Intake porting?

Bearmw

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I have a dilemma.

I am putting a B35 in my Bavaria. The motor has Paul Burke pistons and N21 cam and I am also going with the L-jet intake with 320i C-tubes, new 26lb injectors from FIC, and megasquirt. I am concerned about the size difference between the much smaller manifold opening and the head intake port costing too much power. I have put a B35 gasket on the L-JET stub to show the difference. Maybe it doesn't matter and I have seen differences of opinion on whether it makes sense to try and port the intake stubs to closer approximate the B35 port size and shape even going as far as adding some weld so the aluminum doesn't get too thin and filling the void near the injector with epoxy.

I understand a small mismatch going smaller to bigger isn't really an issue but this seems like a pretty big difference. Thoughts? Also, the stub casting is pretty rough as can be seen in the pic and I figured I will clean it up a little regardless. I am also concerned about losing too much air velocity if I go bigger at the very end of the stubs. I appreciate your input.
 

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HB Chris

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Since they will never match and the manifolds will get fairly thin I wouldn’t worry. I don’t remember port matching my b35 head and e12 manifolds.
 

HB Chris

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You will need to decide which exhaust manifolds to use. I kept the b30 as using the b35, although probably better, requires a b35 down pipe which will require some work to fit to the stock exhaust.
 

Bearmw

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As far as exhaust goes I will either try to make the Bavauto E28 headers I have fit or might go with B35 or home ported B34 manifolds and custom down pipes. So many choices.
 

Mot27cars

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As far as exhaust goes I will either try to make the Bavauto E28 headers I have fit or might go with B35 or home ported B34 manifolds and custom down pipes. So many choices.
I used b35 exhaust manifolds and down pipes from 88 735i. No problem and no tweaking.
 

Mot27cars

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That is why I mentioned the fitment issues, thanks.
Tho I did not use my stock exhaust after the down pipes ( I still have them and are in good condition) the new exhaust does follow the same original path under the car. I suppose an adapter would possibly been able to be used to attach the old original type exhaust system.
 

Mot27cars

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That is why I mentioned the fitment issues, thanks.
What I think I failed to mention or make clear was that I actually used the down pipes from the 735i and it’s manifolds, then new pipe afterwards.
Tom
 
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