To computer or not to computer

[69hurstolds]

This is all really helpful information. It's a pretty far from stock 1972 Olds 350 that I've built to a little more aggressive than factory 1970 W31 specs but it's going to my 1982 Cutlass. Though I'm young I've never really learned anything when it came to the emissions computer and all that stuff because I only ever learned on my Grandpa's 1972 Oldsmobile Vista Cruiser that he drag raced, he was a hell of a man but up until he passed in September he still couldn't decide if he liked a Quadrajet or Holley better. Sorry if I caused any irritation to anyone, I just needed some guidance on something I didn't understand.

Your setup probably wouldn't like the ECM setup. CCC was designed to keep the car in "optimum tune", or close to it, to ensure emissions control and fuel economy were maximized without much regard to performance. Your engine build, if it's more aggressive than W-31 specs, is far from emissions/fuel economy. Can you modify a computer feedback system for performance? Sure. Look around today at 707 HP Challengers as just one example...

CCC systems are somewhat cryptic system, but also many claim it's very basic (which it is, yet there are many who STILL can't figure it out), but also were the first step on the ladder to where we are now with computer controls. The thing is, once you do learn it and figure out how the system works, it's not that hard to live with and keep your stock car running well. But you have to manage your expectations.

There's really only two ways to go, either CCC, or not. You can't just disable some of the system and have it work the way it's supposed to. It's pretty much all or nothing. True, there are a couple things you could do without totally screwing up the CCC system like removing the A.I.R. system components, but for the most part, you can't modify it too much without making the car run like poop.

When it comes to carb choices, Holleys are fantastic competition carbs and pretty easy to modify. But IMO, nothing beats a well-tuned Q-jet on the street for all-around performance and economy. Street manners and performance as well. If it wasn't a good idea for the street, then Holley and Carter wouldn't have bothered to make their own spread-bore carbs. Each has their good and bad points.

 

[Bonnewagon]

OK so a '72 350 into an '82 Cutlass. Perfect, just do it. Keep everyhting as is and it should slip right in like it was born there. That is a good low compression engine that will motivate that Cutlass like never before. I agree with 69hurtsolds that the best carb is the world is the Q-jet that came with it from the factory. It will work with lots of engine modifications as is. But if you have a good running Holley or other fine brand carb already stay with it. All the CCC stuff can be junked. Even the T-350-C trans could be retained by just using a dash mounted switch to engage the lockup converter. That is good for 3 or 4 hundred rpm at highway speed.

 

[Clone TIE Pilot]

Another thing about CCC systems ix that they have 4 modes, cold engine mode called open loop, warm engine mode called closed loop, lean cruise mode around idle and mid throttle, and power mode at WOT. The computer only controls the fuel mixture on the primary side of the carb during idle and cruise. At WOT the compuuter goes full rich and is pretty much just a plain mechanical carb at high throttle openings, this is the power mode. This means you can still dial in WOT performance with secondary rod changes.

The stock idle circuits in CCC Qjets are border line lean from the factory and can be enlarged a little for better idle control, even for bone stock engines. You can also bump the base ignition timing a couple of degrees without affecting the computer. There is also the heated O2 sensor upgrade for improved operation. Sadly the Olds version of CCC has very limited selection of PROM chips for tuning. Chevy has hotter PROM chips available to work with hotter cams than Olds.

 

[Bonnewagon]

Another little known trick is to punch out the plugs that cover the idle mixture screws. It is verboten on cars that must pass emissions tests- BUT- if you are exempt you can really improve the idle smoothness. I had a friend with a MCSS that had just a horrible idle. He was from Florida so no test. I adjusted those screws until the idle smoothed out beautifully. He probably had other issues but needed to drive from NY to Florida and just wanted it to stop shaking so badly at red lights.

 

[69hurstolds]

Another little known trick is to punch out the plugs that cover the idle mixture screws. It is verboten on cars that must pass emissions tests- BUT- if you are exempt you can really improve the idle smoothness. I had a friend with a MCSS that had just a horrible idle. He was from Florida so no test. I adjusted those screws until the idle smoothed out beautifully. He probably had other issues but needed to drive from NY to Florida and just wanted it to stop shaking so badly at red lights.

