1981 Carb and Computer advice
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Instructor
Joined: Aug 2006
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From: Apple Valley MN
1981 Carb and Computer advice
Last month I purchased a 1981 Coupe with 45,000 and a new paint job after a long search and having to waiting until I put my two children through 4 years of college. Well I made the mistake of trusting the seller who also had a C4 – I know bad idea. It turns out all of the Emissions have been taken out or disconnected. Also – I found out all the electrical hookups on the Carb have been disconnected and the wiring harness missing. It runs a little ruff at idle but performs well. A trusted mechanic recommended replacing the carb with a non Q-Jet carb like a holley and forget about trying to hook up the CCC? My question is this a good idea and should I also replace the Stock Exhaust manifold with a set of headers and true duals while I’m at it? The prior previous Bubba capped the A.I.R. hoses off the Manifold with a bold and a pipe clamp. Note: I did a VIN check after the fact and found it failed emissions in the early 1990’s and was deemed exempt - probably why everything was disconnected.
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
MN81C3,
Yes, its a good idea to replace your carb with a non computer carb, but you also have to replace your distributor. Those are the only two things the computer controls in the 81. I am in the process of doing the same thing to my 81. Just got the engine out last week. True duals are also a good idea.
Yes, its a good idea to replace your carb with a non computer carb, but you also have to replace your distributor. Those are the only two things the computer controls in the 81. I am in the process of doing the same thing to my 81. Just got the engine out last week. True duals are also a good idea.
Melting Slicks
Joined: Mar 2006
Posts: 2,465
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From: Orange Park Fl
Sounds like bubba did a number on you. You will indeed need to either get the CCC system back up or replace the carb and distributor (you will also loose your Torque converter lock up.) If you go the non-computer route, I would stick with a Q-jet not a Holley. The exhaust headers should be okay as long as they are not leaking. There are several of us here on the forum that like the CCC system on our '81s, it is a step up from the non-computer cars. It is reliable and helps maintain optimum performance. The main reason people get rid of it is not because it is a bad system, they are just not comfortable with it. As computer systems go, the '81 CCC system is as simple as they come and it probably would not be hard to get it going again. You say there are wires missing, they were probably just cut in the engine compartment. If the car is running decent, the computer is probably still hooked up and working for the timing (distributor). You may just need a plug (from any computer q-jet at the junk yard) and find the end of the wires for the carb where they were cut off and splice it in. This will probably be easier and almost definately cheaper than replacing the carb and distributor. If you would like to go this route, just let me know and I'll walk you through it. God bless, Sensei
Melting Slicks
Joined: Jan 2005
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From: Madison Ms
Trash the puter if you want power. Keep it if you want a good daily driver/cruiser. Without the puter you will need to replace the carb and distributor as stated earlier. No way you can properly tune a high performance motor with the stock crap on it.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
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From: Boca Raton Florida
If the CCC is actually there Probly what they did was just cut the connectors off. So for $20 you may be able to get it up and running correctly. Spend the bux on go fast parts like a cam and exhaust (duals) There are only 2 connectors on the carb, how hard can it be to fix 4 wires? The advantage is you don't have to be screwing around with modifying all the other stuff that would be needed to completely eliminate the CCC and have everything work.If your not required to do emmisions testing you have all kinds of options with that setup
Thread Starter
Instructor
Joined: Aug 2006
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From: Apple Valley MN
Thanks Sixshooter and Sensei. It sounds like the best thing to do is to try to get the CCC controlling the carb again. The trans shifts through the 4 gears and locks up like it should and the car runs great other than the idle. I have the build manuals and a Chilton’s so I will trace the wires and see what I can find. I will keep you posted.
Melting Slicks
Joined: Mar 2006
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From: Orange Park Fl
Originally Posted by MsVetteMan
Trash the puter if you want power. Keep it if you want a good daily driver/cruiser. Without the puter you will need to replace the carb and distributor as stated earlier. No way you can properly tune a high performance motor with the stock crap on it.
Thread Starter
Instructor
Joined: Aug 2006
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From: Apple Valley MN
I found the carb has the Choke wire attached and i found two open plugs. I found a wire harness on the pass side with 5 plugs all color coded green which I thought were for the missing AIR pump. I also found an open 4 prong plug near the master cyl. Any idea which is which? I can eMail pictures. Haven'g figured out how to attach?
