OOOOps. Cherry red exhaust manifold!! 1983 V6 - El Camino Central Forum : Chevrolet El Camino Forums
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Old 02-14-2008, 09:24 PM
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Default OOOOps. Cherry red exhaust manifold!! 1983 V6

Yesterday after a day of running very smoothly in fact so much so that I commented on it to the wife, suddenly it started running rough. Like a missing cylinder but more irregular and not much pull. Tried adjusting the timing a little more retarded as it seemed to be pinging when pushed. The oil pressure was normal, the engine temp was normal, all gauges were normal, just a rumbly missing feeling and no power on acceleration.

Limped home with the promise to fix it today. When I ran it this afternoon it was still "missing" intermittently and rambling. I checked all the spark wires and all were fine. Checked the distributor and all looked fine. I decided it must be a sticking valve so I went and got some Rislone for the crank case to see if that would loosen it up. Got home after dark so put the quart of Rislone into the crank case and then reved it to about 2000rpm long enough to get the engine temperature up to normal level. Then I shut it down and there was a big report (explosion) from the exhaust.

This would indicate a lean mixture. Then I walked around and looked under the hood...remember its after dark now....and to my surprise I saw that the left exhaust manifold was CHERRY RED. The right manifold was dark.... normal.

These symptoms reminded me of the time the catalytic converter on my Escort got plugged, but the EC doesnt have a catalytic converter and there is only ONE exhaust so I would have expected BOTH manifolds to glow cherry red. Or maybe not???

Or this would indicate a lean mixture in the left bank, right?

Any idea what the problem is and where to start to fix it?
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  #2  
Old 02-14-2008, 09:44 PM
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You don't by chance have a leftover heat riser valve in your exhaust do you? I had one on my 79 Z28 and on my current 74 Elky. If that valve flapper gets stuck closed it can block off the exhaust on one side. It's usually on the passenger or left side of the engine looking at it from the front bumper.

Just a thought...

BTW, I got rid of it on both cars...

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Old 02-14-2008, 09:53 PM
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I will have to look in the morning and see. But in this case, its the driver side that is cherry red. Maybe there is one on the left side on my engine?
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Old 02-15-2008, 09:21 AM
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Sounds like one side of the main jets might be clogged and half the engine running lean. Slowing the timing down will only make that worse.............Dan
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Old 02-15-2008, 04:18 PM
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Wellll, slowing the timing down DID make it worse.

AND, I checked the heat riser, and its on the starboard side, not the side that got hot. Also it is vacuum operated and not connected.

NOW, the question is, does the vacuum cause it to open or cause it to close???
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Old 02-15-2008, 05:45 PM
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Well, I know from how mine was set up that there was an aluminum adapter screwed onto the exhaust manifold with a short round protrusion in the middle of it. To that protrusion was connected a flexible tube that went up to the snorkel of the factory air cleaner right underneath the "thermac" valve. It was designed to channel warm air to the carb to aid in cold starts so it's conceivable that to make the system work the vacuum signal would be activated when the engine was cold. That is probably where the TVS or thermal vacuum switch came in. THe TVS was screwed into the top of the water inlet on the manifold and had 5 vacuum nipples on it. Since it was in direct contact with the coolant flow and located directly above the thermostat it was defintely involved in emissions control and cold starts.
I know one set of nipples went to the Thermac and I believe the other set was originally routed to the vacuum can that pulled on the rod that actuates the exhaust mounted heat riser flapper. The remaining connector was for full manifold vacuum.

Other possibilities are crack in the exhaust valve, Carb issues, etc.

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Old 02-15-2008, 08:23 PM
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Default red pipe

I would bet that the missfire is the whole issue here. Cure that and you cure all the symptoms. With a cylinder not firing, you are dumping unburned fuel into a hot exhaust manifold. This could explain the glowing manifold and the explosion. A cylinder balance test should locate the dead cylinder. Then go from there, ignition, compression etc.
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Old 02-15-2008, 08:28 PM
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Well, that makes it easy, only three cylinders to check...#

I am sure the vacuum operated valve is open when no vacuum applied since that side of the manifold was normal.

So now I need to find out which cylinder is not firing. But I am off to San Diego CA for three weeks so it will have to wait until I get back.

Thanks for the various inputs. I think the dead cylinder direction is right about the hot exhaust manifold.
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Old 03-13-2008, 10:05 PM
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Well, after returning from CA I, today, checked the missing cyl theory and found all three cyl on that bank are firing correctly, just intermittently and rough. So now I am going to check out the "lean on one side" theory. Going to remove and clean the carb tomorrow and see if the main jets are ok.
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Old 03-14-2008, 12:40 PM
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Default Crappy gas these days!!!

IT IS FIXED ! ! !

I didn't have to remove the carb.

I bought a $1.98 can of Carb Cleaner, sprayed the outside of the carb thoroughly, then sprayed the inside of the carb. Then started the engine and sprayed the cleaner liberally into the throat until it stalled the engine. Then I removed the fuel filter and sprayed cleaner into the line both ways and replaced the filter...it was new a month ago... Then I let it set for 15 minutes and restarted the engine. Then while revving the engine I poured ATF into the carb until it stalled the engine. I let that sit for 30 minutes and then went out to take a drive...blowing clouds of smoke from the ATF out the exhaust for about a block. Then continued the drive onto the highway at 60 mph and found it was cured. Running like a top now.

Apparently I was the victim of our crappy gas that separates out gum deposits whenever a car is left to sit for more than a week. In the future I will let the gas sit in the tank for 3 weeks before using it and the filter will then catch the crap!!

I use AV Gas in my lawn mower for just this reason, but its too expensive to use in the El Camino. Stabil is just as expensive when you add it to the cost of the gas and it doesn't work that well anyway. At least in my lawn mower I can now let it sit over the winter without having to remove and clean the carb every spring. Wish there was a similar solution for the El Camino.
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