A while ago, I noticed that certain BMW's not only have a slant six, but they have a fuel injected intake manifold that has a removable upper plenum. Today I went to the junkyard and grabbed an intake plenum off a mid-'80s BMW 528. I plan to make a runner set to adapt this plenum to my slant six.

However, I'm not sure how I will make this. I figure my options are to either cast it from aluminum, or weld it from steel tubing and plate. It may take longer to make one out of cast aluminum, but it'll look more finished and if I cast them I will be able to make duplicates should anyone else be interested in a specialized EFI manifold for a slant six. So, any thoughts on casting vs weldments? Anyone else likely to be interested in buying a casting?

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

i'd be interested in buying one, depending on price.

I think in the long run if the interest is there, casting is the way to go, and Doug (doc) would be the man in this topic

Justin

Can you take a picture of this plenum, or give us more info? I'm assuming it is a multiport injection style and the plenum your refering to is just a single (or set of) throttle plate(s)? (throttle body minus the injectors)

Sounds like a cool project but I think it is more work then its worth it... you can easily rig up a currently availible manifold with injector bungs, lets take the clifford/offy 4 barrel unit for example, then buy a currently availible plate to adapt a gm throtlte body to it. The only modifications you would have to do is drill 4 holes into the plate to match the clifford pattern, or if you want to use two adapter plates you wouldn't need any metalwork to mount the throttle body.

If you want throttle body based injection then the only thing you would have to do is manifold + adapter, no injector bungs.

Personally, I think I'd weld up a prototype, test it out, refine it, then worry about whether it should be cast or fabbed...

That'd be my .02 cents...

-D.Idiot

Without having seen one, I presume the injectors are placed in the runners right near the port. With an adaptor between the head and intake, how would the extra distance effect fuel delivery?

With the "new" configuration, the distance would be delayed very slightly before making it to the valve pocket. I might be thinking too much into it, but port injection systems do operate in the millisecond range.

The thought also occurs that one could "adjust" the length of the adaptor and create a sort-of hyperpak intake by using longer runners, thus getting the long-ram effect, presuming that the aditional distance doesn't disturb fuel delivery.

Just another .02.

Roger

Sounds like good advice to me.

_________________
Official Cookie and Mater Tormentor.

The part I have is a single aluminum casting, shaped roughly like a cylinder 21" long and 3" in diameter. One one side is a throttle body. On the other side is a set of six holes, each about 1.5" in diameter, with a pair of studs beside each hole.

On the BMW, this bolted to six individual U-shaped runners, which fed into a pair of transition pieces running to the cylinder head. The transition pieces contained the six individual injectors.
The runners are not part of the plenum; instead, I plan to make new runners from scratch, and mounting the injectors in the new runners.
Yeah, that does make sense since there's no telling before I make the first one how well this thing is going to work. I don't know if it will perform better than a carb manifold modified for fuel injection or not. But I can always think of it as practice for when I wind up wanting to make a twin turbo exhaust setup...

Thanks for all the responses.

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair