Chevy 350 exh manifolds glowing red
12-12-2007, 03:48 PM
#17
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My bet is a vac. leak. Causes lean condition and high idle/ advanced timing from lost signal. Also make sure vac ports are routed correctly. Above throttle plate goes to advance, below goes to the auto trans.
12-12-2007, 04:42 PM
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Edelbrock carbs are known to drip from the venturis if things aren't right. This will make it idle wrong and run rich.
running rich makes the manifolds glow because fuel is still burning in them.
Several things are involved.
Exhaust restiction
Wrong fuel ratio
timing. More usually reduces the problem.
running rich makes the manifolds glow because fuel is still burning in them.
Several things are involved.
Exhaust restiction
Wrong fuel ratio
timing. More usually reduces the problem.
I have looked down the carb while it was running and did notice the fuel looked as if it was dripping into the carb at idle. I didnt know any different so looked no further.
12-12-2007, 04:43 PM
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^^^^ that was what I was thinkin too...I'd also look at the vacuum advance, my old Ford had that problem idleing down to cutting off and reversing rotation for a stroke. Ended up being that with which we altered the timing to make it run good, tuned the carb to run right, and after replacing the advance everything was off, tuned it back in to what it should've been, and all was well.
12-12-2007, 04:46 PM
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How can i cancel out the vac lines? Maybe pull one off the carb and cover with my finger? Or pinch the lines or something?
12-12-2007, 05:03 PM
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Make sure you don't have any vacuum leaks and then add timing and fuel until it starts to detonate under WOT, back it off a couple degrees and then tune from there. Sounds like your timing marks are off.
12-12-2007, 05:49 PM
#22
Dripping venturies.
Next check to see how much vacuum it has. Less than 12 at idle, you must find the problem.
More than 12 I bet the metering rods are to big!!! This leans down the idle circuit and it causes the dripping.
Find smaller rods or bigger jets for the primaries.
Also, how many turns out are the idle mixture screws? They need to be about 3 turns out to make the off idle circuit work correctly.
Next check to see how much vacuum it has. Less than 12 at idle, you must find the problem.
More than 12 I bet the metering rods are to big!!! This leans down the idle circuit and it causes the dripping.
Find smaller rods or bigger jets for the primaries.
Also, how many turns out are the idle mixture screws? They need to be about 3 turns out to make the off idle circuit work correctly.
12-12-2007, 08:20 PM
#23
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what I should have said was retard the timing, not advance.
On a 71 chevy I used to have, there was quite a range before the engine would idle any different.
burning lean will usually make the engine run hot overall.
clogged cats, I would think would get hot at the cats, not upstream.
On a 71 chevy I used to have, there was quite a range before the engine would idle any different.
burning lean will usually make the engine run hot overall.
clogged cats, I would think would get hot at the cats, not upstream.
12-13-2007, 12:58 AM
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check the pollution air pump (if installed). a bad one will cause glowing manifolds. the porting of the head alone wont do this. what is the stock timing? 8- 10*?. are you running headers? if so a slight glow is normal at idle(especially if they are cheep thin wall type)
12-13-2007, 01:30 AM
#25
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I had an old ride a few years ago, quite a few years ago as a matter of fact, that jumped time one late night on the was back to the base. Started running slower and slower and finally would not hardly go at all. Stopped about 0300 in the morning, knowing I was going ot be late for muster, and popped the hood. The manifold was glowing white. Never did run right again, guess the valves went out the exhaust pipe.
Without actualy seeing the engine perform, timing gets my vote. If they are glowing red at idle, I would definately find the problem quick or he will be back in it again soon.
Without actualy seeing the engine perform, timing gets my vote. If they are glowing red at idle, I would definately find the problem quick or he will be back in it again soon.
12-13-2007, 09:26 AM
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Dripping venturies.
Next check to see how much vacuum it has. Less than 12 at idle, you must find the problem.
More than 12 I bet the metering rods are to big!!! This leans down the idle circuit and it causes the dripping.
Find smaller rods or bigger jets for the primaries.
Also, how many turns out are the idle mixture screws? They need to be about 3 turns out to make the off idle circuit work correctly.
Next check to see how much vacuum it has. Less than 12 at idle, you must find the problem.
More than 12 I bet the metering rods are to big!!! This leans down the idle circuit and it causes the dripping.
Find smaller rods or bigger jets for the primaries.
Also, how many turns out are the idle mixture screws? They need to be about 3 turns out to make the off idle circuit work correctly.
The idle mixture screws need to be re-checked, I think they were 1.5 turns out last time i checked them?
12-13-2007, 05:00 PM
#28
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I had an old 84 Dodge with a slant-6 that did that a couple of times.
It was due to a faulty distributor cap (Carbon Tracking) not allowing a full spark to burn all the fuel in the cylinder, allowing the unburnt fuel/fumes to flow into the exhaust.
Changed the cap, my problem went away.........Your milage may vary.
It was due to a faulty distributor cap (Carbon Tracking) not allowing a full spark to burn all the fuel in the cylinder, allowing the unburnt fuel/fumes to flow into the exhaust.
Changed the cap, my problem went away.........Your milage may vary.
12-13-2007, 07:38 PM
#29
Try this, turn the screws out to 3 turns, start it and adjust the idle speed screw.
Vacuum is checked at the base of the card.
Edelbrocks have two ports on the front, drivers side is ported, so it only has vacuum at throttle, not at idle.
The passenger side should be full vacuum, full time.