Hey guys sorry to revisit a subject that I'm sure has been visited.
I just cant find any descent information I'm looking to open up the ports where the butterflies are on the BBM as they look quite small when compared to the ports at the end. Then possibly give the manifold a Polish and clean up on the short runner. To do this I will need to fit larger butterflies as they will no longer be big enough to cover the holes when closed. I have no intention of removing the BBM function as I want low end torque to remain. Has anyone done this before main problem is I dont know where I would get larger butterflies to replace the existing ones....

It to me looks like this could yield a good 5-8kw on a modified engine or am I all wrong on this..

Thanks in advance fellas.



Looks like a good 2-3mm smaller at the butterflies. Surely a restriction. Air also would not flow on the long runners once the butterflies are opened either.

The butterflies if memory serves me correctly are made of brass you could make your own but it wont be cheap and easy.

I have thought of this too.
Have been told it isn't worth the effort.
Still keen to find out more.

Hey man just compared the butterflies to the port. About the same. Looks are deceiving but where the entry to the butterflies are is quite rough. Will do a clean up there and knife edge the butterflies.

Also thinking of getting a BA throttle body and gutting the servo motor off it and retrofitting the EL rod and cable connections to the side of it and use the BA butterfly. If I can get that to work it will be a $20 70mm throttle body lol doesn't look impossible but probably a pain in the butt.

Wagondad did a fair amount of porting with his heads being flowtested, did BBM's as well, see his gallery: http://s860.photobucket.com/user/johnha ... t=3&page=1
Good doco on TB's : fordmods-technical-documents-diy-f38/improving-your-6cyl-e-series-throttlebody-the-diy-way-t84040.html

Thanks for the links snap. Def some good stuff there!

I have seen a process, where grinding paste is forced through manifolds, to smooth out all the lumps and bumps. Especially done in production racing classes.

Extrude Honing