The R2 Project: Carb improvements

[ronmanfredi]

We recently purchased a 1963 R2 from a long time Avanti owner, who bought it to restore. He got the drive train, suspension, brakes and fuel system done and decided he couldn’t go any further due to age.  I knew that this was the time to purchase this halo car and that I wanted to complete this now "custom restoration". (If you've seen our 2006 Avanti, then you'll understand).  I was an educated auto tech in the 70s-80s which provides me an edge on working on cars of this age.  Right out of the gate, I saw a problem with the carburetor on cold starts.  With the choke operational, the car would run extremely rich on cold starts since the choke plate would remain almost fully closed.  Most carbs have a vacuum operated choke pull off diaphragm which prevents this, but not this one.  In doing some research, it appears that Carter never provided this on this model carb.  So, I started looking and found a GM choke pull off that I thought would work.  I also found a linkage piece that I hoped I could use to connect it to the carb choke plate arm, in an oversized available hole in it.  First was to mount the pull off using one of its brackets mounting holes along with cutting a notch in the bracket to fit tight up against the carb.  Once done, the next thing was to start experimenting with the linkage until it worked correctly with the choke fully closed and let the choke plate open all the way without binding as the car warmed up.  I probably bent it 15 “small” times until it worked the way that I needed it to.  Lastly, was to connect the vacuum line to the intake manifold.  With all of this done, I did a cold start and the car started right up, the choke plate opened with around a 1/4" gap and the car idled perfect.

Both carb parts came from eBay.  The Choke Pull off is Rochester 17050733 for 1975-1976 Oldsmobile 455 engine.  The link was a secondary vacuum break link for 1968-1974 Quadrajet Carbs.

Next, I had added a custom modern Air Conditioner/Heater system to the car and needed an idle solenoid to raise the idle speed when the A/C was on since the car has an automatic trans.  In looking at the limited options available, I chose the Standard Motor Products ES9 Solenoid, without any bracket.  Holley offers the same solenoid with a bracket that might work, but they are charging over $150 for the bracket itself.  I knew I could make one for labor only using some scrape aluminum angle iron that I had laying around.  Once I cut the basic shape, drilled the 2 holes needed, and notched the bracket to fit tight on the carb, the bracket lined right up.  I smoothed out design and started up the car and it worked like a champ.  The spindle that pushes the throttle is adjustable and comes set midway in the range.  I didn’t have to make any adjustment at all.

Here are a few photos.

[mfg]

The idle speed ‘kick up’ is a good idea… Studebaker offered a retrofit kit for Avantis with A/C that accomplished the same thing…..

However, the GM choke pull off shouldn’t be necessary if an R2 carb is adjusted and working properly, the intake manifold crossover passage is clear, the correct intake manifold gaskets are installed, and the heat riser valve is in place and working properly.

[mfg]

Also…. It’s important that the Carter AFB’s internal vacuum passage is clear and pulling warm intake manifold air up the choke tube and into the choke housing… This is critical on AFB’s for the choke valve to open in a timely fashion!

If a Carter AFB carburetor, as used on a Studebaker Avanti, is set up properly, ‘band aids’ such as choke pull offs or electric choke conversions are completely unnecessary.

[ronmanfredi]

12 hours ago, mfg said:

Also…. It’s important that the Carter AFB’s internal vacuum passage is clear and pulling warm intake manifold air up the choke tube and into the choke housing… This is critical on AFB’s for the choke valve to open in a timely fashion!

If a Carter AFB carburetor, as used on a Studebaker Avanti, is set up properly, ‘band aids’ such as choke pull offs or electric choke conversions are completely unnecessary.

I was a carb/fuel injection specialist in the 70s and early 80s.  All carbs need a choke pull off to prevent over enrichment AFTER cold startup.  The choke on the carb works great.  It closes completely at start and the heat rises correctly and opens the choke all the way up.  But the 1-2 minutes that it takes to warm up enough to open the choke is where the over enrichment becomes a problem.  I solved it once and for all.  BTW, most other Carter AFBs come with choke pull offs.  The model carb on my R2 is listed as one that does not. It's a simple thing compared to tuning 3 solex side draft carbs, which I can do and still have the balance and jetting tools to do.

[mfg]

3 hours ago, ronmanfredi said:

I was a carb/fuel injection specialist in the 70s and early 80s.  All carbs need a choke pull off to prevent over enrichment AFTER cold startup.  The choke on the carb works great.  It closes completely at start and the heat rises correctly and opens the choke all the way up.  But the 1-2 minutes that it takes to warm up enough to open the choke is where the over enrichment becomes a problem.  I solved it once and for all.  BTW, most other Carter AFBs come with choke pull offs.  The model carb on my R2 is listed as one that does not. It's a simple thing compared to tuning 3 solex side draft carbs, which I can do and still have the balance and jetting tools to do.

Over the years I’ve worked on ‘a few’ Studebaker Avantis both R1 and R2.

Living here in the rather cold northeast, carburetor choke issues (back when cars had carburetors) were quite common… so I do understand what over choking an engine looks, sounds, and smells like!

The only time I’ve had choke issues with those early Carter AFB’s (going back to a 1958 Imperial I maintained) was when a component in the system (as I described previously) was misadjusted or not working properly…..

Those carburetors were not designed for and DO NOT NEED a vacuum choke pull off.

However, the bottom line here is that it’s your car, your carb, and if you’re happy with the modifications you’ve made… that’s all that really counts.

Keep swinging!!!…. Ed