MY85Z28

I have a B&M 144 supercharger to install on my 350 CID engine. I don't want it to run lean. After hooking up the monitor, the airfuel ratio during warm up is good ~ 13.5:1. After it warms up and goes to closed loop, the CCC gets very conservative with gas. The carb has a marine accelerator pump and B hanger and CC secondary rods. It has original 57U primary rods.It starts at 13.5 the for a split second during acceleration it goes to 15. then the secondaries kick in and back to ~14. Also when I cruise with light to no accelerator pedal pressure the fuel air ratio goes to 15 again. The car runs great. The air valve opens all the way and spring pressure is set to 0. Obviously if I were on the track I would disconnect the O2 sensor wire to the CCC carb to go to open loop. But can I adjust the carb or do I need to burn the EPROM to change the fuel mix and spark advance table to keep from detonating the engine.

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Jester

My advice would be not not even begin to try to make a CC carb/dist work with a roots blower. Holley makes a line of carbs now specifically set up for blower applications, pick up one of those and a mech. advance dist.

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FastBroker

I'm with Jester, or switch to OEM TBI. Having control over spark with a blower, though, is PRICELESS so try and keep esc if you have the time and money... Otherwise, do the Jester thing and it will be turn-key forever...

Ed Maher

Well all you're seeing is CCCS working. No matter what you adjust at part throttle it will always shoot for stoichometry (sp?) There is nothing you can do about that, thats what closed loop does. At part throttle you shouldn't have any detonation problems.
Once you're past about half throttle you're in open loop anyway. Just for giggles i'd increase the MCS travel to 5/32 or 6/32. That'll make your mid-range mid-throttle a little fatter.
Past that, you might want to think about an adjustable timing control. Either a BTM, or a straight adjustable initial style.
As for burning your own chips to custom taylor a spark curve, unfortunately from what i hear none of the common prom editing software has any bins for where the spark tables, etc are. Thats why i suggest using an aftermarket timing control.

it'll be interesting to see how it works out. In the end you might want to switch to a mechanical carb and distributor for max performance, but then again, maybe not.
...ed
ps. There would be no point in disconnecting the O2 sensor. CCCS is always in open loop above half throttle, so disabling the O2 (or anything else) really doesn't serve any purpose.

MY85Z28

Ed thanks for answering the post. Sure I could ditch the CCC for a Holley till emissions inspection time. Sure, I could get worse MPG. But I like the original carb with 20 + MPG. Timing would solve the major hurdle of preventing detonation. I wish the EPROM board guys would take an interest in carbs just for laughs. But ,I could use an aftermarket adjustable timing control unit that would not interfer with the ECM? I would like to keep the car street/smog legal as it's been my daily driver for 16 years! I was thinking of hooking up a dwell meter at increasing RPMs to see roughly what the spark curve looks like and determine if its even a problem. Maybe the ZZ4 retro-fit ECM/EPROM has a different timing curve, wouldn't it be more retarded?

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Ed Maher

No, you wouldn't have any problems with the computer if you put a BTM or some other timing retard control on it.
As for the PROM, it's hard to say what would have the best spark curve. I agree it does suck that nobody seems interested in at least finding the spark curves for a CCCS. With a blower car though, an LG4 chip might be your best bet with it's anemic spark curve. Since it's not too aggressive you might even be able to run with no retard. At worst, i'd try running a little extra advance, and then use a BTM to retard it under load. Experimenting like that is really all you can do.
...ed