Wednesday, February 10, 2016

Tuning the Edelbrock Performer 1406 Carburetor

Sometimes I end up buying the wrong parts or stuff that's not good enough for the car or my performance expectations. And while I am totally aware that there's only so much performance an L-48 engine can deliver, I would like it to—at least—perform properly and trouble-free.

It is obvious that in the case of the Edelbrock 1406 Performer carburetor, my choices were not the best for many reasons.

First, I was unable to use the factory air cleaner which, although not the prettiest thing on the planet, at least delivered a good amount of clean and cool(er) air to the original carburetor.

I could've had the OEM Rochester Quadrajet rebuilt, but the illusion of more power made me go for the "better" carburetor without taking into consideration a bunch of other changes that not only cost money but may not yield the best results either.

If you are on the same boat, let me give you my 2 cents worth of advise. As the old saying goes, "You can't squeeze blood from a turnip." In other words, an L-48 can only deliver so much horsepower and torque, unless you're willing to break the bank buying hi-performance goodies. So if your goals are HP and torque, buy a crate motor.

A long-block will save you even more, and from such an investment your L-48-powered C3 Vette will go instantly from 185 to 290 horses, with similar torque gains. That's a huge difference and far better than even what the L-82 of the same year yielded.

If, on the other hand, you want to keep your car somewhat stock, but would like a tiny performance improvement, replace the factory intake manifold with an Edelbrock, and have the original Quadrajet professionally rebuilt.

Alas, in my case, after all the time and money spent on the new Edelbrock 1406, I have to see if I can get it to run properly. And after much online research, I think I finally am on the right track.

I've watched the DVD that came with the 1406 more than a few times, have also read the carburetor manual, and from articles I found on the web, I've decided to start this project by replacing the metering rods and springs with those used on the 1405 carb, which is basically the same unit but with a manual choke instead of the electric unit the 1406 comes with. Not only that, but the 1405 is tuned for performance, whereas the 1406 is aimed at economy as well as better street manners.

In other words (or numbers, really), out of the box, the 1406 comes with .098" primary main jets, .075" x .047" metering rods and 4" Hg step-up springs (yellow). The 1405 comes with .100" primary main jets, .070" x .047" metering rods and 5" Hg step-up springs (orange). Secondary main jets are .095" on both carburetors.

I finally have my Edelbrock idling nicely at around 600 rpm (at operating temperature), but it still has a very bad flat spot (sometimes) when taking off from a full stop. From my research it seems the 1406 is running too lean under load, and I want to see if the .070" x .047" metering rods and 5" Hg step-up springs help fix this issue.

Edelbrock has made the task of changing metering rods and springs quite easy, and here's the step-by-step procedure in text and pictures:

Remove air-cleaner to gain access to the step-up piston cover screws.

Use a Torx 15 driver to loosen the step-up piston cover screw and turn the cover to the left.
This allows you to remove the step-up piston, metering rod and spring.

You may need to fish out the step-up spring which can be easily accomplished.

And this is the step-up piston and spring, along with the metering rod.

This is how the metering rod is secured to the step-up piston.

A little pressure to move the spring out of the way releases the metering rod.

The notch at the end of the rod is what keeps it locked in place.

This is the step-up spring kit available from Edelbrock. Part # 1464.

I decided to experiment with 5" Hg (orange) springs.

Installation of the metering rods is the reverse of most of the steps outlined above. Just make sure the piston has some spring to it when fully seated and DO NOT over-tighten the cover Torx screws.

Even though I also have new .100" primary main jets, I will test the new metering rods and step-up springs first, and based on those results I may decide to give the new main jets a try.

Stay "tuned."