Instead of having them weld a flange to the cast mani, can I just machine the bottom flat, and drill/tap it for the wastegate, so the wastegate sits directly against the manifold? I'm sure there's something wrong with this idea, so please enlighten me.

I don't like the idea of welding cast.

(None of this)

 

Its pretty thick in that area, I don't see why not. Might not get enough exhaust flow/pressure in the manifold to force enough gasses through it though.

 

It's not thick enough, sorry.... You could weld on a flange as long as the WG would not hit the manifold. Welding the cast manifold is not a problem - as long as it is done correctly!!
Stephanie

 

Welding cast is just fine. If you can source a older FM/Begi manifold you can drill and tap those.

Take a look at PatsMX5 manifold build: ZING! Welded properly and it will be just fine.

Also if you are looking to maybe switch your manifold, there is the HKS. Check out Gianic: ZING!


Older Begi/FM manifolds had thick areas that you could drill and tap: My FM3 is beefy as hell and works like a charm.

 

seen it done on a HKS mani too.

 

that manifold looks like it was designed to flow!

just build a tubular manifold... if your serious enough to get an external gate spent the $ to get a real manifold.

 

Hey hey, no need to bash my antique Shiiit, I am the fourth or fifth owner of that fine beauty. Probably over 200K on that thing and I still make full boost before you start building Just messing man, that picture was taken before I cleaned it, painted it and ported the whole thing with a dremel. It does look ugly as hell though, lol.

If the OP already has the manifold then there is no need to spend alot of cash on a new manifold and downpipe. It will be be cheaper and easier to just modify the one you already have. Plus the benefit of having a cast manifold on a daily driver. These things are built like tanks and will probably outlive the car.

 

just chirpin.

but a quality manifold will last just as long as a cast manifold.