Carb/Manifold Replacement for ECM Controlled ‘81
Thread Starter
Advanced
Joined: Jun 2002
Posts: 93
Likes: 0
Carb/Manifold Replacement for ECM Controlled ‘81
Despite cash and efforts to tune my car, and the so-called diagnostics of local mechanics, I can’t get it running smoothly. Several mechanics have suggested that the electronically-controlled Quadrajet is shot. I was thinking of rebuilding or replacing it, but am giving thought to replacing the carb and manifold with conventional units. Any opinions? What do I do with the computer system, sensors, etc.? Will the car run smoothly minus this stuff? I want to keep it smog-legal, and was thinking of Edelbrock’s Performer (EGR) manifold and Q-Jet. Can I get away with a less expensive carburetor (Q-Jet=$450)?
Also, when I get all that stuff yanked, what else is logical to do without going for a lung? Head gaskets? New timing chain?
FYI, it’s a replacement engine (4-bolt Chevy 350 truck block) with all stock components save the L-82 cam. Probably around 40-50K on engine.
Thanks to all CF members who’ve helped me in the past – most recently DS.
Also, when I get all that stuff yanked, what else is logical to do without going for a lung? Head gaskets? New timing chain?
FYI, it’s a replacement engine (4-bolt Chevy 350 truck block) with all stock components save the L-82 cam. Probably around 40-50K on engine.
Thanks to all CF members who’ve helped me in the past – most recently DS.
Intermediate
Joined: Apr 2002
Posts: 29
Likes: 0
From: Brewster New York
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
I have an 81 that I put Vortec heads, Holley 600, vac. advance distributer and a new intake. I removed all of the comp. controlls and tucked them behind the engine. No problems to speak of but I also have a 4 speed so I don't have to worry about the transmission. Took the bulb out of the check engine light and left the computer in.
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
Check with Lars to see if he can rebuild that carb for you.
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
If you really want to keep it smog legal, then you need to keep the electronic carb. If you want to get rid of the carb you will need to replace the carb and the distibutor, then you can disconnect the ECM and remove all the sensors and wiring if you want to. The carb is not hard to rebuild if you take your time and get it clean. There are some thread about rebuilding this carb and adjustong them if you search the archives. :cheers:
Thread Starter
Advanced
Joined: Jun 2002
Posts: 93
Likes: 0
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (stickboy)
Thanks for your response, stickboy. Quick question: How do I find the info on rebuilding my carb in the archives? I'm not that familiar with navigating it.
Thanks,
Randy Stuart
Thanks,
Randy Stuart
Abby Normal
Joined: Dec 2001
Posts: 53,456
Likes: 92
From: Press "2" for English
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
custman, any desire to sell/give that ecm away? my diagnostic circuit is dead and replacement is the only fix. :rolleyes: still, i wouldn't change my computer controlled system for a "conventional" (antique) system anytime soon. strickly speaking, mine isn't even street legal but it gets 20-22mpg on the original, tired engine. whose complaining about that?
runner81, it is possible the l-82 cam is the reason for your rough running engine. maybe you could elaborate a little more on what your seeing. if it just has a little vibration and shake at idle, i'd be suspicious of the cam. the l-82 cam was just a hydraulic version of the lt-1 solid cam, quite healthy really, much more so than a l-81 cam. if it's a really wild miss or rough idle, maybe your looking at something that the expense of changing over the carb and distributor won't fix. please elaborate...
runner81, it is possible the l-82 cam is the reason for your rough running engine. maybe you could elaborate a little more on what your seeing. if it just has a little vibration and shake at idle, i'd be suspicious of the cam. the l-82 cam was just a hydraulic version of the lt-1 solid cam, quite healthy really, much more so than a l-81 cam. if it's a really wild miss or rough idle, maybe your looking at something that the expense of changing over the carb and distributor won't fix. please elaborate...
Intermediate
Joined: Apr 2002
Posts: 29
Likes: 0
From: Brewster New York
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (clutchdust)
I believe my ECM is screwed up also...the car ran horrible with the comp. control dist+carb on and always gave a check engine light and just about every code there is....it had them
That was my reasoning for going the way I did. Maybe I don't get very good mileage...but I know it will run
That was my reasoning for going the way I did. Maybe I don't get very good mileage...but I know it will run
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Burning Brakes
Joined: Dec 2000
Posts: 1,183
Likes: 2
From: Des Moines Iowa
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
Runner81:
1st thing to check is for vacuum leaks with hoses, at intake to head area, and carb to intake area. Vacuum leaks will make it impossible to tune.
