The Great Glowing Header Question

[03GC]

I know this has been covered to some extent before . It seems pretty common during cam break-in, but what about a couple hundred miles later?

I noticed it when it was idling for a couple minutes my dimmly lit garage. Can't see it in the daylight. I have seen this on 4-stroke motocross bikes idling also. Kinda scares you the first time you notice it!

The jeep has a cheap stainless dual outlet header on a 03 Grand Cherokee (upstream cats are gone, just running the rear cat).

I did the normal looking for vacuum leaks,loose TB, etc. Everything seems normal.

A wideband 02 is on the way to see what is going on(if anything)

Thanks
Paul

[jsawduste]

No worries, enjoy the the colors.

[03GC]

Did a little digging around today and it seems that stainless steel (and all steels from what I read) will start turning various shades of red starting at around 950 deg F. I have heard that exhaust temps run anywhere from 1250 to 1750 (just what I heard, not saying it is fact. If anyone knows for sure, please speak up).

Kind of makes sense that they glow, just looks crazy.

[SilverXJ]

On cam break in mine have always glowed. But never when at idle afterward. What cam are you running? Are you sure it is degreed in correctly? Is the cam sensor installed correctly?

[gradon]

Thinking it's unburned fuel in the exhaust due to incorrect timing, huh? I know mine was glowing when I first installed the 25.5# lt1s and destroyed my 3 month old magnaflow before the pcm learned.

[John]

EGT's (exhaust gas temps) of 700-750 degrees are normal for n/a around 900 degrees for turbos and lean conditions will raise them on up.

John

[SilverXJ]

Thinking it's unburned fuel in the exhaust due to incorrect timing, huh? I know mine was glowing when I first installed the 25.5# lt1s and destroyed my 3 month old magnaflow before the pcm learned.

Yeah. I've heard of the timing issue contributing to high exhaust temps.

My Cobra injectors run rich (~27# on 49 psi rail), but the PCM adjusted quickly and obtained its desired AFR easily... although I wouldn't doubt my cat is junk from all the cam break ins I have done on it.

How did you know your magnaflow was trash?

[IH 392]

Typically a lean condition ( the computer may need to learn the new engine?) or I personally have seen the results from the timing being retarded!, on the Chevy 4.3 V6's we were building at the machine shop for the Hyster forklifts, advancing the timing into reality and not something they pulled out of their buts! would cool the headers off by over 300* at idle and the glow would go away!
I'm not sold on the rich take?, if you give an engine to much fuel it cools off, and your power will fall off proportionately until the engine simply won't even run, to much fuel, not enough air.

[gradon]

The Jeep started pfffting and then choked itself out. When I took off the cat, the honeycomb was one solid melted mass(quick $70 loss). I'm all for high flow cats(have bought two magnaflows over the past 3 years--gave the first one to youngest bro so I could get one with two o2 bungs for the wideband), but until I get mine properly tuned, I'll make do with the ss track pipe w/ 2 o2 bungs I had custom made in addition to the mandrel bent 2.5" ss tailpipe. I haven't really spoke of it here or naxja(until someone recently asked for pics) due to bashings that are usually unleashed:

[gonridnu]

I believe you are talking about a glowing red header?

Iron based alloys such as 1040 and 4140 will not achive red heat until the approach the 1150 - 1250F mark, with mild steel 1018 perhaps in the 1050 range. Above these temps the material actually becomes non magnetic and the grain structure homgenous. Stainless and Inconel slightly higher, perhaps 1350, which is part of why they are so desireable as valves where the temps are much higher. These are not intermittent temps but actually related to measureable soak times based on the crossectional area of the part being heated. Header tubing is obviously thin and does not take much time to become heat soaked.

I would agree wtih the lean condition or retarded timing opinions. Glowing on WOT for an extended time is not uncommon but at idle I would be very concerned. Most engines cannot take exhaust temps in excess of 1250 - 1350 for extended periods before they suffer valve failure.

[03GC]

Turns out I had a vacuum leak after all,just not what you would think. The new TB has an adjustment under the throttle stop that was holding the butterfly open a hair. It was causing the IAC to freak out and cause a lean condition.

Now my idle is at a nice 800rpm with a little lope from the cam. It was 900-950 that was slightly erratic. I assumed it was from the computer trying to compensate for the cam.....NOT SO.

I figured this out after a talk with Zach at 505 (I bought most of my parts from him). Like I have said before, 505 has always been very helpful with parts and tech questions.

NO MORE GLOWING HEADER!!!!

Paul

[SilverXJ]

Well that was simple.

[gradon]

Zach's the man--he just sent Nick the offset ground crank a few days ago. What have you bought from 505?

[03GC]

I bought basically everything but the TB(Jeepers and creepers)
- KB944 kit rotating assy
-Cam .471/.484 lift ,211/217 dur at .050
-Springs,valves(LS1),keepers,locks,pushrods
-header
-injectors
-probably more I can't remember right now
I am pretty happy with everything, It started right up no problems. Zach was a big help with tech help(moral support). I build crankshaft machinery for a living and I have a hard time dealing in automobile tolerances (usually close enough is good enough). I live in a micron world at work (.001 inch =25 microns).

So ,I checked every part I installed in my engine. Run out on the crank,bearing clearances(with a bore gauge),camshaft run out, blah blah blah. It took forever ,but I never found anything I bought from 505 out of spec. Could have just put it together, and it would have been fine.Two things I did not use from 505 were the timing chain(went cloyes to get cam degreed closer) and I made my own teflon thrust button.

Do not even get me started on how much timing covers flex. They flex about .020 inch with VERY little end pressure from the cam.

Long story short, I think 505 is a good place to get parts and info from.

Paul