D port or round flange design for headers?

[Jake]

What would you guys recommend for header flange design with a D port exhaust design. Should I buy the D port flanges or go with the round ones like I am thinking? I am gonna build some turbo headers for my L92 heads.
Thanks.

[68Bird]

You sure you know what your doing?

Round port will be easier to work with and I don't think it'll matter for a turbo header, just as long as the flange doesn't cover the port. I also can't say I've seen any d-port flanges for sale even.

I'm getting turbo envy.........

Craig

[mrtbolt64]

What would you guys recommend for header flange design with a D port exhaust design. Should I buy the D port flanges or go with the round ones like I am thinking? I am gonna build some turbo headers for my L92 heads.
Thanks.



I did the same thing a few years back when I was getting custom headers done. I put forth all this work to make sure my flange matched the exhaust port configuration then took them to the guy the was making my headers and his statement was.


Nice.............. now go make them round.

[Jake]

You sure you know what your doing?

Round port will be easier to work with and I don't think it'll matter for a turbo header, just as long as the flange doesn't cover the port. I also can't say I've seen any d-port flanges for sale even.

I'm getting turbo envy.........

Craig

Nope ;)
I'm down with the round hole, it seems natural. :D
SPD sells both flanges. For now the engine may be N/A till I get everything rounded together for the 101 I've got coming. :D My plan is to build a set of downswept turbo headers that I can aim backwards as shorties for now then flip around when I do the turbo.

[DERTY]

We use round ports on everything for turbo headers. Having a port match is good for not generating any back pressure in the exhaust. Fortunately turbo headers work based on the notion of back pressure. Just make sure you're not running a port that covers the head and it should be fine. If you want to increase your backpressure while still using a large port, consider a reverse stepped header where it starts large and then drops down a size a few inches after the flange.

[Jake]

Thanks Derty! The exhaust port sure is small on the L92 heads. I have no idea what they'll end up like after everything gets ported though. I figured on building a set of 1 7/8" headers for the 101. Maybe a little on the big side some would feel.

[DERTY]

Depends on the length of the primaries and then the diameter of your cross over pipes from the merge collector. You're main issue to look at is the volume of your headers and cross overs compared to the displacement of your motor. Smaller motors in the ~380 or less range would like a little less volume (depends on your total package quite a bit). Too much volume in your pipes and you'll get turbo lag. Too little and you get more backpressure than would be ideal. You'll have to sort that out.

[Jake]

Thanks for that insight! I could lay out what I've got here and ask for more advice on sizing for my application but could just call if you prefered that instead. I'd like to get my flanges ordered and start collecting tubing so I can play with it in my spare time.
Thanks Derty!