GM only did that to keep people from messing with them because when CCC was used, it minimized people "winging it" the old-school way, throwing off the calibrations. In fact, removing the caps is a bonafide GM service procedure when working on the carburetor. They even put the "dots" on the baseplate to mark the spots to chisel. If a state says you can't remove the caps, then maybe you should move, you've got bigger problems. So, say if your dealership removed the caps in 1989 and readjusted the carburetor, then you can't pass emissions today? That sounds unreasonable. I guess if you were worried about it, you could dab a little rtv on the surface of the hole and make it look like you can't do anything with them. Then remove the RTV curtain if you have to get back in there.

You really must to be able to adjust those screws if you want to ensure your carb is tuned correctly. It's an important part of the 4-point adjustments on the Monte SS carbs. 442 used a 3 point setup where the idle air bleed valve (IABV) was the brunt of the setting and the factory mixture screw settings weren't quite as critical to be changed, although you still should for proper baseline settings. Those mixture screw holes get filled with steel screw rust and general gunk over the years and can cause issues. You can tell by looking at the top of the IABV for a letter. If no letter, then mixture screws and IABV need to be adjusted to set proper idle mixtures. If you have a letter, then you use the IABV setting tool, set it and you should be fine as long as the factory settings were never messed with and the dwell can be adjusted to spec otherwise. Still need to check it regardless.

 

[olds307 and 403]

As said, ditch the CCC in your case. Get the carb of your choice either built to your specs or you build it. Same goes for tge ignition. When you install it, add a wideband to fine tune it. On my modified 800 cfm Qjet, a few screw turns change AFR alot. What are your engine specs? Good luck.

 

[Bonnewagon]

if your dealership removed the caps in 1989 and readjusted the carburetor, then you can't pass emissions today?

No, I meant the stealership had the capacity to adjust the carburetor, test the exhaust, and maintain the factory emissions standards. The plugs were there to keep Joe Screwdriver from tampering with the mixture screws and upsetting the emissions. That was so long ago that I doubt any stealership still has that equipment let alone a mechanic that knows how to use it. But when the average younger guy looks at a carburetor he has no idea what is behind those plugs nor what they can do. In NY after 25 years you are emissions exempt so using the mixture screws to smooth out your idle is an accepted practice. Back when they tested using the IM240 test where the driving wheels were placed on rollers, the car was run through various speeds, and if anything was out of whack you failed. Pre-computer cars could not pass so that is why the 25 year rule was instituted. In fact many otherwise good running computer cars failed too. It was a sad time for sure.

 

[Clone TIE Pilot]

The base needle screws are the coarse mixture adjustment for both curb idle and off idle mixtures . The idle air bleed valve is the fine mixture adjustment for just the curb idle. CCC Qjet needle screws are very fine metric threads that require a lot of turns for a response. Even stock engines benefit from enlarging the idle tubes and idle discharge ports though its a more involed tuning procedure.

CCC systems are very sensitive to vacuum and exhaust leaks. Worn throttle bushings can cause vac leaks as well as throttle plate misalignments and hangups. Exhaust leaks throw off O2 sensor readings. Base ignition timing also has a large effect on idle quality and even stock engines benefit from more advanced than stock timing settings.

 

[Metzger82]

As said, ditch the CCC in your case. Get the carb of your choice either built to your specs or you build it. Same goes for tge ignition. When you install it, add a wideband to fine tune it. On my modified 800 cfm Qjet, a few screw turns change AFR alot. What are your engine specs? Good luck.

It's a Olds 350
Bore 4.125 (forged flat top pistons) x Stroke 3.385
Olds 1972 7a heads with .010 off the surface with 2.07 intake and 1.71 exhaust versus the stock 1.88 intake and 1.50 exhaust
Oil restricted pushrods
Custom hydraulic flat tappet cam with solid flat tappets and roller rockers
Blueprinted oil pump
Edelbrock Performer RPM intake
Recurved HEI distributor
750 cfm Holley
.... and more I'm forgetting probably