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 in the same boat, let me give you my 2 cents worth of advice. 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 to gain some level of 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 carb more than a few times and also read the carburetor manual.
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 carb comes with.
Not only that but the 1405 Edelbrock is tuned for performance, whereas the 1406 carburetor is aimed at fuel economy and better street manners.
In other words (or numbers, really), out of the box, the 1406 carburetor comes with .098" primary main jets, .075" x .047" metering rods, and 4" Hg step-up springs (yellow), whereas the 1405 carb 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 carburetor 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:
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| Remove the air-cleaner to gain access to the step-up piston cover screws. |
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| 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. |
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| You may need to fish out the step-up spring which can be easily accomplished. |
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| And this is the step-up piston and spring, along with the metering rod. |
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| This is how the metering rod is secured to the step-up piston. |
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| A little pressure to move the spring out of the way releases the metering rod. |
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| The notch at the end of the rod is what keeps it locked in place. |
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| This is the step-up spring kit available from Edelbrock. Part # 1464. |
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| 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," and thank you for following my '76 Vette Blog!
Product Links... (#sponsored)
• Edelbrock 7501 Performer RPM Air-Gap Intake Manifold
• Edelbrock 7201 Intake Manifold Gasket - Pair
• Edelbrock Elite II valve covers
• Edelbrock 7549 Valve Cover Gasket Set
• Edelbrock 1203 Pro-Flo Series Air Cleaner | 10" Round
• Edelbrock 10023 Pro-Flo Series Air Cleaner | Triangular 11" x 8" x 3"
• Edelbrock 1406 Performer 600 CFM 4-Barrel Electric Choke Carburetor
