Porting Intake BBM.

[Petrie]

As said above,

Is it better to do with a flow bench?
As I'm keen to give it a crack by hand but if it's better to be machined in shop then so be it.


The butterflies mid manifold. Have had so many different opinions on removing/keeping them,

Being worked n/a- would it be worth leaving them in with bigger butterflies? As I can see the engine losing low down torque without the butterflies.

[turbo_will]

Keep the butterflys great bottom end power with them left in. Spend some time cleaning up inside with a die grinder and see how you go.

[Petrie]

Keep the butterflys great bottom end power with them left in. Spend some time cleaning up inside with a die grinder and see how you go.

I'll give it a crack this weekend with a carbide burr. See what happens.

[kwikxr]

Fairly worked NA with the BBM, I'd leave the butterflies in. The factory setup works great for producing torque down low, so eliminating the butterflies in the BBM would result in some pretty average performance down low.

Unhook the vacuum hose from the BBM switchover diaphragm in front of the BBM and see how it drives with the butterflies open all the time. I know this is flawed since the ECU isn't exactly tuned for this condition, but it'll give you an idea of how doughy it could feel without the butterflies in effect, it feels slow as shit.

Right below the butterflies on the lower half there is a usually a big step where the machined bores transition to the casting, you can blend this so it'll flow a bit nicer. Other than that, try to port match the upper to the lower half (mine was quite a bit out so it was the first thing I did) and just do a general tidy up of casting dags.

[Petrie]

I'll take your word for it mate!

That step underneath the split section would be the first thing to go for sure.
I'll have a sus out this weekend. Should just be able to knock the pin through on the butterflies? I haven't looked at it yet.

[kwikxr]

You'll need to remove each of the butterflies from the shaft first (2 screws for each one), then undo the 2x 10mm bolts holding the vacuum diaphragm to the BBM and the shaft will slide out with it in one piece

[Petrie]

You'll need to remove each of the butterflies from the shaft first (2 screws for each one), then undo the 2x 10mm bolts holding the vacuum diaphragm to the BBM and the shaft will slide out with it in one piece

Far easier then what I thought! Laaaarves it!

Thanks buddy.