Glowing Exhaust Manifolds -- I give up!

[kpfoten]

Well, adjusted the fuel mixture with the gunson, and it wound up to be about 3.1%

My car seems to be running fine but the darn exhaust manifolds are STILL glowing! They glow from the engine down to an inch or so into the heat exchanger (from what I can see).

My engine temps seem to be fine (like 180). I don't have thermal reactors.

I have no idea what to do.

[Schrup]

Clogged cat?

[kpfoten]

No cat in a '77.

There's an EGR pipe from the exhaust to the EGR valve. The EGR valve is disconnected, but I compensated the lean condition I think. (The PO disconnected it.)

[Kevin Stewart]

if the oxygen sensor wire is broke or the sensor goes bad itll fill the cat with un burnt fuel, or basicaly plug it, this happened on my 82, Kevin

[slakjaw]

i would guess that there is still a fuel issue.

a disconnected EGR will raise exaust temps, as the only job the EGR valve has is to lower exaust temps in turn reduceing NOx.
(those damnd emmissions laws)

3.1% of what on your tool???

Kyle
71 911

[surflvr911sc]

3.1% CO

NO CAT!

This is weird, are you turning all the lights out at nighttime when this is happening? Do you have a Pyrometer? Then you could tell how hot it’s getting, maybe it’s not even an issue.

[350HP930]

Are you talking about them glowing while idleing or after the car has been driven down the road?

Headers can glow after normal operation if you view them in low light conditions.

[Superman]

If a cylinder is not firing then raw gas will get into the heat exchangers and burn there. So, an ignition miss will cause this. Or a very lean mixture.

Wait a minute. Just an inch or so into the sheet metal? On all cylinders? Well, if the mixture is rich enough like yours seems to be, then it must be normal. If you have CIS injectors, they are pretty easy to test. If some are clogged, then those cylinders would be leaner and...

Techron.

[Bones]

Techron, Techron,Techron, that's all you guys talk about and I can't get it over here! If anybody wants to go to the trouble and send a few bottles I have a Paypal account so I could arrange the funds easily.

[kpfoten]

Well, maybe it's normal. I've just never seen it on my other older vehicles before. Then again, it IS a 911 and is different then everything else...

I pulled the Injectors and checked the spray pattern, (didn't check volume, however), replaced the o-rings, etc. They looked good to me... Installed a new WUR, pressures were great.

The gunson said 3.1% (calibrated).

The '77 has no 02 sensor or Cat. EGR disconnect shouldn't be an issue if the fuel mixture is set properly, correct?

Finally, I'm assuming there's just a bunch of gunk caught up in the heat exchangers to give me small little flames. They get HOT though! The exhaust pressure seems strong although I wonder if a constriction (mouse nest or something) might be holding things up in the manifold...

Thanks

[kpfoten]

Oh yeah... I can see them glowing at night upon idle... (not even driving or revving the engine)..

[Doug Zielke]

Originally posted by kpfoten
Oh yeah... I can see them glowing at night upon idle...

You'd see the same thing near the exhaust ports of an idling m/c (air-cooled) engine.
Now....go out and play and stop worrying for nothing!

[kpfoten]

Okay! I'll let the little bit of grease burn out, make sure I've got some fire extinguishers and the insurance is up to snuff, and off I go... wish me luck...

[Steve@Rennsport]

Hi Kris:

Needless to say, this situation is NOT normal and requires resolution ASAP!

Glowing exhaust manifolds on N/A cars is generally caused by two things:

1) Excessively lean fuel mixtures

2) Late (retarded) ignition timing

EGR plays a role here by increasing EGT's but mentioned that you disconnected it. Air injection can also raise EGT's to point of making the manifolds glow, too.

If you observed a 3.1 CO% at idle with a shop quality 4-gas or 5-gas tester, I'd suggest that you make sure that your ignition timing is set at 33-35 deg total at 5000 RPM. You can watch the distributor work by observing the timing marks on the crank pulley with a good quality timing light.

Your distributor's advance weights might be stuck or the vacuum cannister might be defective.

Hope this helps, don't delay in fixing this.

[kpfoten]

Thanks Steve,

My air pump is still connected. Any recommendation to disconnect the air pump and plug the hose?

I will check my advance@ 5000rpm. The timing is set to the 5 degree mark at 1000rpms. Even if I don't rev the motor to above idle, I still get glowing manifolds.

[Steve@Rennsport]

Hi Kris:

If you are not required to pass local smog tests, I'd disconnect the air pump and block the passages in the heads with hex plugs.

Make sure that you are confirming ignition timing at 5000 RPM, the idle timing number is not important.

[kpfoten]

Okay, I took the belt off the airpump and ran it. Checked timing at 5000rpms and I'm not quite at the 35 degree notch. (maybe 5+ degrees off). I can't seem to advance it any closer?

The vacuum line is attatched to the dizzy. I hear of some people plugging this off? (I'm at 7200ft) If I apply vacuum (my mouth) to the tube to the dizzy I can see the parts (advance?) move.

Every once in awhile I'd get a miss at high rpms too.

Thanks for your advice

[kpfoten]

Forgot to mention that I run a pertronix ignition kit in the dizzy.

[kpfoten]

The glow seems to be most evident where the manifold meets the heat exchanger...

[kpfoten]

Update--

Disconnected the vacuum lines to the TB from the EGR valve, plugged with vacuum nipples. Disconnected air pump and plugged pipe. Set timing to 5 degrees. Ran the Gunson and the thing was running RICH. Adjusted to about 3% again.

I had done this awhile back and noticed the car seemed to run super rich too...

It appears as though the manifolds aren't glowing anymore except slightly where the manifold meets the heat exhanger (at night in the dark, but I can barely see it).

This is an absolute mystery to me... Hopefully I've fixed something well enough to drive it 2 hrs to the nearest Porsche mech...