Quadrjet Install on a 1973 Ford Bronco 302 CID

 

For eleven years or so, I have been running the very popular Edelbrock (Carter) AFB 625 cfm carburator.  For the most part, the AFB kicks ass in the dunes and on the trails, but not in the off camber stuff!  I have countless stories of that AFB going south on me right when I needed her most.

We've all made that argument in our heads "fuel injection or is there really something else?"  I could not pony up $1500 to do the TBI set up right.  I will go through Turbo City when it's time to go TBI.  If I get rich, I will go with the Edelbrock Port Injection, but that's $2,500 (includes shipping).  All promise great reliability and power......

So what do you do when you have a couple hundred dollars in the bank, (comma) and your Bronco hasn't had an upgrade in a week or so?? Buy more Bronco parts! Chuck at BCBroncos recently advertised their new Bronco-ready Quadrajet. People have hyped it up as "The poor man's injection". Hmmmmm... could it be?

Don't know if you have ever bought something through BCBroncos, but they are top notch!  Personalized service on every sell!  I gave Chuck a call and had a Quadrajet and adapter on the way.

 

This is what you get in the box from BCBroncos.  Carburator, gaskets, adapter kit which includes all the mounting hardware and a coil wire. 

Here's a side by side comparison of the two carburators.

I went out to the Bronco and started taking off the Edelbrock carb, fuel line, pcv hose, distributor vacuum, throttle linkage and kick down. 

Once you are down to your manifold, be sure the gasket surface is very clean.  Install the adapter plate with the carburator bolts installed from the bottom like in the picture.  It wouldn't hurt to put a rag in the manifold in case you drop a bolt.  Nothing worse then trying to fish a bolt out of a manifold.

Once the carb was installed on the adapter, I had to figure out what to do about the Bronco linkages.  The throttle linkage was going to work out fine, but I would have to get creative with the kick down.  Now that I was at this impasse, I had remembered a fellow Bronco driver experiencing unwanted throttle actuation from the body flexing seperate from the motor.  The cause severe damage to his truck.  I thought it was time to go to a cable.

I visited So-Cal Vintage Ford Parts in Phoenix, AZ.  They are one of the local Lokar retailers.  After talking to the salesman I came home with a bag of goodies!  I decided to go with a cable kickdown (very easy conversion), new gas pedal, return spring set, and of course, the throttle cable.  Lokar makes some neat stuff!  Very easy to configure, adapt and looks great under the hood.

Here's a real clear pic of the cables installed.  It took a little bit to get the carb to run smoothly.  Dave had come over and help me get the most vacuum at an idle.  Seventeen inches was the max. 

OK, what do I think about this carburetor?  Initially, I could not get used to starting it on cold mornings.  I would inevitably flood it out until I learn to push the gas pedal 1/3, before I started it.  The old carb was once to the floor to set the choke.  I did have more power in cruise, but I had lean conditions if I romped on it.  When it is warm, it's the fastest starting carb I have ever seen.  Varrrrooom!  No hesitation.  Offroad it excelled in every arena over the Edelbrock, except when going straight up.  It just cuts out.  Very disappointing. 

I had heard about turning the carb around backwards to overcome this problem.  Chuck said that I shouldn't have to do it, but I was left with no option if I was going to run this carb.  It was very easy to turn around backwards.  I had to get a longer throttle cable since I had cut the other one so short.  The kickdown cable just moved to the other side.  I made my own bracket to mount the cables to the other side.  I will get a pic of the new configuration soon...........

Once I had a month or so with this carb I learned a lot more about it.  Plus, it was like the carb went through a break-in period.  With the carb turned around, I have never stalled the truck in an off camber situation.  Awesome!  A new sense of confidence in my truck. 

Two other friends and I run the Quadrajet on our Broncos...... and all have some common quirks to them. Not all are Chuck's either..... One thing we noticed is how sensitive the Qjet is to vacuum. None of our trucks idle the same every time we start it. Vince's is a 1969 351W, Todd's is a late model 302 crate roller motor and mine is 1973 vintage 302....... I was chatting with a
friend of mine while tearing down my engine. I had experienced the back two cylinders getting really lean and the header tubes glowing hot. He said running certain adapter plates could cause anomalies like that, along with erradic idle and off idle stumble. Having the 1" of open plenum before it goes into a dual plane manifold (we are all running Edelbrock Performers) causes a swirling of air/fuel and uneven flow to all the plenums. Don't forget the Qjet likes to see "even" vacuum across the base of the venturies. Talking
with Vince, we were going to do some machining to Chuck's adapter to partition the left and right side. However it was labor intensive and needed a matching gasket to do it.

The adapter sent with Chuck's Quadrajet

Well, I was at Autozone and saw an adapter plate to use a Carter AFB carb on a Qjet manifold (PN 5775). I got to looking at it and realized you could just flip it over and the general shape of the adapter would be correct, but, the bolt hole set up was incorrect. Vince took it to work and drilled out the holes to accept allen-head bolts to hold it to the manifold, and we heli-coiled the adapter holes and used bolts to hold the carb on. Now each Qjet venturi has a runner into the manifold.

Sold at Autozone (Spectre PN 5775)

I hope all this made some sense..... Ok you are asking.... did it make a difference? HELL YES.... touch of the key and it starts right up, idles very smooth, no off idle stumble anymore...... I have fantastic vacuum at idle and cruise... I have not run it hard in the sand to see if the lean condition is still there in the back cylinders, but my gut feeling is that it is gone too......

We are still working on the adapters for Todd's and Vince's Qjets...... we'll see if they have the same experience....
See all the install pics
   
Techincal article and photos are copyright 2003, Motoman's Madness.  Do not duplicate without express permission from Greg Banfield aka Motoman!

Return to Motoman's Madness