Just bought an 81 corvette
Thread Starter
2nd Gear
Joined: Jan 2022
Posts: 2
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Just bought an 81 corvette
My question is I see there is no vacuum advance, so I’m guessing it’s controlled by the computer. The car appears to be all stock. Can I change out the Qjet for a Holley or edelbrock? Also can I go back to a vacuum advance distributor? There is a wiring harness going to the carb which appears to be butcher up. There is also some kind of module next to the distributor with vac going to the carb. Can that go away?
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
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From: New Braunfels Texas
If you change the carb to a Holley or Edelbrock....you will need to change the intake....DO NOT use the dreaded Square bore to Q-Jet adapter.....it is a terrible thing that should not be sold to the public. You will have nothing but grief......
Find a 76'-80 Q-Jet....a good rebuildable core on E-Bay or other sites........E-Mail Lars (v8fastcars@msn.com) for his papers on how to find a good core. Send it to him to be freshened......
Buy a premium HEI distributor (Non-CCC) and drop it in......curve it and install an adjustable vacuum advance or a stop......
There is really nothing better to use on the stock 350 other than a nice freshened Q-Jet.......
Jebby
Find a 76'-80 Q-Jet....a good rebuildable core on E-Bay or other sites........E-Mail Lars (v8fastcars@msn.com) for his papers on how to find a good core. Send it to him to be freshened......
Buy a premium HEI distributor (Non-CCC) and drop it in......curve it and install an adjustable vacuum advance or a stop......
There is really nothing better to use on the stock 350 other than a nice freshened Q-Jet.......
Jebby
Thread Starter
2nd Gear
Joined: Jan 2022
Posts: 2
Likes: 0
Not having problems, just got it. Never been a bug fan of Qjets. My concern was all the wiring that’s running to the carb. Can that all be disconnected without issue? I already have a hei distributor with vacuum advance. Just wanted to make sure there were not going to be any issues putting it in.
Banned Scam/Spammer
Joined: Aug 2020
Posts: 171
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From: Warren, Mi
If you change the carb to a Holley or Edelbrock....you will need to change the intake....DO NOT use the dreaded Square bore to Q-Jet adapter.....it is a terrible thing that should not be sold to the public. You will have nothing but grief......
Find a 76'-80 Q-Jet....a good rebuildable core on E-Bay or other sites........E-Mail Lars (v8fastcars@msn.com) for his papers on how to find a good core. Send it to him to be freshened......
Buy a premium HEI distributor (Non-CCC) and drop it in......curve it and install an adjustable vacuum advance or a stop......
There is really nothing better to use on the stock 350 other than a nice freshened Q-Jet.......
Jebby
Find a 76'-80 Q-Jet....a good rebuildable core on E-Bay or other sites........E-Mail Lars (v8fastcars@msn.com) for his papers on how to find a good core. Send it to him to be freshened......
Buy a premium HEI distributor (Non-CCC) and drop it in......curve it and install an adjustable vacuum advance or a stop......
There is really nothing better to use on the stock 350 other than a nice freshened Q-Jet.......
Jebby
Instructor
Joined: Nov 2020
Posts: 189
Likes: 54
From: Orange Park, Fl.
qjet carbs are pretty much qjet carbs until the electronic controls of the metering rods in 81 and newer came out. tune of the metering rods and jets may need to be done if from another vehicle not a vette. 73 -80 are considered 800cfm. Prior to 73 they were 750 cfm. some choke differences and fuel inlet hookups exist also but does not prevent their use.
Race Director
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From: Sunshine Coast, Queensland, Australia
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Congratulations on your new to you Corvette! And a big welcome to the Forum!
If it was my 81. well, I would most likely change the intake manifold and add a throttle body EFI system.
But at the least, I would change the intake manifold thus cleaning up the look of the engine a great deal. loosing the EGR, all of those unnecessary wires and vacuum lines.
If you put on a aftermarket intake manifold then yes the Holley will bolt on. Of course you will need to change fuel inlet line, throttle cable mount, all vacuum lines will be in different places including the big one to the brake booster.
Yes, I would put in a properly curved HEI with vacuum advance.
If it was my 81. well, I would most likely change the intake manifold and add a throttle body EFI system.
But at the least, I would change the intake manifold thus cleaning up the look of the engine a great deal. loosing the EGR, all of those unnecessary wires and vacuum lines.
If you put on a aftermarket intake manifold then yes the Holley will bolt on. Of course you will need to change fuel inlet line, throttle cable mount, all vacuum lines will be in different places including the big one to the brake booster.
Yes, I would put in a properly curved HEI with vacuum advance.
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Verdad Gallardo
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
If you wanted a car to "play with" and swap parts on, you made a bad choice with the ECM-controlled '81. Removing or disabling the carb, distributor, or other ECM components will set the "check engine" light. If you want to "tinker" with a Vette and do what you're wanting to do, sell the '81 and get an earlier year.
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While I am certain Lars is correct about the check engine light. I am thinking that in and of itself wouldn't be much of a challenge to overcome.
None the less I believe that their are other issues that will raise their ugly heads. Now I'm not certain about this particular car. But I believe most 81's are Automatic transmission cars. If this car is an Auto. is it not true that the ECU controls the lock up on the converter? Mind you I own a manual 77 so I am no expert here.
But there will be a number of little hurdles to clear to get this car working like a slightly older one.
These are really good looking cars. And the O.P. already has it.
If it were me, I would persevere and clear those hurdles.
A check engine light from a car of this time period. Pretty easy to disable.
None the less I believe that their are other issues that will raise their ugly heads. Now I'm not certain about this particular car. But I believe most 81's are Automatic transmission cars. If this car is an Auto. is it not true that the ECU controls the lock up on the converter? Mind you I own a manual 77 so I am no expert here.
But there will be a number of little hurdles to clear to get this car working like a slightly older one.
These are really good looking cars. And the O.P. already has it.
If it were me, I would persevere and clear those hurdles.
A check engine light from a car of this time period. Pretty easy to disable.
Race Director
Joined: Mar 2017
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From: Virginia
If you want a cool car to tinker with, an 81 is a fine choice. You'll have no reason not to swap the engine, and you can fix the fuel and ignition while you are in there (i.e. replace them with 80-spec parts, or modern equivalents, and eliminate the ECU).
Even better if it has a 4-speed, or you plan to upgrade to a 5 or 6 speed.
Please post some photos!
If you live in California, Lars' advice is spot-on.
Even better if it has a 4-speed, or you plan to upgrade to a 5 or 6 speed.
Please post some photos!
If you live in California, Lars' advice is spot-on.
Drifting
Joined: Aug 2017
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Just for balance, my bone stock '81 runs all original carb, computer, ignition etc and runs great - starts well, instant response, no hesitation or flat spots, good mileage. In my limited experience, when its working, it works well. Not a power house for sure, but does what its designed to do very well.
I'm sure when they go wrong they're a 'mare, but until that day, I'm more than happy with the stock set up. If it's working, leave it alone is my guidance, but depends on your wants and needs.
I'm sure when they go wrong they're a 'mare, but until that day, I'm more than happy with the stock set up. If it's working, leave it alone is my guidance, but depends on your wants and needs.