If carb is "shot", suggest you check with forum member "lars" to see if he can/will rebuild for you.
You could replace OEM aluminum intake with an Edelbrock Performer with EGR provision, but don't expect a big, noticable power increase for the $120, plus gaskets, plus labor(if any) you'll pay to make the switch.
New 'dual pattern' camshaft designs, like Comp Cams XE series will produce more horsepower and give better, smoother idle and more low end torque than the 30 year old L-82 camshaft design.
If keeping your car smog legal includes mandatory passage of a visual exam, then you won't be able to remove and discard all of the emissions control system.
Forum member Dalannex has actual hands on experience rebuilding the carb. on an '81.
1st thing to check is for vacuum leaks with hoses, at intake to head area, and carb to intake area. Vacuum leaks will make it impossible to tune.
If carb is "shot", suggest you check with forum member "lars" to see if he can/will rebuild for you.
You could replace OEM aluminum intake with an Edelbrock Performer with EGR provision, but don't expect a big, noticable power increase for the $120, plus gaskets, plus labor(if any) you'll pay to make the switch.
New 'dual pattern' camshaft designs, like Comp Cams XE series will produce more horsepower and give better, smoother idle and more low end torque than the 30 year old L-82 camshaft design.
If keeping your car smog legal includes mandatory passage of a visual exam, then you won't be able to remove and discard all of the emissions control system.
Forum member Dalannex has actual hands on experience rebuilding the carb. on an '81.
Thread Starter
Advanced
Joined: Jun 2002
Posts: 93
Likes: 0
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (clutchdust)
Dust:
Thanks for the reponse. The car ran very strong for the first couple years, even with the L-82 cam (bought it 4 years ago). The problems now are stumbling on initial acceleration and difficulty adjusting the carb (car runs very rich, not nearly as strong, gets bad mileage). Unless the cam GOT bad over the last two years, it's probably not that.
I don't know for sure what went into the engine because the speed shop that put the engine in is out of business. I do know that the car came to me with L-82 emblems on both sides (yech, an '81 yet), and that the cam was a bit lumpy and strong, but very streetable (decent idle, fine with A/C on, etc.). It's definitely a 4-bolt main Chevy 350 truck block with the correct '81 accessories in place (heads, manifolds, carb, valve covers, air cleaner, etc.). However, because it ran 6-ish 0-60s and estimated 14s, perhaps they did something else (better than orig 8.2 compression, etc.).
Thanks for the reponse. The car ran very strong for the first couple years, even with the L-82 cam (bought it 4 years ago). The problems now are stumbling on initial acceleration and difficulty adjusting the carb (car runs very rich, not nearly as strong, gets bad mileage). Unless the cam GOT bad over the last two years, it's probably not that.
I don't know for sure what went into the engine because the speed shop that put the engine in is out of business. I do know that the car came to me with L-82 emblems on both sides (yech, an '81 yet), and that the cam was a bit lumpy and strong, but very streetable (decent idle, fine with A/C on, etc.). It's definitely a 4-bolt main Chevy 350 truck block with the correct '81 accessories in place (heads, manifolds, carb, valve covers, air cleaner, etc.). However, because it ran 6-ish 0-60s and estimated 14s, perhaps they did something else (better than orig 8.2 compression, etc.).
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
Thanks for your response, stickboy. Quick question: How do I find the info on rebuilding my carb in the archives? I'm not that familiar with navigating it.
Thanks,
Randy Stuart
Thanks,
Randy Stuart
Abby Normal
Joined: Dec 2001
Posts: 53,456
Likes: 92
From: Press "2" for English
Re: Carb/Manifold Replacement for ECM Controlled ‘81 (Runner81)
runner, i have run into a similar condition with mine in the past. turns out it was the MAP sensor. hard to find if you don't know where to look even harder to find a replacement in the parts stores. if you;ve ever noticed that little sheetmetal bracket mounted at the top of the firewall almost right in front of the steering wheel. just unbolt it from the firewall and check that vacuum line connection and unplug the 3 pin connector. put some dielectric grease on the connector and make sure the vacuum boot is not cracked or otherwise leaking. if that doesn't do it, you may just need to replace it all together. then again, it may not even be the problem (?).
