Hello everyone-
I am looking for some advice here. A few years back I had a family friend suggest I get a new Carburetor for my 1981 Corvette. He said that it would bring a new life to it since he thought the stock carbs were poorly made.
Is there any truth to this? Now that I have a career I would like to bring some extra life to my Corvette. I am new to doing work on my own car, so I do not even know where to start. Does anyone have any suggestions or advice for a noobie on finding the right Carb and if it would be a good investment?
Also, I have never replaced a Carb on my own car before, but I am able to do the basics such as brakes and oil. I'm fairly confident I could replace the carb by myself. Can anyone confirm if replacing the Carb on a 1981 Corvette is straight forward or am I not taking into account some auto related struggle that may appear?

Thanks in advance. Just found this forum today and it seems the perfect place for me to ask.

 

Keep the stock carb and rebuild it. Nothing will work as well for the car.

 

Being your car came with the "electronic Q-jet" carb, look for a good older ether rebuilt or new non "electronic" Q-jet. Unless you are hopping up the motor with cam, intake and heads, the Q-jet when tuned correctly works flawless under the hot corvette hood. Years ago I had a Holley 750 on my car but it hated the high under hood temps and had to constantly adjust the float levels, Put a Q-jet on it and never looked back

 

Thank you for the response. As of right now I plan to do no work on the motor so that is good information. Ive never heard of this "electronic carb" youre talking about. Any advise on a good article or something where I can research more about my cars parts?

 

Thanks for the reply! When you say rebuild it, is that disassembling it and cleaning the parts/replacing old ones? Total beginner here.

 

If you can do basic stuff like brakes than you should have no problem removing and replacing a carburetor. If your carburetor truly does need rebuilding than send it out to a professional that does this and don't worry about finding a replacement because it will just be a rebuilt replacement.

 

Your car came with an E4ME Rochester Quadrajet.

E - electronic primary metering
4 - 4 barrel
M - ... uh, M (I can't remember )
E - electric choke

Earlier QuadraJets (through 80 except 1980 California cars which also used E4ME), relied solely on air signals on the primary circuit to drive fuel metering/delivery. For part throttle and idle metering, the E4ME relies on computer feedback via the O2 sensor to cycle a solenoid which drives metering rods in and out of the fixed primary fuel jets.

By contrast, mechanical ones relied on vacuum signal to set the metering rod height and pressure differential to control fuel flow on the primary circuit.

The secondary circuit of the two carburetors is the same.

You need a few more tools and a bit more care when rebuilding an E4ME vs an M4Mx, and the M4Mx series is already a bit more complex than the average off the shelf carburetor.

I've done it, it's doable, it'd be helpful to have a mentor with you but there are very few people out there with experience in E4Ms. If you're keeping the car stock and the computer control system is still intact, the E4M is great.

If you want to switch to a fully mechanical carburetor, you'll have to get a mechanical distributor as well, as the 1981 cars used computer controlled spark.

 

If you still have the original carb that came from the factory, it is a hybrid carb: Normal construction except with an electrical fuel mixture solenoid built into it. That carb, along with a one-year only electronic distributor, one-year only ECM, throttle position sensor, oxygen sensor and a single connecting harness for all of that, was the first electronic engine management system on a production Corvette. You CAN rebuild that carb; but it takes a specific rebuild kit and you should rebuild the fuel-mixture device at the same time. That system...when working properly...is a vast improvement over a basic carburetor, as it provides good starting, good curb idle, better economy and all the power the engine can produce. No other carb will perform any better, regardless of what others will tell you. That ECM also controls the lockup clutch in your THM-350c trans, so it is beneficial to keep that system working in your car, if you can.

Also, you CAN upgrade the heads, cam and exhaust system and still use the stock engine management system. It will adapt to those changes without any problem (unless you get to a point when the fuel-mixture control/Q-Jet cannot provide adequate fuel to the upgraded engine). That Q-Jet will flow 750cfm, which is MUCH more than your stock engine will ever need...and likely much more than any upgrades you will make to the engine.

Do some research on that '81 control system and purchase a copy of the 1981 Chevrolet Chassis Service Manual. It will have a wealth of info on your car, on that specific control system, and details on how to check that system out and adjust it properly, should you need to change or rebuild any of the components.

 

Stock 1981 Corvette's came with the E4MC electronic Q-Jet. It has a mixture solenoid on the top passenger side and a Throttle Position Sensor on the side of it. When they work, they work fine.....but when they don't, get rid of it. Every GM car from 81'-84' had an electrocically controlled carb and distributor on it, no matter what it was.....with the exception of the Tech 4 Pontiac engines and the CFI Camaro/Corvette (82-84).
There is just a lack of support now for these and on the Corvette it was a one year only piece. The distributor is also electronically controlled. One can convert to 1980 specs for around $600 in parts.....this requires finding a good 76-80 Q-jet core and having it done as well as a new non electronic HEI distributor.
Why would you want to go backwards? Well, the CCC (Computer Command Control) is not performance based and very little can be done to support mods like camshafts, intakes, headers, heads...etc......in my experience they are also unreliable, and it costs as much to freshen an E4MC as it does just to convert it over to mechanical.
Q-Jet carbs are not poorly made......the ancient first series GM computers and electronics are......and almost nobody knows how to work on this **** anymore either.
You want your car to come to life? Convert it to 1980 specs......do a performance timing curve in the new distributor, and put a real dual exhaust on it with long tube headers.....it will feel like someone put another engine in it.......
SIG is partly correct in his post......you could clean what you have and run it, nothing else will work better......even an older Q-Jet doesn't......but to support upgrades later on....it is necessary. The distributor is the big issue.....it has a **** curve in it and no way to change it.....

Jebby

 

What Jebby says is correct. However, if you live in a State that requires emissions testing, your '81 will need to pass test. If you remove the CCC-controlled carb and distributor, you will either have a "check engine" light on, or you will need to disable the light. Either way, you're not going to pass emissions. You better check your local requirements before you start hacking a nice, stock '81 Vette... just replacing the carb will do little to add performance, but it will make you fail emissions. Fixing the timing curve is what will liven the car up. But you'll still fail emissions...

Lars

 

E4ME. E4MCs don't exist, not that it's not possible. The last character is for the choke type. E = electric, C = hot air choke.

I thought about building a custom ECM for these things back in the day, but it's really just not worth it. Aftermarket TBI systems do all this and more, with better spark control.