Hi Guys,
Last night swapped my Edelbrock 1405 for a Holley street Avenger 570 on my mild 302 just for fun.(Mind you the engine was running fine).
PCV connected to port on back of intake manifold(Cobra Type).Brake booster to port on back of the carb.
While car was idling less then 5 minutes notice the #4 header pipe start glowing red. Car was idling smoothly , winging the throttle slightly was done without any hesitation/stumble etc.
What would be the likely cause ?- engine is smooth, no undue noises etc.
Searching VMF-
How likely that the carb would cause this in one cylinder?
The Pcv port on the intake manifold leaning that cylinder?
The intake manifold suddenly leaking at that cylinder ?
Cam lobe/exhaust valve issue?
Timing issue ?
Note the motor seems to be running fine with the holley except for the red hot header tube..
Red hot at idle in less than 5 minutes sounds very odd.
I can't see how the carb would cause this, but having the PCV in front of one cyl would certainly tend to lean out the mixture going to that one.
Where did the PCV used to go?
Did you observe the engine idling under similar conditions before the carb swap?
Hi RICHA,
The PCV was routed the same previously. I did observe this under similar conditions as i have just put the engine back into the car after a cam and head swap. i.e when tuning the previous carb with a vacuum gauge.
Glowing headers is often timing related and/or a rich condition causing fuel to be burned late. Advance the timing a few degrees, just to see if it cures it.
Glowing headers is often timing related and/or a rich condition causing fuel to be burned late. Advance the timing a few degrees, just to see if it cures it.
Header glowing is NOT caused by a rich condition. A rich mixture burns faster than a lean mixture and provides a cooling effect as well. Late timing, lean mixture, exhaust leak at the manifold will all contribute to a hot header. Lean conditions can occur from vacuum sources tapped into that runner that are bleeding such as a PCV or a trans modulator/brake booster that is leaking.
Header glowing is NOT caused by a rich condition. A rich mixture burns faster than a lean mixture and provides a cooling effect as well. Late timing, lean mixture, exhaust leak at the manifold will all contribute to a hot header. Lean conditions can occur from vacuum sources tapped into that runner that are bleeding such as a PCV or a trans modulator/brake booster that is leaking.
Absolutely incorrect. Unburned fuel makes its way into the exhaust, and fired by late timing makes for absolute red headers. Go to a dirt car race, and you can pick out all the guys running rich.
__________________
1970 Mach 1 San Jose built Dec 23 1969. Marti says 1 of 7. Purchased in 1987. Original family owner of the powertrain 351C 2v FMX.
1993 GT 11,000 miles, Built 2-12-93 Auto, 3:27 Axle, cloth, sunroof. Untouched except for rubber and battery, Purchased new 8-3-93. still has the factory windshield fluid and new car smell.
Each can cause high temperatures in the exhaust but usually a single glowing primary would not be excessive fuel because the fuel unless the fuel was able to puddle in that primary.
I'd suspect the exhaust valve might be hanging open on cylinder 4 especially since you had the problem before the carb swap. But could be a number of other things aswell.
Replaced
Full floor pan
Firewall
Full cowl
Radiator support
Up next:
Shelby drop, 4 wheel drum to disc conversion, rebuild front suspension/steering, taillight panel, trunk floor,302 and AOD upgrade, wiring harnesses back in, and hopefully only patch panels on the quarters
E=MChuck Norris
Each can cause high temperatures in the exhaust but usually a single glowing primary would not be excessive fuel because the fuel unless the fuel was able to puddle in that primary.
I'd suspect the exhaust valve might be hanging open on cylinder 4 especially since you had the problem before the carb swap. But could be a number of other things aswell.
This I can agree with, and to add to that, it's unlikely that a corner would be more rich than the rest. That's why I suggested adding a few degrees of timing first, and go from there. That's the easiest adjustment to make, so try it first.
I'd suspect the exhaust valve might be hanging open on cylinder 4 especially since you had the problem before the carb swap. But could be a number of other things aswell.
I think i mislead you the only time i observed a glowing header was when i first fired up the engine to run in the cam- i adjusted the idle mixture screws on the edelbrock and it has never happened since- until i put on the Holley.
one other observation- while running and looking down the carb primary throats the Left hand side had fuel flowing while the Right hand side significantly less fuel flowing. Can one side of the idle circuit be blocked causing a lean condition on those cylinders fed by that side of the manifold ? ( and #4 being on the longest runner running the leanest?
Can one side of the idle circuit be blocked causing a lean condition on those cylinders fed by that side of the manifold ? ( and #4 being on the longest runner running the leanest?
Absolutely incorrect. Unburned fuel makes its way into the exhaust, and fired by late timing makes for absolute red headers. Go to a dirt car race, and you can pick out all the guys running rich.
That is true, but only when running WOT with a cam with a big overlap. They don't glow just loping around.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
#4 Header pipe glowing red
Finally here and loving it....
