Hello everyone,

I have a friend's '81 'vette. She got a KILLER STEAL on it, and it's always been her dream car. But it has issues. And I need pro vette owner/ mechanic level advice to save my time and her money so it will go the furthest for her. She IS willing to put money into it within reason. But I need help to sort what the best approach for her would be:

The biggest one is the ECM controlled Quadrajet wouldn't idle. It would if you constantly held it slightly open, and blipped the throttle. But "maxxed out" @ 2500, meaning I never floored it, but like it was starving for fuel "breaking up" above that. I have a feeling it was the TPS. I pulled the lid, no excessive flooding, float not soaked, bowls full, but not overly so.

It also has a curious drain on the battery. While it's running, the volt meter goes up to almost 14V, acts like the alternator is working fine. But when I disconnect the battery after shutting it off, and put a charger on it, the battery takes charge like the motor was running strictly on the battery, maybe even MORE than that for the time running? SO it seems a heavy short SOMEWHERE. Hell, I haven';t even found the damn fuse box yet, and HAVE looked.

I also have a driver's door window "off track" as she puts it. Down in the door. So I have that to deal with too.
Forward reservoir on Brake MC was completely empty , so that's on the list too.
Losing coolant somewhere as well...

So yeah lots to do. I am trying to help her out, but unfamiliar with 81 vette "quirks".

My questions are to ask advice as to the best plan of attack, so she can drive her car with little fuss, when she wants. LESS gremliny issues later.

I am worried about vacuum hose routing as that is already fooled with, blocked off, ect. There are also small welds on what appears to be factory "blockhugger" style headers, which look like a factory air inj was blocked off.
I also can't see an O2 sensor(on a crappy, pinched, poorly fabbed dual exhaust), which makes me think already a LOT of ham handed goobering has been going on.

I can't decide if I should stash her correct carb, intake, and early 80's garbledeegook in a box for posterity, and buy an intake, distributor, or (?) ?
OR should I go through everything on a vette that is nowhere near starting to climb in value, buy a $500 calibrated overhauled ECM quad, sift through all the hoses, maybe buy an ECM... still relying on 40 year old wiring that seems like is garbage somewhere anyway?? UHG. the late 70's-late 80's were such a crappy time for American cars. ESP ones that have already been goobered with.

No hurry, she is willing to spend some money to get it to drive RELIABLY when she wants. But she is a single mother, and she can't dump 10K into a half carb, half electronic, and a car that is among least expensive 'vettes out there. If it were MY car, I would gut it entirely, rewire the entire car, modern gauges, and put port FI on it. But it's not.

To vindicate myself and my skill set for all the confused newb questions, pics of two motors in my fleet(I own 6 rtr insured vehicles).

I also was a crew chief on 100,000HP F-15E strike eagles in the 335thFS. So even top fuel dragsters seem adorable to me. haha

Thanks in advance for your advice and input. For Angela too haha





Isuzu 4FB1 in my CJ5.


440 in our '58 Fireflite

 

I think most would agree, put all that 81 junk in a box.
2 ways to deal with it. Both mean buying a new distributor. One, get an 80 or earlier carb and earlier HEI. Or two, put a modern EFI conversion setup on it. Lots of us on here done just that.
as per the brakes. Tons of threads on this forum about brakes. Find the leaks. Replace the calipers with lone star calipers and replace the rubber lines.

 

Before you just junk the carb and control system, you need to hear from some folks who actually have an '81 and know what they are talking about.....

 

Getting the thing near stock configuration is going to help if you want to try to fix the 81’s engine management system.

Not having an O2 sensor is a problem. The ECM, distributor and carb all work together. Idle and cruise are regulated by the ECM. There’s a mixture control solenoid in the carburetor that moves up and down by rapidly energizing and de-energizing the solenoid. When the car is at cruise, the mixture control solenoid effectively acts like the power piston in an earlier carburetor, hanging the mixture rods in the primary jets to try to get to a stoichiometric ratio.

At idle, it actually acts like an adjustable air bleed, changing the amount of air coming in.

