If I modify my 81 vette , cam, headers, carb, intake, etc.. Do I have the modifiy my computer or something like that ?

 

i am trying to learn about exactly the same thing becasue i want to do something similar. apparently the 81 computer controls alot of things on your carb including mixture . it controls timing . the computer also controls the loc up converter for fuel economy in 3rd gear. so the computer,carb,dizzy,tranny are all connected. there are a few threads in here with good info on it but everyone has unique set ups so its different for everyone. apparently most people just change carb and dizzy. hook up a modification for the loc up converter and get rid of the computer all together !

am i on the right track ??

 

The computer controls Fuel Mix and timing only on the engine. You can make those changes you posted and keep the distributor and carb with the computer. You may need to change the secondary jets and/or rods to get it dialled in, but the primary side should be ok. With the new exhaust be sure and get the bung welded in for the O2 sensor as close to the exhaust collector as possible.

 

Main thing is you just have to choose your parts a little more carefully. Pick a cam that has enough vacuum to not make the computer angry and any spreadbore intake with an EGR place should work fine. As sixfooter said, make sure to put an O2 bung as close to the collector as possible, for the exhaust. If your CCC system is working like it should, it's really not too bad to keep working. Only reason I went away from mine is because it wasn't working and I didn't feel like tracking down all of the crap that was wrong. Instead I just got a late model non-computerized q-jet (Edelbrock 1904) and a regular HEI distributor and said to hell with the computer.

Now with all the tuning crap I have to do, I almost miss my ccc system.

 

Mine has a 2101 Edlebrock intake on it from the factory and its a pretty good unit, if thats what you have I would stay with it until you see where you are performance wise.
I have a Crane cam kit from summit I am installing this week CRN-114132. I am also installing an Air Gap intake, but thats not necessary and I have block hugger ceramic coated headers going on with 2 1/2" exhaust I have yet to build. That should round out the week, and maybe next week too

 

Sounds like you're doing exactly what he wants to do sixfooter. Y'all should keep in touch via PMs as you make progress.

Now if I could find someone building a 427 small block that's built to run on low octane...

 

If you change the carb and distributor. You can do what ever you want.

 

So, I if want to keep the computer, I can only change the intake, cam and the headers... but for the headers, I have to modify them for the O2 sensor... I going top keep the car like that.. to slow...

 

You can use different heads with the computer, too. You just don't want to go with too radical of a setup because the computer is very basic and won't know what to do with a huge lumpy cam or something like that. All it does is read the sensors and adjust the mixture accordingly.

 

If your not changing heads I would keep the aluminum intake that came with it. A cam change and headers will give you a pretty good bump with the computer.

Just to give you an idea, that carb is a 650 or 750. The computer, carb and distributor can support a 300 to 400 hp motor. I am keeping them, installing cam, headers AFR180 heads and an airgap intake, my target is about 350hp.

 

All depends how much money you want to spend. I have an 81, last year i did the same thing. Wanted little more hp so I went to non comp carb and mallory HEI dist. Unhooked the computer except for the converter lock up. Already had true 2 1/2 duel exhaust into flow masters. But it was still lame. Here is what I just did, 357 short block, RHS heads,comp cam with chain and sprockets, power plus intake, new lifters push rods and roller rockers, tall valve covers. Then I install a pair of patriot side pipes. I did all the work myself and cost about 3k. What a car now.

 

Okay, here's the real deal from someone who drives the proof every day. The '81 CCC system will support just about any amount of performance mods you would make on a street driven car. For the engine, it brings in the timing advance based on vacuum and engine RPM and uses the O2 sensor to adjust the fuel mixture for optimum efficiency when cruising and allows the full potential of a 750 cfm Quadrajet during WOT. It in no way limits performance potential.
A lot of guys don't understand the system and are afraid of it, so they throw away hundreds of dollars replacing the carb and distributor with inferior units. The system is easy to diagnose, and even the most severe problems with the CCC system itself would cost less to fix than a cheap HEI replacement distributor.
I am running Dart heads, flat top pistons, a Comp XE 262 cam, headers with 2.5" true duals with no cats, no EGR and no AIR. A MSD 6a box, Edelbrock intake and I'm sure there is more I am forgetting here. The car runs like a scalded dog and gets 18-21 miles per gallon. You gotta love that! God bless, Sensei

 

Looks like we're going to have pretty much the same setup when I get my AFR180s!

