Let me start off by saying this is not a Holley Vs Edelbrock thread. Both are great carbs and
they both have their attributes and drawbacks. So I will just say that I've always been a fan
of the AFB style carb for street cars, especially with automatic transmission. The Performer
has a hybrid mechanical / vacuum secondary that gives a good seat of the pants boot when
the secondaries open on a performance street engine.
So I've been a fan of the Carter AFB Edelbrock carb on my street cars for many years. Today I
would like to focus on the Edelbrock Performer 1406 with electric choke. This is a popular carb
for the small block Ford and is the trickiest Performer carb to tune. I've tuned a hundred Carter
AFB / Edelbrock 1405 manual choke carbs and they are a breeze. They tune easy and they keep
their tune forever. Which got me to thinking, if the 1405 is basically the same carb with manual
choke, why does this electric choke Performer 1406 give everyone including myself a hard time
with getting the tune right? There had to be a logical explanation. Well after tuning and studying
the Edelbrock manuals I finally figured out the problem.
The 1406 (with electric choke) is tuned by Edelbrock for fuel economy. The 1405 (manual choke)
is tuned for performance. Simple enough. But what if I want an electric choke and a performance
tune? This is what most of us want for our street cars, so we get the 1406 and begin the process
of trying to tune it for a high performance engine.
Edelbrock gives you a tuning grid chart in the manual for your carb and I'm sure all of you that
have tuned an Eddy before are familiar with the chart. It's a real handy reference guide for fine
tuning the jets and metering rods. The problem is the stock 1406 carb is jetted so lean that you
are starting from a whacked benchmark, so even the chart is misleading.
The 1406 has a stock tune of .098 jet and a 075 x 047 metering rod.
That's extremely lean in the cruise mode and can cause hesitation or a stumble as it transitions
to power mode. Most people do two things to try to correct this (both cause the problem to get
worse), either they richen the idle mixture or they increase the accelerator pump shot. Both of
these cause the engine to have a flat spot or a rich bog.
Next logical step is to adjust the metering rod mixture. Because the idle mixture is pig rich, and the
accelerator pump is full rich (from above), some think they're running rich, so they opt for a leaner
tune and it gets worse. Long story short, this is the wrong direction.
Looking at your 1406 chart, tune #24 is one step rich in the cruise mode. But this doesn't solve the
problem either, welcome to the bizarre world of tuning the 1406 carb.
Here's the problem.........
Take that 1406 #24 tune, which is 1 step rich in cruise mode, (1427) .098 jets (1456) 073 x 047 metering rods,
..... and let's locate that setup on the 1405 tune chart below?
That equals a #28 tune on the 1405 chart; 3 steps lean in cruise mode and 1 step lean in power
mode! No wonder your motor is running like crap? Your stock 1406 is jetted 4 steps lean in cruise,
and is still 3 steps leaner than the 1405 even after going 1 step rich!
So here's the simple fix, toss your 1406 tuning chart, and use the Performer 1405 tuning chart.
For a mild/hot 302 engine, just start with the stock Performer 1405 tuning spec as your baseline tune;
That be, 1428 (.100) main jets, 1451 (070 x 047) metering rods, and orange springs.
Set your accelerator pump back to the stock middle position.
Set your mixture screws to 2 turns out (this is a good starting point)
Start the car and adjust the idle stop until you get it to idle between 800-900 RPM
With the air cleaner on, adjust the mixture screws until the RPM drops 50 (don't use a vacuum gauge).
Now take the car out for a test and tune.
The rest of your fine tuning can now be done accurately using the 1405 manual.
The 1406 on my built 302 runs like a champ now with 1405 tune #8 (1 step rich in cruise mode) with
pink springs. Which gave me confidence to share this revelation with you.
Good luck and happy tuning!