Portmatching exhaust/intake manifolds...questions?

[bmwman91]

I can get ahold of a second M42 intake manifold (upper & lower) as well as a second header...cheap.

I have read about portmatching the manifold to the head. How do you guys that have done this, do it? It seems like you woudl have to use paper/cardboard & some ink on the manifold to make imprints & then carefully machine away what needs to be on the manifold & maybe the head. Anyone have useful advice?

For the exhaust manifold, I hear you want it matched on the sides & top, but stepped on the bottom; have the bottom larger than the port on the head making a "step down: into the manifold. Any experience here?

Thanks!

[marakka]

I can get ahold of a second M42 intake manifold (upper & lower) as well as a second header...cheap.

I have read about portmatching the manifold to the head. How do you guys that have done this, do it? It seems like you woudl have to use paper/cardboard & some ink on the manifold to make imprints & then carefully machine away what needs to be on the manifold & maybe the head. Anyone have useful advice?

For the exhaust manifold, I hear you want it matched on the sides & top, but stepped on the bottom; have the bottom larger than the port on the head making a "step down: into the manifold. Any experience here?

Thanks!

I'm sure I'm outta my league here but couldn't you do this with the gaskets to help you along?

[bmwman91]

I though about that. My concern is the tolerance left aroung the mounting studs. Though it was a worn one I played with, it seemed that the gasket might be able to move a tiny bit on those studs. A mis-alignment of the manifold/ports would be a bad thing. Maybe if I reinforced the holes (binder paper hole reinfircements wheeeeeee) it owuld work. Good idea though, maybe I will give it a shot.

[marakka]

I though about that. My concern is the tolerance left aroung the mounting studs. Though it was a worn one I played with, it seemed that the gasket might be able to move a tiny bit on those studs. A mis-alignment of the manifold/ports would be a bad thing. Maybe if I reinforced the holes (binder paper hole reinfircements wheeeeeee) it owuld work. Good idea though, maybe I will give it a shot.

Figure you might have slight mis-tolerances on either method you try..... at least this one you can center the holes (assuming that both intake and exhaust manifolds use the same diameter mounting bolts) and go from there..... If any thing lines up like that....

[Flip_Side_the_Pint]

when you port match manifold you use the oem gasketry. You take a oem gasket and place it on the manifold. You can then do two things. Tape the gasket to the manifold and port the needed metal out. or if you plan on using that gasket fill in the metal you need to remove with a sharpy.

Thats how I did it.