Is this normal after a cylinder head swap?
Is this normal after a cylinder head swap? FINALLY finished up swapping a set of Livernois Stg 3 heads onto my 2003 Z06. After triple checking everything last night, I started her up and she ran just fine. No bad lights, no leaks, holds 40 PSI oil pressure between 8-900 RPM at idle. I let it run for about ten minutes just to get it up to operating temp. What concerns me is the amount of smoke coming from the engine compartment. Now having had this thing apart numerous times, Im very familiar with the smoke generated as the car heats up and all the oil, coolant, dirt, grime burns off the headers but after that stopped, I still had a good amount of smoke coming from what looked like behind the intake by the firewall. Additionally, the exhaust was red hot from the headers back, see below.....
Ive honestly never looked at the exhaust under the car while it was running, but those cats are glowing red.
Lastly, there was a bit of black smoke puffing out of the exhaust. Im assuming that is largely due to the lack of updated tune yet. I will be making an appointment at Virginia Speed to have them do a full dyno tune. Any thoughts are much appreciated.
Ive honestly never looked at the exhaust under the car while it was running, but those cats are glowing red.
Lastly, there was a bit of black smoke puffing out of the exhaust. Im assuming that is largely due to the lack of updated tune yet. I will be making an appointment at Virginia Speed to have them do a full dyno tune. Any thoughts are much appreciated.
well, the headers arent actually hot, its the catalytic converters and the x pipe. Last time I had a vacuum leak, I had a pretty good stumble when I reved the motor...no indication of a leak at the moment...Ill look into it though. Any other ideas?
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Ok, I got some more time to mess around with it today. I bought an infrared thermometer and fired her up. Started right up and idled with no problems for the better part of 20 minutes. The temps on the header tubes averaged within 20 degrees of each other and the cats were substantially cooler (no reddening) and within 20 degrees of each other.
Everything was looking good until the car suddenly stumbled and stalled. Following that, it would crank but wouldnt fire. I pulled the throttle body to look in the intake, no significant oil so the catch can seems to be working. Then I pulled the spark plugs.....
These were new with the head swap....clearly she's running stupid rich. What I cant figure out is why. I couldn't find any vacuum leaks at the brake booster, vacuum line on the back passenger side of the FAST intake, or around the base of the intake itself. The A/C system works as it should so none of those vacuum lines have leaks. Any other ideas as to where a leak might be would be greatly appreciated. Or any other reason a head swap would suddenly cause it to run excessively rich.
Additionally, I did take off the valve covers to check everything, and all looks good.
Everything was looking good until the car suddenly stumbled and stalled. Following that, it would crank but wouldnt fire. I pulled the throttle body to look in the intake, no significant oil so the catch can seems to be working. Then I pulled the spark plugs.....
These were new with the head swap....clearly she's running stupid rich. What I cant figure out is why. I couldn't find any vacuum leaks at the brake booster, vacuum line on the back passenger side of the FAST intake, or around the base of the intake itself. The A/C system works as it should so none of those vacuum lines have leaks. Any other ideas as to where a leak might be would be greatly appreciated. Or any other reason a head swap would suddenly cause it to run excessively rich.
Additionally, I did take off the valve covers to check everything, and all looks good.
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What cam do you have in the car? Anything with alot of overlap is going to leave alot of unburnt fuel in the exhaust particularly at low RPMs. The thing is that normally that unburnt fuel will just lay in the exhaust (usually in the cats which plugs them up which is why they usually get chopped). Obviously in order for something to burn it needs oxygen, and quite frankly you don't find it in car exhaust (see CO poisoning LOL). What's happened now I bet is that the flow characteristics of the heads have changed so much (much more airflow) and some oxygen (car running lean initially) getting into the system thus burning any of that unburnt fuel in there. So you are probiably wondering why it didn't regulate and correct itself?
Good question. I suspect the parameters of the tune are way way out now with your new heads. Thus, it's wild swing from lean to fat.
Could you maybe have a vacuum leak? Maybe, but not likely IMO. If you had a vacuum leak the car would idle high all the time or just have a hard time idling period.
Good question. I suspect the parameters of the tune are way way out now with your new heads. Thus, it's wild swing from lean to fat.
Could you maybe have a vacuum leak? Maybe, but not likely IMO. If you had a vacuum leak the car would idle high all the time or just have a hard time idling period.
Did you run the car without them on? If the EGT's are that high and the car is not running insanely lean from a vacuum leak there is no other reason that I know of that would cause that. Especially since you mentioned the headers don't glow, only the cats, that is a pretty clear indication that they are clogged IMO. I will be interested to hear what the problem is. I will try and check back sometime to hear about it.
What plugs are those? Obviously a platinum tip, but just curious...the electrodes look tiny...and probably much more prone to fouling (since your tune is off) than, say, a set of NGKs. Just a thought. Personally, I'd change the plugs to a new set of NGKs, start the car just long enough to know that it's running again....and then trailer it to the tuner. Cats HATE excess fuel, as I'm sure you know.
I didnt run it without with cats on, but I did run it a second time for 20 minutes and the cats didnt get hot at all. The plugs are the factory AC Delco units so I may run by the parts store and grab some NGKs. Ive got an appointment to get it tuned next weekend.