It relies on the O2 to signal “too rich” or “too lean”. Without that, the computer has no brains for mixture control.

It works pretty well - possibly even better than an M4M quadrajet (75-80), but it needs its brains in place.

If her goal is to have a reliable driver, it’s a good way to go, just requires a little bit of upfront research and learning to get it all working right again.

Is the ECM still hooked up otherwise?

There’s a lot of parts that need to be there for it to work... if they’re more gone than not, it may be better to cut your losses.

Is it an auto or a stick? If it’s a stick, you can pretty easily convert to a mechanical QJet and distributor by unbolting what’s on there and bolting on an off the shelf vacuum advance distributor and sourcing a QJet (not easy, but doable). It MAY be cheaper to fix what you’ve got in front of you though, depending on how much is gone.

Do you have a service manual? Can you inventory how much of the engine management controls are still there?

 

You are in the same state, but still a good drive to Charlotte, NC. If that's not too far, you may want to look up @DUB, a formerly very active Forum member who has a Corvette shop there. Contact info in this thread:
https://www.corvetteforum.com/forums...questions.html

I would otherwise suggest ditching all of the 81-specific stuff and convert to 4-wire HEI and Q-Jet. But what do I know? I went way out of my way to buy an 80 (NOT an 81), specifically to avoid all of this, so I'm apparently unqualified to offer my opinions.

 

Have you scanned the computer for error codes? You don't mention it in your post.

 

I appreciate the inputs and opinions, ALL of 'em.

Shark, I know that hoses have been Bubba'd. The vacuum and electronic bits all seem there.

I DID forget to mention it IS an auto trans. So converter lockup to consider as well!!
Yes. The ECM is still connected. However, I have not looked into the electrical problem yet either. I am hoping the electrical problem has nothing to do with the ECM.
I will get the front up, and look harder for an O2 sensor.

I want to change her oil anyways. Valve covers are leaking too. And wires and plugs and all oils... GAH.

I have seen '81 specific ecm controlled quad's for sale that would be "correct" but not the original. Maybe the best thing to do, considering the converter lockup, and the work involved to simplify the carb and ignition. Throw the numbers correct in a box.

But I have to admit, I am a bit worried I will spend a bunch of her money staying "correct" and still have a bunch of electrical issues and other crap to "learn", on a finicky, fairly complicated early ecm car( ECM plugs. That's a fair amount of wires and car has electrical issues) that isn't mine.

SO IF I were to call for a "correct" bolt on replacement, who would you recommend? Prefer a carb shop recommendation if possible. I hate paying for "oh you own this so your gunna PAY" gouging and markup.

I AM google'ing the snot out of everything, so ya all know I am not trying to be demanding 100% spoon feeding me info.
There is so much to sift through.

IF you disagree with my assessment, what would your approach be? What carb, dizzy/module, handle the lockup, and maybe a few threads to read could you recommend?


Thanks again all

 

Oh. One LAST quick question:
when I took the top off for inspection and to blow out the fuel circuits, there is an @ 1/2" long spring, @ 1/4" diameter, fairly thick wire, I can't recall (and don't remember pulling it out) where it goes. I can't find it on ANY Quad diagrams. Can someone direct me where it should be? It is NOT the solinoid return spring.
Slightly bigger diameter that the TPS plastic rod. Does it seat the TPS unit in the body?

I need to put this back together while I sort out how to handle this. Thanks again all.

Your help has started to change my opinion about 'vette owners haha

 