Summit sell reducers with O2 bungs already fitted & that's what I did with my Headers. The O2 sensor is further downstream in the exhaust but it doesn't show any signs of not getting up to temp (maybe it's partly due to the ceramic coating on the headers helping to retain heat?).
Here's what I found after doing some mods (fitted a 2040CompuCam (think it's the same cam SIXFOOTER is fitting), Performer 2101 intake, 1.52:1 roller tipped rockers, 1 5/8" headers & true 2 1/2" duals with H pipe, along with a few minor odds 'n' sods): After fitting the cam it felt like there was a reduction in low end power, though the mid-range had picked up a bit. I'm not going to give any impressions of the cam as it's designed to run with a higher CR than the puny stock 8.2:1 that I'm running. What I did was to advance the base ignition timing from 6BTDC to 11BTDC & there was an improvement in low end power, along with better throttle response. As the computer doesn't know crank position it just calculates the advance needed and adds it in assuming that the base timing is 6BTDC. So I've advanced the entire curve by 5*. I was told that it should be safe to go to a max of 13BTDC as a base figure, but I went for 11 for a bit of a safety margin.
I also found somebody on the forum selling a Hypertech chip for an '81 so grabbed it & stuffed it in the computer. It made a slight difference in that the engine felt more "perky" (I guess a dyno may show a slight power increase?), but I doubt very much if the chip would make much difference in a stock setup.
It seems that most popular aftermarket heads work with the CCC system, the problems with the system start when the chosen cam gives a low manifold vacuum at idle (unfortunately I've forgotten the magic number).
A free flowing exhaust is something the system loves, the improvement to mine just from fitting true duals (with stock manifolds) was excellent. As the computer takes care of the primaries there wasn't any need to fiddle with the carb as the secondary mixture seemed OK. What I did find was that the later fitment of Headers leaned out the secondary mixture. After a few emails to Lars I swapped out the stock CH secondary rods for a pair of DA rods. Nice difference With the stock manifolds & true duals the engine pulled well until it got up towards the red line. Then the manifolds became a restriction & power dropped off. Headers solved this, though I didn't notice any improvement in low/mid range due to them. A balance pipe (H or X) is well worth fitting if you go for true duals.
Not sure I felt any difference when I fitted the 2101 intake.
I also fitted a lifter valley baffle plate to help keep hot oil off of the underside of the intake. Even better is the fact that it might stop a lifter popping out if I ever drop a pushrod.
I've still got the cold air intake stuff & a charcoal cannister fitted (but disabled/broken) & the AIR, EGR, cat, etc have long gone. It runs pretty good when compared to stockish L48's & I'm hoping for a big improvement when I throw some AFR heads at it. Anybody got any recomendations for places to get some AFRs?
I wouldn't fit a 160 stat when running the computer. Some people might find it works OK, but a lot have found that it causes the computer to keep going in & out of closed loop as coolant temps are lowered. Mine works well with a 180stat.

gingerbreadman, yes you're on the right track. The computer controls the carb primary side using an O2 sensor in the left exhaust (hoping that both banks of cylinders are running the same!). At WOT, it gives up trying to control stuff & goes full rich (I think?) on the primaries while the secondaries control the mixture in the traditional way. The computer has no input on the secondary mixture, it's all down to jets, needles, etc. It also controls the spark advance by deciding what advance is needed (probably from a lookup table) & adding it in. How it controls the converter lockup is a bit of a mystery because I messed mine up! What it does check is coolant temp (if it's cool/cold then the trans fluid must be cold, so the converter isn't locked up, allowing it to slip & generate heat to warm the fluid). It also uses the VSS (a sensor in the speedo) to check the speed. It doesn't know anything about gears. The reason that lockup doesn't occur in the low gears, I've been told, is that the pressure sensor wired up in series with the TCC solenoid in the trans cuts the circuit if fluid pressures aren't what they'd be if running in top gear.
The one problem I know of when modifying L81's is when a cam is fitted which gives a low manifold vacuum at idle. The computer reads a low vacuum & assumes that it's due to the throttle being slightly open. So it richens up the mixture in the primaries. This causes fuel to puddle in the manifold & when you do open the throttle there's a sudden very rich condition and the motor will stumble.

 

UKPaul sounds like your in the business. I have never ran a pair of AFR heads so I dont know about them. Check out RHS heads. I went with the 64cc 2.02 1.60. I have unhooked just about everything I could. I did notice with the cam I did loose some vacuum at lower RPM. I have my base timing set at 8 and total is about 37. I went to a machine and told him what I wanted and about how many ponies I wanted and he came up with all the parts. All I can say is he nailed it.

 

Thanks, I'll have a look