Heads/Cam swap start-up issue help needed
11-30-2004, 01:31 PM
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Heads/Cam swap start-up issue help needed My installer just installed my Absolute Speed Stage II heads and a Comp 224/581-114 cam in my '04 GTO/M6, along with a set of Stainless Works LT headers. When we turned the key the first time the engine started great and after a minute or so settled into an idle of approx 800 rpm. After another couple minutes we ran the idle up to 1500-2000 with intent to hold it there for a couple minutes then bump to 3000-3500 for another minute or so.
After approx holding the throttle at 2000 rpm for a little over a minute, the left bank (only the driver's side) header started to glow...it was getting hot. We checked everything over (Plugs are light gray & dry, O2 connections good, fuel rail connections good, etc.) and tried it again...same thing again. We connected up AutoTap and everything showed connected and operating normal. We put it on the rack and noted that the left cat was also very hot so we thought it might be plugged...removing the cats and starting the engine had the header glowing again...not a plugged cat issue.
The heads were ordered as standard deck height and we installed new 7.40" pushrods. Checked for leaks around the intake, and even installed new intake manifold gaskets. Still a problem. It is only happening on the left side...
We're scratching our heads...any ideas on what to check from here?
After approx holding the throttle at 2000 rpm for a little over a minute, the left bank (only the driver's side) header started to glow...it was getting hot. We checked everything over (Plugs are light gray & dry, O2 connections good, fuel rail connections good, etc.) and tried it again...same thing again. We connected up AutoTap and everything showed connected and operating normal. We put it on the rack and noted that the left cat was also very hot so we thought it might be plugged...removing the cats and starting the engine had the header glowing again...not a plugged cat issue.
The heads were ordered as standard deck height and we installed new 7.40" pushrods. Checked for leaks around the intake, and even installed new intake manifold gaskets. Still a problem. It is only happening on the left side...
We're scratching our heads...any ideas on what to check from here?
11-30-2004, 04:04 PM
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Sounds like that bank is lean.
I have seen headers glow like that before. But that was on a carb setup and the cause of it was not enough initial timing. I dont see how one bank could be getting more or less ignition timing than the other so thats pretty much out of the question.
Sounds like a good place to start.
I would also check to see if there is a vacuum leak from the intake though that would have caused some Idle problems.
Only other thing I could think of would be the head on that bank has smaller combustion chambers and is making more compression.
All of these are shots in the dark man. Post up when you figure it out.
Brad
I have seen headers glow like that before. But that was on a carb setup and the cause of it was not enough initial timing. I dont see how one bank could be getting more or less ignition timing than the other so thats pretty much out of the question.
You didn’t mention checking for leaks in or around the headers. You might also swap oxygen sensors.
I would also check to see if there is a vacuum leak from the intake though that would have caused some Idle problems.
Only other thing I could think of would be the head on that bank has smaller combustion chambers and is making more compression.
All of these are shots in the dark man. Post up when you figure it out.
Brad
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11-30-2004, 04:44 PM
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The O2 sensors showed good on AutoTap, but that is a quick & easy swap that the installer said he was going to try today. The vacuum leak around the intake was one of the first checks, although they did it the "shade tree" method with cigarette smoke, it didn't show any "suction" into the mating surfaces.
And, uncoated headers will glow pretty easily when the heat gets cooking.
And, uncoated headers will glow pretty easily when the heat gets cooking.
11-30-2004, 04:49 PM
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Try the other shade tree method.
Use carb cleaner or brake parts cleaner. Spray it around the intake ports or anywhere else tou may suspect a vacuum leak. If the idle changes you have found your leak.
Brad
Use carb cleaner or brake parts cleaner. Spray it around the intake ports or anywhere else tou may suspect a vacuum leak. If the idle changes you have found your leak.
Brad