I will not defend the 81' system.....I don't own one but have worked on them many times and they are troublesome when the car is neglected and Bubba has had his hand in there. Just to start.....anything can be fixed, but the question is why?
The 81' CCC does exactly two things......it controls the idle mixture via a solenoid, and controls ignition timing (and not well). It does not do anything else. I will not mess with the system if it is glitchy as it is just not worth it. There are some die hards that want to argue about not changing things but what are you really changing? Carb and Distributor.....that's it.....and then you can forget about ever having to mess with the system again because there is zero benefit to it. Zero. Every 1981 GM car was equipped with this system and a good portion of them failed.
Checking battery charge after running is not a way to test for draw.....putting a meter on the battery running will show if the alternator is charging...and putting a test light in series of an unhooked battery cable when the car is not running will test for a draw. If the battery has 14 volts running then forget about a draw.......it simply can't. If your test light lights up in series with the engine off then there is a draw.
The fuse box is way up under the dash on the drivers side.
If it were my car, or if you brought it to me, it would get a GM Performance pre-curved distributor, and one of the several Q-Jets I now have on the shelf......it would also get a 2101 Performer,1204 Fel Pro intake gaskets, and long tube headers......and it would put it comparable to a pre-75 spec.....and will run great, reliably for years.......
If you have an 81' that is super nice and never been molested.....that is different......maybe it can be repaired, but if the system is compromised......toss it in the round file.
And for the skeptics......you will never get a CCC distributor to have a curve like a properly sorted HEI like the GM Performance unit.....which is used on the ZZ crate engines.
And if you want to listen to someone who defends these systems....you can do that too.....your choice......it is an add on system that was implemented to pass emissions for the worst year in automotive history. Period.
Early Turbo 350's did not have lockup so it will not hurt anything to not have it hooked up.

Jebby

 

Thanks Jebby!!
Thanks for the fuse tip, and input!!
I am having a hard time swallowing dumping so much TIME and someone else's money ($500 for a bastard half assed ecm carb??) when I will probably STILL have to chase other issues, and have LOTS of repairs yet to do.

If it WERE MY car, things would be way different in my approach. But I'd almost guarantee port FI.

Saving grace is she paid a whopping $2500 for a car she drove home. NICE paint and MINT interior.
NOT the $16,500 the lot was asking. HAHAHA

What about the converter lockup? Is that a myth on these cars as well?

 

While I have no personal experience with an '81 ECM carb for a Corvette, I do have personal experience with both an '82 and an '85 ECM carb, as I had GM cars of those years, which had the electronic feedback carbs. The major stumbling block, so to speak, with those carbs was in their set-up, which required an electrical "jumper" to set the idle speed, via the throttle position sensor, and an old fashioned dwell meter, to set the mixture control solenoid. Otherwise, they are "rebuilt" in a similar manner to a "regular" Q-Jet.

Since we're discussing a 40 year old carb, finding one of the "electrical jumpers" might not be easy. I got mine through a Corvette supply house, I think, and the other electrical items, if needed, may be available from them, also.

 

Not sure what you mean about myth.....but the trans is no different than the millions of TH350's that came before it save for the lockup feature......it IS nice to have....on my old 82 CFI Z/28....when I converted it to carb....I ran a toggle switch for highway driving.....it got about 3-4 MPG better with the lockup......but you HAVE to turn it off during stop and go.....kind of a PITA. There are several ways to enable the function.....one being a vacuum switch.......I am going to try this as after 12 years, I am getting the Z/28 back for my wife

Jebby

 

Vacuum switch like what’s on a 1980 works good all ran through the brake switch . Lockup is a nice feature

 

I agree with Jebby. Remove the original carb, disributor and CCC computer. Get a HEI dist. and either a QJet or Edelbrock, Holley carb. With the Eddy or Holley you will need a square bore manifold, easy to find. And yeah, ditch the factory 'headers' and go with long tube. Lots of crap you can get rid of and make it much more simple and easy to work on. I did all this to mine because it was in a similar condition. Actually $2500 for a driving 81 with a nice interior is a pretty good deal. Pics?

Jim

 

Ohh boy.
To set the idle properly on a replacement, jumper-ing crap and a dwell meter(which I do have btw)?? MORE dead end **** to bother learning on a one year only car, with excessive fiddly bits and gremlins lurking everywhere?

THANK YOU for that CRUCIAL bit of knowledge that I had a scary gut feeling was lurking somewhere to bite ME and my friend HARD. Aside from 40 year old wiring and all the other repairs, ect...

