cast iron exhaust manifold porting

[quikup]

I'm in the process of replacing the turbo and thought I'd clean up the exhaust while I was at it. The main question concerns the casting lumps internally adjacent the lower manifold bolt holes. It looks to me like removing those would leave the manifold thin in that area creating a hot spot. Any other guidence on increasing the flow would be appreciated. The manifold in question is an '86 SVO. I've done the obvious stuff.

[MikeFleming]

Remove them. I've never seen a problem with smoothing out that area. All of my E6 manifolds have those bosses removed.

Someday I'll get some pics but that area just doesn't photo well.

[quikup]

Thanks Mike, I had kind of already smoothed off the tops and blended but now I'll go whole hog. Cheers.

[86svo9l]

Same here, ground them out. Also when I did mine I opened the outlet up to match the gasket instead of the sideways D shape and contoured and removed material to unrestrict the #4 and #3 ports. If you feel inside of there you will feel a sharp edge coming from those areas and it can help to at a minimum radius and blend that area in to improve flow.