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Old 06-22-2013, 06:25 PM
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'94 SAAB 900, carburetor swap.

Hey guys,

Seeing as how my hot rod is down until I can tear it apart and replace the heads. I've decided to put some work into getting my commuter running better.

I picked up this SAAB on a mechanics lien, it was dropped off at the shop for a cooling fan replacement. After 4 years of failed attempts of contacting the owner the title was applied for and granted.

I have driven this thing all over the west coast. Phoenix to San Francisco and back, Vegas and back, Utah and back, Los Angeles and back over a dozen times. It really has been a good little car, I gutted the interior to make way for moving music equipment and when I moved to L.A. I commuted this car back and forth between Hollywood to Long Beach and back everyday. I even raced it for a TV show.

Now living back in Arizona I have been spending more time behind the wheel of my hot rod truck, in the meantime my commuter has developed some problems. Miss-fires, erroneous MAF code. Lack of power and drastic increase in fuel consumption. I've replaced all the intake gaskets, replaced the MAF, TPS, FPR. I've chased wiring back to the ECM and replaced ignition components to no avail.

The carburetor swap idea spawned from a joke with co-workers " I might as well, nothing else is working". Then I looked at the intake manifold, aside from the small plenum the long runners could actually make a good carb manifold. The top of the plenum is flat enough to mount a 2 barrel too. So I went for it.

I hopped online and found a used 3 piece intake manifold set for the engine cheap. I also found a performance 2 barrel carb, spacer and fuel pressure regulator.... also cheap (relatively speaking).

The carb, a Weber 38/38 DGES:

Plugging the IAC and fuel injector ports:

Drilling the plenum for the carb:

The bolt down:

After bolting it down, making sure the fuel pressure was in check and no leaks. I gave the key a turn. It fired up in half a crank. I couldn't believe, it immediately idled smooth and when the throttle blades open it revs without any bogs or hesitations.... again, I couldn't believe it.

I know the carb is backwards, I wanted the aesthetic of the throttle gears in view.

I noticed a few vacuum leaks, I took care of that and went for a drive. Accelerates smooth, it's not fast by any means (never was). It's got plenty of torque and runs smooth.

Here is a short build video (using the same pics in this thread) with a start up, idling and revving:


I'll start commuting back and forth to work next week with my SAAB Rat Rod (?) and will see how it does on fuel. Then to scour junk yards for a hood to cut.

Cheers ~Mykk


Last edited by 04SilveradoMykk; 06-22-2013 at 06:42 PM.
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Old 06-25-2013, 06:56 PM
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I've been driving it for a couple of days now, dealing with the growing pains of uncharted territory. Getting the idle consistent and reliable took some work. The idle would vary from 900rpm (where I set it) to 400rpm and than all the way up to 1800rpm or higher. I thought I was searching for a vacuum leak, toop the 3 pieces of the intake manifold off. Re-gasketed, JB welded the throttlebody block plate in black (and four corner screws), also JB'd over the pipe plugs blocking the fuel injector holes.

Re-sealing the intake didn't solve the hunting idle so I unplugged the 02's to force the ECM to stay in open loop. This helped a bit, but not entirely. Unplugged the c from the ignition timing equation. That also helped, but didn't cure it completely. Driving around today I noticed that the throttle blades would actually stay open with manifold vacuum, the built in clock spring on the throttle shaft just wasn't strong enough to counteract decel vacuum. So I added a throttle return spring:

I also started to work on mounting a TPS to the carb in hopes of allowing the ECM to have a better idea of ignition timing advance.

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Old 07-27-2013, 12:19 AM
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I decided to rid of the upper intake manifold and make my own plenum for a dual carb set up:

I'll bolt it on in the morn and give it a fire
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