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glowing header

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mdevlin, Mar 22, 2004.

  1. mdevlin

    mdevlin Registered Member

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    how worried should I be if I run my blazer for maybe 10 minutes or so, and the header on the left hand side of the engine is starting to glow red? it doesn't seem to me like that should be happening, but I am even more confused why it is just the header on one side, and not both (or better yet, why at all)

    any ideas?
     
  2. Butch

    Butch 1/2 ton status

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    Do you have dual cats? sounds like the left side cat is stopped up. Either that or you have a restriction in the exhaust. Do not run the motor till you find it, you will cook the oil and waste the motor. /forums/images/graemlins/yikes.gif
     
  3. MJF

    MJF 1/2 ton status

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    I just went through this myself. Although I never totally fixed it, I did find out that you will cook your engine even with short test drives to see if you fixed it with the last repair.

    How about more info on your truck. Do you have headers like you said or stock exhaust manifolds? Are there air tubes going into the exhaust from the smog pump? Are there any tight bends in the exhaust that could cause a restriction? Have you recently done a tune up where you might have used a heavy duty truck application spark plug? The heavy duty plugs make the combustion chamber hotter as far as I can tell from my research. Is the truck backfiring at all when you let off the gas after a quick acceleration?

    Mine ended up being something bad with the air tubes from the smog pump. It was pumping tons of air into the exhaust & causing it to heat up & glow. Here's the other possibilities I came up with:

    Restriction in exhaust
    Exhaust leak(it would be backfiring when you let off the gas)
    Intake gasket bad(But it didn't help when I replaced mine)
    Carb running lean(Someone also said too rich would do the same)
    Vacuum leak in carb or intake gasket.
    Spark plugs too high heat range.I got mine down to only one side heating up & changed the plugs to the heavy duty ones as advised by the Kragen parts counter dude & then both sides were heating up again.

    After all the things I replaced: Carb, changed jetting three different times, intake gasket, dist, full tune up, removed air tubes & capped the holes, radiator flush, new oil pressure gage just to be sure, sealed the exhaust leaks, checked everywhere for vacuum leaks around the carb, & mine was still glowing.

    I think, most likely, I burned up something in the heads from all the test drives because there was nothing else I could think of that would make it glow like that.

    I hope this gives you a couple things you can try. If you have the time & money, I would check & fix any exhaust leaks, vacuum leaks, do a tune up, & take a look at your heads to see if the valves look burnt. I would do all of this at once rather than like I did & fix one thing & take a test drive & then fix another, etc...
     
  4. mdevlin

    mdevlin Registered Member

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    basically the story goes...i have been doing a rather lengthy rebuild/buildup on my 1984 K5 blazer. It was pretty much my first shot of anything this big (I mostly did very minor mechanic work myself before this project). I got the truck, used off a some guy in new hampshire that pulled a 350 out of a camaro I believe, and ripped out all the non-essentials (like A/C), along with gave it a 9" lift (6" suspension, 3" body). The engine seemed kinda tired, and started having oil pressure problems, so i decided that was a good enough reason to rebuild the engine (since I wanted to know how).

    Pretty much following the plans/instructions out of a couple of magazines and books, I tore down the engine, threw out everything but the block, brought it to a machine shop, had it cleaned, checked for cracks, then they bored it 60 over (apparantly it was already rebored once). then I got a 383 stroker kit, KB hypereutectic pistons, vortec heads, edelbrock performer vortec intake, and then an edelbrock 795cfm q-jet carb. I don't remember the details off the top of my head about the camshaft I got, but it was profiled more as a towing/low-rpm cam. I got it from crane cams. I also decided instead of going with a timing chain, to get a pete jackson gear drive system instead. I had a friend verify that I degreed the cam correctly, and that the timing was set at what we though was the right number. The distributor is a accel HEI setup...nothing too special.

    I figured it would be good to get some background on the engine. But as far as what you asked about the headers and spark plugs. not long before I decided to do the engine rebuild, I had a flowmaster exhaust put on by a custom exhaust shop that did a pretty lowsy job in my opinion. For example, when I left the shop, every once in a while the exhaust pipe would smack into the spinning driveshaft, but in any event, around the same time, the catalytic converters (the only thing I didnt get replaced during the exhaust install) somehow went bad, and clogged up and started glowing red. I brought it back to the shop and they replaced both converters.

    So...in theory I had a 2 year old exhaust system from the headers back. the truck definately has headers, but they are the original ones that came with the truck when I bought it. They have a nice coating of rust over them, and I have no idea what make they are.

    I did have plans to replace the whole exaust system from the engine back because I wanted new headers that i knew matched my new engine configuration, and also I hate the exhaust job the shop did, and I am not confident about how they replaced the catalytic converters. So if everyone thinks that the problem is most likely the exhaust, I could just escalate that. I still have a long laundry list of items to buy for the truck, so its been kind of a triage type thing trying to decide what takes precedence.

    Also, you mentioned in your situation the smog pump what partly the culprit. I didn't hook up any EGR stuff, so that shouldn't be an issue.

