make a great starting point for porting.

[19dabeast85]

49.5mm X 37.0mm

[theSOB]

thanks, i'm gunna go take some measurements and see how they compare

Stock (f22a1) in mm:
Header 31.2 X 45
Aftermarket header 31.2 X 42
Gasket 35 X 48
Head 30 X 45

[19dabeast85]

If my information is correct the ports don't really need to be made much larger, only a tiny bit. The flow gains are made by optimizing the shape of the port "necks", something I'm going to let CHR or Bisi do for me.

[theSOB]

hmm, i'll do some more research. i just wanna walk into the machine shop with as much information to the guy as i can get

[D1sclaimer]

hmm, i'll do some more research. i just wanna walk into the machine shop with as much information to the guy as i can get

Which machine shop?

[theSOB]

Which machine shop?

probably jut bring it down to Rojam. close and convenient

[GhostAccord]

Do some research into the exhaust port anti reversion step. I think that is what beast is referring to when talking about the port opening being smaller than the flange opening.