THAT SEALS THE DEAL. Retrofit. I love when my gut instinct about an unfamiliar mechanical/electrical object is correct.

Looks like my main concern will be research Vacuum routing for cruise, headlights, and a vac switch for the trans lockup(wiring and vac routing), and correct carb throttle bellcrank for the throttle, kickdown, and cruise.

If anyone has a great build thread to suggest I study. I appreciate the "hand holding" and will take the on point direction and part numbers, diagrams. But I don't want to be one of "those people".

After all the help, I might have to build a vette. Ya smashing my perceptions of 'vette guys being "Guy DeLuxe" douches. Maybe it's the carbed guys that are cool haha

 

So learning more crap, jumpering wires and using a dwell(which I have), on a one year specific car, potentially with more gremlins and garbage to sort, and the required repairs. That seals the deal. RETROFIT.

Eric, So you are using the brake "hot" side for the electrical input on vacuum switch? With electric switched to trans lockup? What "vacuum switch" did you use? Is it an actual lockup switch for converter on the 1980?

Jim, I'll post a few pics today or tomorrow. AND after the retrofit.

THRILLED I get to "play" and make her pretty!! AND make it so ANYONE with any knowledge and skill can EASILY tune it up.

You guys are changing my impression about 'vette owners. Maybe it's the carbed vette guys that are chill, decent ppl? haha

Just might have to build one for myself you guys keep this up.

 

If you do not like 'electrical things' and have no interest in keeping the '81 engine in original condition, you might be better off to remove and replace the distributor and carburetor (special items that will ONLY work with the '81 engine management system); eliminate the throttle position sensor (TPS), oxygen sensor (O2), and ECM; and use the controls wiring harness for linking with the transmission lockup clutch ONLY. Since fuel economy and performance will be a non-issue, just stick an auto parts store Edelbrock carb (spread-bore configuration) and a GM HEI distributor on it and call it a day....

 

Does it need smog inspection?

 

Another question that may lead the plan’s direction - what are the owner’s overall goals with the car?

Regarding carbs, I’d avoid Edelbrock Carter AFB carbs myself - they’re the oldest designed carb of those well circulated on the market today. I have a personal preference for Q-Jets, many people prefer Holleys and they do have a spread bore model intended for late 70’s GM cars. One of our forum membes (JB78-L82) is very fond of it.

If “performance” is a goal and smog is not a concern, then I’d completely sidestep the CCC system, and start heading down that path.

On that note, if performance is NOT a goal, I wouldn’t mess with long-tube headers. I love mine, and they really enhanced the power output of the car back when it was stock. I’m sure they’re a big gain on my current setup, but I have never tried it with manifolds.

 

This is the first question that needs to be answered. I removed all the smog gear from my '81. That cleans up the engine bay and removes about a mile of vacuum hoses and all the associated problems. If you have that option, do that first.

I purchased mine late last year and had similar issues. There's a camp here that hates the electronic carb but I listened to my gut and glad that I did. The PO had swapped in a 37 amp alternator where an 85 amp is required (I can't ask him why- he died a year before I got his car). That burned out the computer so the carb went full rich. That clogged the single catalytic convertor. Car barely ran so I got it for cheap. Critical parts to for me to fix this:

• Factory service manual, about $35.
• New 85 amp Duralast alternator from Autozone about $100
• Rebuilt ECM from Autozone $82. Reuse the old PROM.
• Rebuild kit for the carb about $60.
• Custom exhaust work to exchange the cat for an X ipie and achieve a true dual system instead of the stupid Y to Y, about $250. I still have the factor stainless steel headers and mufflers.
• Threaded plugs for the air tubes on the original headers.

The check engine light gives you diagnostic codes and it's an easy system to figure out when you go through the manual.

Now my car idles nicely and runs great. The ECM controls the carb, the advance in the distributor, and the torque convertor lockup. The CCC is actually a simple system and for me, wanting a cruiser, was my best option.

The '81 has been maligned because of the ECM controlled carb. My guess why is that old school guys have a problem with electronics. To me, along with some other trivia, it makes this year unique.