Okay, so we've all got great ideas. Every now and then, we all think we've found something big. I'm not sure that I have, but I've got an idea and I want to see it through.

Let's say that I wanted to make a custom intake manifold for some funky carb that I've never seen been done before on a rotary. Would I be better off with a clay prototype and somehow make a mold, or just cut flanges, put them in place, and weld up pieces of tube to make a tubular manifold? Maybe there's a third option, but I can't think of it (short of JB Weld).

If I can cast a manifold but it's a lot of development, at what point would it make sense? After 5 parts? 20? Does anyone know a good DIY site for making aluminum intake manifolds?

 

Sterling did some research on this for a performance minded Nikki manifold. The cost was extremely high just for the first casting, and a lot would have to be sold just to break even. Your best bet, price and time wise is a tubular manifold. Flanges can be laser cut for a fairly decent price, and a little welding can have it together easily. Just be careful selecting the tubing size.

 

yeah tubular is the DIY way to go.

we built the PP one for mine.

 

I couldn't see the benefits of trying to cast your own intake manifold versus a tubular one unless you intended to implement something like coolant passages, or some sort of bypass valve built into the intake manifold.

The tubular manifold is probably the most simple, and having them welded up shouldn't be that hard, by the way... are you planning aluminum or steel?

 

what sort of cool carb are you thinking of using?

 

I looked into this recently, there is a good DIY casting tutorial on the web, its somewhere on google. However making one out of aluminium tube and plates would be much easier.

For a stock nikki carb all you'd need are 2 x 90° 1.5" bends, 2 x 90° 1.25" bends, and then a plate for the carby flange and another for the block flange (plus a bit of bending on the tubes) Using an aluminium brazing compound like super alloy 5 to put them together unless you can TIG weld. I am planning on doing this when I get the funds together.

 

double post

 

yes crit, tubing is the best way to create a custom intake. once u get ur final design and it's something u want to put into production, then u can look for someone to do the actual casting of the final product.

 

We learned how to do sand-casting of aluminum in high school (my high school had an awesome voc/tech department). Tool-up costs would be high for a true DIY approach, and since you're trying for hollow parts of large size, it gets fairly involved.

Weld-up would to my mind be a lot easier for low-count or experimental work. Plus you can make a lot of mods to it without having to scrap the entire part.

 

I always wondered how they made a tube into an oval without ever cutting it. I know you could
just clamp it together, but the area of the oval end is less than the other end of the pipe!

Also Crit, some things I have found helpful I usually found in the fab section:
https://www.rx7club.com/forumdisplay...c&daysprune=-1

 

Casting is just too expensive for one-off kind of deal. But it does have the benefit of allowing complex shapes... look at the factory reinforcements and "webbing" you see on a lot OEM manifolds.

 

I would assume just as they use a die to make the tubes they use an oval die?