Custom L6 intake manifold

[Oddmanout84]

A little while back, I stumbled upon this on ebay and got it for a ~relatively~ low price. It was marketed as an unfinished RB26 intake manifold. Unfinished is right, as the only parts included are the shaped plenum and a backing plate. Besides being polished, the casting looks like it was made in some guy's back yard by pouring a crucible of molten aluminium into a shaped hole. But at least the outer surfaces were polished!!! I have had visions of the casting failing under positive pressures, intake shrapnel tearing through the hood. A little paranoia there. Whoever made this did a better job than I could though. Still, seemed a bit interesting to try to give a go at fabricating an intake for the L6. Maybe not as easy as buying a Lone Wolf intake, but more fun than stabbing yourself in the eye with a rusty spoon.

 

 

I intended to turn it into a sort of pet project to eventually go on my L28ET when the time was right. However, there was no size reference in the photographs. When I got it, I realized quickly that this thing is HUGE. Hopefully not too huge. I certainly wouldn't run a manifold like this with my dinky stock T3 setup.I don't even think I'd even run it with the TO4e hybrid I'm currently assembling, as the compressor is .50AR. Plan down the road is to weld some velocity stacks on the inner side of the backing plate, and figure out what type/size of runners to use. I found a thread on another site (I think Zcar.com) where 1-fast-z was talking about the ideal length for the runners can be determined using an equation, which optimises the flow for the engine RPM. I also remember seeing a custom setup in a recent Nissan Sport magazine where the owner used what looked like triple Webber runners with 12 injector bosses, one primary at the stock location and secondaries farther up. That would be the easiest option I guess, maybe not the cheapest. I don't think I want to use ITBs anyway, I figured I'd just weld the flange for either a KA24 or larger Q45 throttle body on the intake.

 

Any commentary is welcome of course, even if it is something like its-too-big-you-idiot. Its a long term project, mostly for fun, and I WILL be trying to use as much research as possible as I construct it. I'm just curious if anybody has any input.

Edited March 6, 2011 by Oddmanout84

[lowrider]

That thing is massive! I've been thinking of fabricating my own intake manifold as of lately. I saw an "RB25" plenum on eBay, but just couldn't bring myself to pay that much for something I could make. I'm glad you posted this, really solidifies the decision to not buy the RB plenum.

[BluDestiny]

I think someone sells flanges for the intake on L series heads. If you can get one of those you can just add the runners (any length you want) and fix that plenum to it. IT does seem to be a little long, so you could chop the rear off and add another back plate. Then it won't seem as large or bulky

[Oddmanout84]

That thing is massive! I've been thinking of fabricating my own intake manifold as of lately. I saw an "RB25" plenum on eBay, but just couldn't bring myself to pay that much for something I could make. I'm glad you posted this, really solidifies the decision to not buy the RB plenum.

 

 

I wouldn't entirely rule it out. if you look at the photo, you can see that while the N42 intake plenum is MUCH shorter than the custom plenum, the runners curve outward to the ports on the head and brings it much closer to the length of the RB26 plenum. So you could easily (I use that word VERY loosely) use straight runners to connect to the head. I'm also pretty sure this plenum is larger (at least in girth) than the standard fare RB26 intake.

Edited March 6, 2011 by Oddmanout84

[Isaiah]

Intake flange

http://bandmzcars.com/IntakeFlanges.html

 

And parts that could

http://rossmachineracing.com/intakepartspage.html

[Oddmanout84]

NICE links, thanks! Its too bad that they discontinued their 1.625" stuff, since that's what the stock diameter is close to. I can always have it taper in slightly.

[Isaiah]

My post was truncated...user err.

 

For intake inspiration I forgot to include:

 

http://forums.hybridz.org/index.php?showtopic=51825 < best ending ever

 

and

 

http://forums.hybridz.org/index.php/topic/61549-turbo-intake-plenum/

[Oddmanout84]

My post was truncated...user err.

 

For intake inspiration I forgot to include:

 

http://forums.hybridz.org/index.php?showtopic=51825 < best ending ever

 

and

 

http://forums.hybridz.org/index.php/topic/61549-turbo-intake-plenum/

 

 

I read both of those a while back. Simply amazing stuff. I can never hope to create something like what Monzter did, and didn't trust my fab skills enough to do something similar to RTz's manifold. That's why I picked up the RB26 intake plenum, so all I had to worry about are the runners and flange. When I get all the pieces in order, I'll have to take a trip down to my Uncle's place, since he has a TIG.