i just bought an '81 vette and i would love to leave it all stock, but i'm having a little trouble with the carburator, the engine is not working at 100% and sometimes it have detonations, don't know how to tune it since it have the ccc, and i'm not sure if the egr is working ,it doesnt have the AIR pump nor the catalytic converter. so i was wondering what things can i eliminate to make the engine work just fine. is it better if i eliminate the computer and go for another carb that doesnt need computer??

 

I have an '81 and love the CCC system. Alot of people would advise you to get rid of it, but here are the advantages of keeping it:
1. It is a relatively simple system to get working properly, in spite of what you may hear.
2. It will automatically maintain the ideal 14.7:1 A/F ratio during normal driving, and allow a richer performance mixture during WOT operation. I have mine tuned to get great gas milage and still make my teenage son salivate when I punch it.
3. It will automatically advance your timing to the point of detonation and back it off slightly if detonation occurs.
It is surprising that you are experiencing detonation at all. Warm the engine up to normal operating temp, then unplug the large 4 pin connector on the distributor and set initial timing between 6 btdc (factory setting) and 10 btdc (I think this gives a little more ompf). Then re-connect the 4 pin plug. If you still have detonation, try a higher grade fuel.
I do not have EGR, AIR or cat on mine and have no problems.
Hope this helps, if you need more advise or have other problems, don't hesitate to ask, I love helping out a fellow '81er. God bless, Sensei

 

all good info. Check all the normal suspects, be sure of the plugs, fuel filter plug wires, dist cap, rotor. A good tune on the carb is a good idea, aquire an 81 Shop Manual. Contact Lars, he has a good carb tuning, timing paper on this subject, will have to swag a bit because of the ECM, thats not addressed in Lars paper. If the heat riser valve is still there make sure its not closed. the shop manual has the testing procedures for all the EGR components. All the sensors will need to be tested, but thats not all that hard. Of course go thru all the vacume lines and make sure there are no leaks..

good luck

 

I agree with both of the above posts. With a little extra effort, the system works fine.

 

That's exactly why most of us who are looking to improve, ditch the 'puter. He can't tell what the hell is going on with it.

Dude.....ditch the 'puter, carb, distrib., smog, and you can work on your own vehicle.

 

well i think i'm going to get the shop manual and will check for vacuum leaks, and ditch the egr and see what happens, thanks!! any other advise is welcome

 

Check if the confuser has stored any error codes (a BIG advantage of the computer is that it can sometimes tell you what the problem is, or at least point you in the right direction).
As well as checking/changing plugs, leads, air filter, etc, don'tforget the O2 sensor. If that is old & tired (or contaminated) all sorts of bad running will occur. Also, don't forget Bubba, he can wreak havoc with an L81! A shop manual is a very good start, but the book on Q-jets by Doug Roe has a section on the E4ME which, when read in conjunction with the shop manual, will explain what's going on with the carb.
If the AIR pump & cat are missing then I'm guessing that you can legally remove the EGR? I'd pull it all off as it's just another (old) system that can play up & make it run bad. Make sure that whoever removed the AIR system has plugged all the vacuum ports & not left anything open. Does the Check Engine light flash at you while driving?Does it illuminate when you turn on the ign?

 

I agree with Paul, he is a pretty sharp guy. Make sure the EGR is hosed befor dumping it. It does do a little good and doesn't cost HP and is not a complicated system. Basically it only works during hiway operation and is inabled/disabled by the ECM. Pull the EGR off, clean it and test it. If it worke, leave it on. If not you will need to plug the hole in the manifold.

 

i called the old owner to ask him some stuff and he told me that he gave that corvette to some mechanic and tried to read the codes from the computer but when he tried to do it, the computer started to smell like if something was burning. maybe thats the problem right?? before the call i changed the coolant sensor and the oxigen sensor.

 

A pretty simple way to check if your computer is dead is as follows:

Turn your ignition on but do not start the car.
Under your ashtray you will find a plug with six(I think) slots.
With a paperclip or screwdriver, jump the two adjacent slots that look like they could be connected (no divider).
You should hear clicking noises coming from the carb. (the solenoid cycling).

If you do, the system is still working. If you don't, it isn't proof that it's fried, but it is an indicator.

 

ok i'm going to try it tomorrow, but something i forgot to tell you is that i always hear a solenoid cliking, the one that is in front of the map sensor when i turn the key on without starting the engine.

 

Where are you located? On the off chance that you are within driving distance, I have the computer interface that will talk to your computer ands see what is going on. I picked it up on ebay for $25 (OTC Monitor 2000). When I decided I wanted the computer analizer, I started looking on ebay. It took about 2 weeks to find one. It's been a great investment. If the computer is damaged, don't worry, you can pick them up cheap from all the people who listen to MsVetteMan and take them out! (ebay rules!) God bless, Sensei

 

lol.....how's that stock 190hp computer controlled motor running? Hey man, that's fine if you want to keep it stock, and you can figure it out.

Care to line up?

Paul is one of the few that has semi figured out the 'puter, so listen to him, he does know what he's talking about.

Oh.......my 'puter is still there, just learned how to unhook it........unplug........gone.....bye.... ..

and......keep driving like grandma if you like with the stock motor setup..........I'm here to say that almost 400 hp beats that crap any day. Hey, but I guess you can look at the other side. Good gas mileage, and a smooth dependable driver right? That's why you bought a sports car right?

