E21 Intake Runner FAQ

By Karl Koenig, Bill Barrett and Art (in California)

Updated 5/04/2004

Edited By Peter Florance

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I first heard about replacing 528i intake manifold runners with the corresponding parts from 320i from Metric Mechanic. They advise it when larger displacement engine is swapped in. Then Grassroots Motorsports tried it on their project 528, and got some dyno numbers. It’s one of those things where you say "It can’t be that simple." But it is, and it works. Those bigger runners made a noticeable difference—the butt-force dynamometer registered the difference within a half block of the driveway, the first time I pulled around a street corner in second. This kicks—do it.

Click on photo for higher resolution picture

OK, now for how to do it. Naturally you need 1 donors to get six runners. Local BMW guru found some for me and put them in a box, so I can’t say what came from where on the donor engines, but I ended up with three runners with no studs for hanging stuff, two with short studs, and one with long studs. I also got intake manifold gaskets for 528i at the top and 535i (Karl has E34 3.5L, so the head is a little different - ed.) at the bottom. I used the runner with long studs on cylinder #1 to support the fuel pressure regulator, with left over sway bar bushings to isolate the bracket from the manifold. I used the two with short studs on cylinder #2 and #4 to support the fuel return line and the wire harness on the left side of the engine. (Peter's note: The threaded bosses on the sides of the intake runners are open to the inside of the intake runners. You must install 6mm bolts whether you use them for mounting or not, to avoid a serious vacuum leak. I sealed the bolt threads with sensor-safe Ultra-Red silicone sealer but a teflon sealer or tape will work as well. ) Brackets are home made. The one supporting the pressure regulator started by fiddling with a piece of cardboard to make a template. I also had to reposition the original fuel regulator support to meet the bracket I made. The picture shows how it all ended up. Actually the appearance is kind of subtle.

Have fun with it.

Here's Bill Barrett's installation on a 79 528i (w/ 3.3L) including an adjustable fuel pressure regulator and fuel pressure gauge:

Click on photo for higher resolution picture

Bill writes: "After installing 320i runners, I wanted to add an adjustable fuel pressure regulator and gauge. To make the mounting rail, I used 1" aluminum and 2" right angle brackets. The brackets attach to the studs in the runners and are through bolted into the aluminum. All parts were purchased at Home Depot for less than $10."


Art's FAQ:


320i intake installation
more pictures
the size difference
(one on the left from 320i, rest are from 5 series)
the clean difference
(one in middle not cleaned)
Berryman Chem-dip
the cross brace you need to cut
things you need:
- good ratchet set with at least two different length extensions (some of those bolts are hard to get to..)
- bolts are 12mm
- mounting hrdwr bolts are 10mm
- one hacksaw (I'll explain below)
- scewdriver to get hoses out of the way
- Berryman Chem-dip (this stuff rocks!)
- and of course intakes from up to 79 320i (plenty at your local pick n' pull)
- if you want, 320i intake gaskets (but 528i gaskets work fine and are same size)

parts #s for 320i gaskets:
upper: #11 61 9 065 677
lower (plenum): #11 61 1 730 742

The installation

First off, if you want to clean those junkyard intakes, I went and bought some Berryman's Chem-dip. This stuff kicks. Simply soak your intakes for at least half hour, then use a softer wire brush on the outside (get an extra soft brush for the little corners), and get a soft bristle long stem household brush (the type you use for washing dishes) for the inside. You may need to go through a couple soakings to get your desired cleanliness. After done cleaning, polish them off with a mag-polish (works great).

Hacksaw job:
If you go out and get your 320i intakes, chances are at least two of them will have a crossbrace inside the curve. Plainly put, this will not go around the hard fuel line running along the length of the intakes. So, just cut it off. Hacksaw goes through it just fine.

Other tips:
I found that the easiest way to take off the stock intakes was to start with the one closest to the firewall and work your way forward.
That said, installing the new ones were easiest doing the first 3 (from the front of the car), then working from the firewall with the last intake installed being in the middle. The reason for this if the 320i intakes are of course bigger than the 528's, and subsequently are a little harder to get in, especially the ones near the firewall. Just a suggestion...

Okay.. hope this might helps someone

-art in CA


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