Flange size 1 5/8 header small or BIG?

[Felix/DFL]

Hi Folks,
I yust recived a 1 5/8  +header from Turbo thomas for my notch.
Nice piece of stainless steel, there is yust one point which cracks my head.

Will the small flange (2") work on a 2,2l
Won`t it be a big restrictor at high rpm`s and let the engine run hot?

Or will the fast travel of the exhaust gas due to a venturi effect benefit?
So what ya think, or which experiences did you make?

The flange change is no big issue so that would be no problem...

Engine (still in progress):
Stroke x bore 78,8x94; Valves 42x37; FK10; CR about 10,5-10,7; 48 IDA, should go up to 7000rpm easily

Best Greetings,
Felix

[Peter]

Hello Felix,
I have a 2276 with a small flange header as well,
i dont think the flange is too restrictive for a street car,
my engine does not run hot with the external cooler,
and you have to think: you dont drive at 7000 rpm  all day.
maybe you can get more power out of it with a big flange flat out, but then in low rpms, the power can drop
I d say, just try it and if it doesn t run hot leave it like it is

[Diederick/DVK]

i thought tobi was the exhaust man in the club, felix 
didn't he modify his header? including the flange?

[dirk zeyen]

hi felix,

walter (bug-box) has done this long time ago, he posted on the old "DFL-Forum" ask him.

dirk zeyen

[Felix/DFL]

Hi Ruff,

thank`s for the answer. Good to know that your 2276cc is not getting to hot.

Of course 7000 rpm is not the all day operating point.
But I don`t want that the D opened 044`s heads and welded mainfolds are for nothing as the exhaust is to restrictive.
I maybe go with a flange between the small and the big "hole".I will look what some "normal" cars have in use and adapt it.

As the merged section is pretty short I am afraid that a to big flange will destroy the scavening/venturi effect as I need to shorten it if I go to a biger flange...
And that`s the big advantage of the merged headers.
What I find really interesting is that most of the old & fast racers went with the small flange. Have a look in to the bible old and new testament or the pic`s of Fab/the living scanner

The A1 mufflers even have a neck just after the flange as the turbo mufflers...

Just thinking before I cut 

@ Diederick: Yes, Tobi has welded a 2.5 V Band on his header