 DIY
Intake Manifold Basic
Written by Ryan K.
Materials:
1) 12" of half-round plenum extrusion from RossMachineRacing.com
(RMR - 043)
2) Two universal half-round vacuum endcaps from RossMachineRacing.com
(RMR - 048)....one normal and one not tapped
3) Custom cut stock TB flange (from Brad D.)
4) 12" of 2.5" ID 6061 aluminum straight pipe
5) 1/4" NPT brass barbed fittings (blow-off valve,
boost gauge, fuel pressure regulator, boost controller signal and brake booster) from McMaster.com
6) Nuts and studs from NAPA to hold plenum to stock upper
runners
7) 2 sets of intake gaskets for test fitment/drawing/grinding
and final installation
Tools:
1) 28 degree inverted taper carbide burr from American-Carbide.com
(2152002)
2) Die grinder
3) Several die grinder misc. wheels (round stone, cone,
etc)
4) 40, 220, 400, 600, 800, 1000 grit sand paper
I first test fitted the half round
plenum on the stock upper runners in the engine bay to
make sure everything will fit. Then I sketched an outline
of the gasket onto the new plenum.
After that, I started cutting away
with my die grinder to match the gasket outline. So basically
you match the gasket on both the plenum and the upper
runners flange. Once its close to the edges, then use
the inverted taper carbide on the die grinder (facing
the mounting plate of the plenum).
Make the entry really smooth. Sand
the ports with sandpaper and make sure there are no sharp
edges or burrs.
Once the ports are done, drill out
two small holes which line up with the holes on the mounting
flange of the upper runners. Basically this will help
you run 2 bolts through so you can put a nut on the other
side and then the plenum will be fastened to the runners.
After that, drill out the rest of the holes through the
top of the mounting flange (so the drill bit doesnt move
around) and make sure to use the corresponding drill
bit size for the tap size you are going to use. Once
all the holes are tapped, run the studs into the plenum
and tighten nuts onto them...For the throttle body, just
mark its spot in the middle of the front end cap, draw
your 2.5" tube onto it and cut that hole with a
hole saw. Then its handy to have the 2.5" tube welded
onto the end cap and the TB flange welded onto the tube
so you can smooth the entry of the endcap port into the
plenum...Once thats done, then you can have both endcaps
welded onto the plenum.
Then just run your barbed fittings
in with thread tape. Then put your gaskets on and install
it.
Other things to consider:
- Making a bracket for the TB cables. Can be as easy
as running a longer bolt through one of the TB mounting
holes and bending a bracket to fasten on the other
side of the bolt. And then you cut a "U" shape
so that the throttle cable can lock down on
- Whether or not you want the IACV...You can make a port
for it on the plenum or get the remote mount IACV from
Xcessive and tie it in that way
Modification Justification:
I know this plenum isn't the most efficient design out
there, but I'll explain the reasons why I think it
is beneficial. The main reason I wanted something like
this, is that the stock plenum is vulnerable for boost
leaks...And boost leaks/less air = less HP....I tapped
out the PCV re-entry ports on the runners to 1/8" NPT
and put plugs in there. Now I no longer have to deal
with leaks there or at the EGR or IACV which I no longer
have. It also elminated 5-6" of runner length
which the stock lower plenum has. Then some people
ask "why arent there velocity stacks?" The
stock plenum didnt have any and the port entry was
radiused so I figured I would do the same.
Total costs ~ Less than
$200
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