 

Hey MsVetteMan, no offense intended . But I've gotta say, I'm pretty sure I'm in the 400 hp ballpark too, with the 'puter still hooked up. God bless, Sensei

 

Wow.......I really must see this setup! If you are being truthful........please divulge the secrets of your sucessful adventure.

I am really interested in how you did this, pm me if you must keep hush, hush.

 

Not much reason to doubt the claim. All the computer does is take the inputs from the sensors (primarily the O2 sensor at that) and vary the amount of time that the mixture rod is more open. At WOT, it is fully open in any case. As I recall from an earlier Lars post, the stock Q-jet is quite capable of supporting 400 HP.

 

The "solenoid" clicking near the map sensor sounds odd Is it on the metal bracket fixed to the top of firewall in front of the driver? All I can remember being there is the AIR system relay and the........ EGR/TCC relay. I think the computer uses the one relay to control both the EGR system & the TCC lockup (I'm guessing that the conditions for allowing both EGR operation & TCC lockup are identical, so the one relay enables/disables both. Not sure though as mine didn't have EGR hooked up so I never worried about how it worked). The fact that it's clicking (if it is that) should point to something, especially with the EGS system still hooked up, though a computer smelling of smoke doesn't sound promising!
Plenty of previous forum members have modified their L81 engines for more than I have & still had the computers hooked up & controlling the brew. Sure, they can be a real pig to sort out when they play up (or one of the peripheral systems does), but they can also highlight faults that you may not even be aware of AND point to the system that's more than likely the culprit. I picked up most of what I know from previous forum members who had modified their L81's (there's plenty of real dumb questions from me back in the archives!). According to Summit I should be looking at 400hp at the crank if I fit TFS heads. AFR tech gave a figure of 410hp with their 180's & Gator81 is probably in the 350hp (gross) ballpark with his engine (obviously I take hp claims from people trying to sell heads with a pinch of salt, but even if grossly over-estimated it'll still have a lot more than 190hp. I just wish I had the cash to buy some & find out!). Besides, I think the L81 gets a lot of unfair criticism regarding power. It has more power than any L48 going back to the dismal low of 165hp in the mid 70's, yet it's got not a bad torque figure, which is at max at low revs (somewhere around 2000rpm?). As hp depends on torque vs revs (I think?) then decent figures should be available if the engine is allowed to breath & produce it's power at higher revs (which is the same problem all smog engines suffered from in the 70's - you should see what Federal emission laws did to the poor engine of my bike when it was stock!). Another advantage is that the L81 is a lot lighter than the earlier smog models (& the '82) so we've immediately got a better power/weight ratio to start from. Ha!
Once those secondaries open up the E4ME behaves like a std Q-jet in that the mixture is mechanically controlled by the secondaries, with the primaries running at full rich. Ign timing is advanced & you can set the full advance position, just as you can set it with springs & weights in traditional systems. There's not a lot of difference, although you can't control what the advance curve looks like (though I've not had a problem with it. Unlike the problems I've had with other things with curves that I can think of ). The problems start when you want a cam that gives low manifold vacuum (which is the point at which you kiss the computer goodbye), or when a sensor, or circuit, goes bad (which is when you start scratching your head in confusion: I find that beer helps ).

For diagnosing your car then definitely get the shop manual for the year. It's not cheap when compared to other manuals, but is light years ahead of all of them combined. Even if you end up scrapping the computer control the manual is still worth buying as there are some differences with the '81 that most other manuals don't mention. It reaches the parts that other manuals don't reach!

 

I had someone pm me to ask the same question and I sent them this:

Basically, if you build a 400 hp motor, the CCC system will support it. I set my base timing about 10 BTDC instead of 6, changed the secondary metering rods and cut off the secondary air valve stop on the carb to allow it to open fully and flow more fuel and air (if you need more detail on this, let me know), and put in a Hyperchip and an MSD 6a box. I'm not even sure the Hyperchip was needed, but I'm sure I felt a difference in the seat of my imagination! I don't have the EGR or AIR or cat. Other than these mods that are related to the CCC system, I've just done the standard stuff; exhaust, heads, intake, cam etc.

In addition to this, I have done a few other mods to the carb per Doug Roe's book: drive in the air bleeds, perforate the secondary pick up tubes, etc. These don't really effect hp, so much as allowing me to set the secondary air valve at 0 tension without bogging for quicker response. God bless, Sensei

 

Sensei,
I'd read some real bad feedback on the Hypertech chip so decided not to spend any cash on one & use it for something else. I fitted a new cam (crane 210/216, .440"/.454" 114lsa) & intake & was disappointed to find that I'd lost some of the low end grunt. Shortly after I fitted a Hypertech chip I bought from somebody on the forum & a lot of the low end grunt felt like it came back Maybe I imagined it as I've read that the chip only affects WOT, but it certainly felt a lot better after fitting it. I then advanced the base timing to 11*BTDC (Hypertech said a max of 13 could be used, but I erred on the side of caution due to some stations selling poor gas) & that improved throttle response, pick up & gave even more low end grunt back. My conclusion is that the chip has done something positive on my slightly modified motor (still running the stock heads & CR), but maybe they don't do anything for stock systems??

 

i did the test and there was no sound coming from the carb, can the motor be able to run even if the computer is not working??.
P.S. the solenoid that i hear clicking is the egr/tcc solenoid