The engine in my 94 Z28 has just been rebuilt. I elected to go with a LT4 Hotcam kit and LT headers. The mechanic called to say the car is ready but running very rich. He even suggested I have it towed home until I could get the CPU reprogrammed. I was under the assumption that the car should run fine with this combo using a stock CPU? Does it need to "learn" by running or should I go ahead and have the CPU reprogrammed to handle the new setup?

Thanks!

 

Do you have any more details of your setup. Did you have bigger injectors put in by chance? The Hotcam is one of those cams that can be put in but doesn't require immediate tuning. I would hope the mechanic that did the work could investigate the problem a little further because if the car is running too rich, it may be very damaging to the motor.

 

Thanks for the reply, I went back with a Racetronix fuel pump, and 24lb SVO injectors. Still has the stock Throttle body. The mechanic said one of the O2 sensors might be bad. IT is also fouling the plugs pretty bad.

 

I also have the LT4 hot cam, but had the full kit installed. As part of the conversion, I had the computer reprogrammed and have never had a problem

 

Get the computer reprogrammed. A mail order tune is cheap and will be pretty accurate for a hotcam.

 

I think the SVO's are what casuing the Rich condition. At our fuel pressure, there rated higher than what they are. I think the 24 svo's are more like 25's or 26's. Somebody will conform that

 

The stock injectors are programmed for 24.9#/HR. Correcting the SVO's to 43.5psi increases the flow by 5%......24 x 1.05 = 25.2#/HR. Not a big enough difference worth worrying about.

 

Thanks guys, I'll get new 02 sensors, reprogram the CPU and see how it goes.

 

Are you running the car with open headers? Are the headers coated (possibly damaging the O2's when the initial coating burnoff occurred)? Any way you could get a log of the car? How did the 'mechanic' (which sometimes I hate calling them) determine that one O2 MIGHT be bad?

 

My driver side O2 sensor was bad and caused my car to run VERY rich, which i was informed was because of the hotcam kit (and not being tuned to it) so i waited a while to get the mail-order tune. finally put the new pcm in and it ran a little better, replaced the 02 sensor after that and it ran perfect

-Chris

 

I have a similar cam (CC305) running on a stock tune. You might want to check for header leaks, I had one leaking primary that caused my car to run rich. Your car should NOT foul plugs, I just changed my plugs after a couple of summers on the heads and cam setup and every one is burning perfect that I replaced. It will run a little rich down low on stock tune but should NOT foul plugs. Other buddy has a similar setup to ours and he is running stock tune also with success. I would think the SVO's were causing it to run rich but I would go with Injuneer on that call as hes seems most knowledgeable about these cars.
Josh

 

Again thanks guys, some useful info there... the headers are not open and are used so the coating is probably burnt off. I'm not sure how the guy determined an O2 was bad? I'll find out today when I drop by to pick up the car. I'll check for a header leak as well. Anyone know where I can get O2 sensors for Hooker LT headers?

 

It'll be the same O2 sensor that came in the car from the factory.

 

I was thinking it might need one with a longer wire but then I found some O2 wire extenders. The sensor in question came with the used headers and may have a "home job" done on the wire.