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Pro
Joined: Dec 2000
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From: Camino CA
The 4 prong plug by the brake booster it probably for the distributer. The wiring harness that goes up the passenger side has 2 connectors for the carb, one of those 2 should have 3 plugs, the other has the wires coming out at 90 degrees, 2 2-wire connectors for the smog pump, 1 green testing connector, and a connector with black and yellow wires for a temp sensor in the intake manifold.
Last edited by Ben Taylor; Sep 4, 2006 at 02:06 PM.
Thread Starter
Instructor
Joined: Aug 2006
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From: Apple Valley MN
From what is sound like, then the distributor is not even hooked up? If that is the case, then the CCC may be completly by passed. The Transmisstion shifts through the 4 gears very smoothly but I cannot tell if the Converter is locking up.
I uploaded pictures of the Carb, the Wire Harness i found on the Pass Side and the open 4 prong plub. they are in the Corvette Pictures » C3 Corvette Pictures » C3 Corvette Parts and Mechanicals Photo gallary.
I tried to attach them here.
http://forums.corvetteforum.com/phot..._Fire_Wall.JPG
http://forums.corvetteforum.com/phot...1_wire_h_1.JPG
I uploaded pictures of the Carb, the Wire Harness i found on the Pass Side and the open 4 prong plub. they are in the Corvette Pictures » C3 Corvette Pictures » C3 Corvette Parts and Mechanicals Photo gallary.
I tried to attach them here.
http://forums.corvetteforum.com/phot..._Fire_Wall.JPG
http://forums.corvetteforum.com/phot...1_wire_h_1.JPG
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
OK, looks like its there, all you need is to reconnect it. I'll take a look at mine this evening and tell you what colors go where. Looks like the choke is connected as is the EGR plumbing, so you might not be too far off.
Thanks!
Melting Slicks
Joined: Mar 2006
Posts: 2,465
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From: Orange Park Fl
I'll have to look at mine to be sure but it looks like you still have everything. The 4 pin plug in first link goes to the distributor. The single wire green plug is a test connector that does not plug to anything. The two black plugs go to the carb. 3 pin is the throttle position sensor (left front of carb, white connector), the two pin is the mixture control solenoid (on top of carb at right front, blue connector). I believe the other two plugs are for the smog pump and EGR, which I do not have any more. Plug in the carb and distributor and let us know what happens. God bless, Sensei
Pro
Joined: Dec 2000
Posts: 560
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From: Camino CA
Here's the plug for the distributer
The plugs for the carb / smog pump
I removed my smog pump, but the unconnected 2-wire plugs shown on the bottom both connect to it, they should match the colors on the smog pump if I remember correctly. One is for the pump itself and the other is for the diverter valve. The EGR electronics should be red and yellow and are mounted to the engine near the firewall.
The plugs for the carb / smog pump
I removed my smog pump, but the unconnected 2-wire plugs shown on the bottom both connect to it, they should match the colors on the smog pump if I remember correctly. One is for the pump itself and the other is for the diverter valve. The EGR electronics should be red and yellow and are mounted to the engine near the firewall.
Melting Slicks
Joined: Mar 2006
Posts: 2,465
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From: Orange Park Fl
msvetteman has a point, but when he parts his hair right it's not that noticeable (just kidding). There could well be a problem in the system, but, as I stated earlier, as computers go, the CCC system is as simple as it gets. Hook it up, see what you have, and go from there. People seem to tremble in fear that their ECM has gone bad. That's about the worst case scenario, and replacing it is still cheaper than either a distributor or a carb. God bless, Sensei
Thread Starter
Instructor
Joined: Aug 2006
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From: Apple Valley MN
Thanks all - I will take a look tonight at hooking up the carb. The question i have is the distributor wire? I do not remember seeing a unconnected plug hanging from the distributor - only the open plug. If i cannot find the other end - I assume i can find a replacement locally. I see that Ecklers and CCentral carry them but i have to believe NAPA would carry the replacement. I think it's worth a few dollars to try and get it working. I will keep everyone posted. Thanks again.