EFI Intake Conversion (2 of 2)

[Frederic Breitwieser]

> Could we keep this on-list??? I'm starting on the same thing too. Just
> picked up some of that aluminum 'brazing' rod last night ($19.95 per
> pound at the local welding supply).

The second thing I will discuss is how to make an intake from scratch.  This
was done for a Buick V6, however the same methodology applies to just about
any motor.  Entirely made of aluminum, brazed together using the alumaloy
propane-heated welding rod (durafix is pretty much the same thing).

To visualize what I was trying to achieve, I wanted more flow, straight
runners, a huge plenum, and a plenum-installed water based intercooler in
one package.  Autozone didn't have any in stock <grin>.

I took the "Buick Power Source" which has all the dimensions of the heads,
blocks, and intakes, including OEM & Stage I, and Stage II components.  I
took the dimensions off the head diagram for the intake side, simply
transposed it to a 3/8" thick aluminum plate.  Drilled the bolt holes, and
milled out the intake ports.  Then, I whipped out a circular miter saw,
replaced the wood blade with a grinding disc, then cut 1"x2" rectangular
tubing (outside measurements) at an 20 degree cut on the miter saw for the
head plate end.  Then, on the other end, 15 inches away, I cut a 55 degree
cut (I think) to match the 45 degree plenum shape I was to have.  After
making six identically shaped intake runners, I then made a plenum.  The top
of the plenum was a rectangle, and the front or back view was a triangle if
that helps you picture this.  This was the bottom half of the plenum.  I
marked everything off with a marker, drilled and milled the openings for the
runners, then pushed it all together.  Once things were set, I allumalloy'd
everything together for the bottom half of the intake (80% at least).  Now
comes the intercooler portion.  I found an aluminum oil/transmission cooler
ahead of time, measured it so that my plenum would be a tad larger, then
installed the cooling unit on side pieces I made and welded that to the
bottom of the plenum.  Picture a rectangular box 2" high without a top or a
bottom that's the same size as the top of bottom half of the plenum.  Once
that was together, now comes time to make the top half of the plenum.  I
made an aluminum box using .120 thickness material as I had for the runners
and the bottom of the plenum, drilled out holes for the two throttle body
units, drilled mounting holes and alumalloy'd in aluminum nuts that I had a
hard time finding, then welded this piece to the intercooler piece, so its
all once large piece now.  The cooler fittings came out through the side by
the way, and I added a ring of welding rod (alumaloy) around both fittings
as to keep an air tight seal, as I did with the cooler and the 2" high box
it was in anyway.

The injector bungs went in at a 30 degree angle to the intake runner sides,
and how that's done is by following the previous message I sent (1 of 2) -
same process).  The equipment I had to make this with was a smitty milling
machine at a friend's place, so getting angles correct was fairly easy
compared to at home with just a drill press.

Anyway, the last piece was the intake manifold bottom, or valley cover.  The
buick engine needs a hard cover, and its sorta trapazoidal shaped.
Measured, cut paper template, and made such a piece, then grinded the edges
to fit, then welded in.

I must admit that the use of paper templates and scotch tape is a good
idea.  I made two manifolds before checking the fit closely enough, which
obviously is a waste of time, material, and money.  I hate to admit to
stupidity, however check each and every step twice to be sure you have it
right, if you haven't made a much of intakes before.  Its a lot more
challenging than I'm describing.  In fact, the third manifold I made for the
Buick V6 was entirely out of cardboard from the back of legal pads taped
together, using corragated box cardboard for the head plates and the bottom
plates.

The only thing I screwed up on the final version of the intake was a hot
water crossover from head to head.  I somehow, (duh) left that out but I
caught it before I actually used it, and ended up with two brass fittings
with a larger diameter than the not-so-round holes for the coolant
crossover, and a piece of tubing with two circular hose clamps.  The beauty
of alumaloy (or durafix, whatever) is as long as the metal is non ferrus,
you can make dissimilar metals stick to each other very well.  Brass,
copper, gold, aluminum, etc.

Hope that helps you out.  If you are converting a carb intake to EFI, the
article in the mopar mag has a three-article thing on it, and is written
well enough that you can follow along.  The pretty pictures help :)

--

Frederic Breitwieser
Bridgeport CT 06606

1993 Supercharged Lincoln Continental
1989 HWMMV w/turbocharged 500cid Caddy
1975 Dodge D200 Club Cab soon to have 431 stroker + turbos
2000 (I hope) Buick GTP (Mid-Engined Sports Car)