    I replaced all the gauges with autometer gauges, as far as oil pressure goes, I am pretty sure when I started it this weekend (I live in Massachusetts, so its still a bit cold) the oil presure was up around 60 I believe, and the engine (well, at least from what the temp guage is measuring) didn't even have time to warm up before the header started to glow. The truck does run rough, and it still seems to have some trouble idling on its own without me giving it some gas. I think it tries idling somewhere around 500rpms (which seems low to me).

    also, the spark plugs I am using are bosch platinum+4's and the wires are the normal bosch wire set.

    As far as your other ideas go, my first guess about why the engine was running a little rough was because the fuel mixture and maybe the idle speed needed to be adjusted some.

    I could also see there being some form of a manifold leak due to a bit of an accident I had while installing the manifold. Somehow, while using a torque wrench I snapped one of the grade 8 bolts I was using to bolt down the intake (it was the last bolt on the back right of the manifold). It was strange that it broke in the first place since i was using a torque wrench set to 35ft-lbs. (I tested the torque wrench to see if it was broken, and it was fine). But when the bolt broke, it cracked the very corner of the manifold. I used JB weld to stick it back together in hopes I wouldn't have to buy a new manifold, but I havn't seen any coolant leaks (there is a coolant passge right near the crack).
    So the other idea I was thinking of doing was testing the manifold for vacuum leaks or whatever. I have a vacuum gauge (and a compression one, although i am not sure a compression test would help at all for this) but I am not exactly sure how to correctly test the manifold vacuum.


    I know I rambled on quite a bit, but my gut is telling me tha the problem is the exhaust, because it seems like if it was anything else, both headers would be overheating, instead of just the left side, and if the manifold crack wasn't sufficiently repaired, I feel like either coolant would be leaking, or other things would be happening on the right side of the engine instead of the left.

    any opinions?
     
  5. MJF

    MJF 1/2 ton status

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    Ummm....I'm done. Time for someone who actually knows something about trucks to step in. /forums/images/graemlins/thinking.gif
     
  6. mdevlin

    mdevlin Registered Member

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    haha, join the club. I think I have been in over my head with this project from the start. I wont even get into my decision to rewire the whole truck. I think that is why i am quickly approach year 3 of this project.
     
  7. bigburban383

    bigburban383 1/2 ton status

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    Hey MJF:

    Spark plug heat ranges have absolutly no effect on combustion temperatures. Theres is absolutly no correlation between a "hot plug" and higher combustion temps. Well in the case of running a way to hot plug you'll melt the plug and then the combustion temps would drop significantly
    /forums/images/graemlins/histerical.gif
     
  8. jakeslim

    jakeslim 1/2 ton status

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    this sounds like your air/fuel mixture is off. I use to have "glowing" header syndrome until I changed to a new carb. problem solved.
     
  9. mdevlin

    mdevlin Registered Member

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    i could see the air/fuel mixture being off, I am working on getting the right info on how to tweak it on the edelbrock q-jets. It still confuses me though why this would result in just one side overheating instead of both.
     
  10. BAJA_BLAZER

    BAJA_BLAZER 1/2 ton status Author

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    It sounds to me like a very lean condition (too much oxygen) which will burn much hotter. If it is just on one side, depending on which manifold your running, I'd look for a vacuum leak on that side. If it’s getting that hot you’re also overheating the tops of the pistons and the exhaust valves. Not good!
     
  11. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I've a newer multiport fuel injected vehicle do this when one of the injectors stuck "wide-open", basically dumping a lot of fuel through the system. The excess fuel drowns out the cylinder and just gets pumped out the exhaust.....when it hits the hot converter it ignites and gets hot.
     
  12. mdevlin

    mdevlin Registered Member

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    hmmm, i will have to check for a manifold leak. it seems like that is the general concensus (which is what is possibly causing the wrong fuel mixture). I wont be able to until probably wednesday, but hopefully its not the end of the world
     
  13. bushmaster

    bushmaster 1/2 ton status

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    is the side with the cracked manifold the side thats glowing? it could be sucking air and leaning out mixture in that side or in 1 hedder tube
     
  14. mdevlin

    mdevlin Registered Member

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    thats the odd part. The side with the crack in the manifold doesn't seem to heat up at all, its the opposite side that starts glowing, but then again, as someone else pointed out to me yesterday, the manifold could have criss-crossed passages or something, and if the leak is where the crack is, and the passage near the crack happens to lead to the left side of the engine (where the overheating is happening) then that would explain it.

    also, this same person told me a real easy way to check for manifold leaks is to spray wd-40 along the runners while the engine is running, and if you can see/hear the wd-40 get sucked in (which usually also makes the engine sound a bit differant too) than that is where the leak is. The other test was that if the manifold leak is real bad, if I was to cover up the air filter, and the truck still ran, then there is definately a bad leak.

    I half feel compelled to assume it has to do with that crack in the manifold, and just get a new manifold and a new set of good gaskets. Partly because I feel like if that crack isnt the cause of the problem right now, it probably will be soon enough. I am not sure how well JB-weld holds up, and it would also be a good excuse to get the new line of polished intakes that edelbrock came out with this year, but after I get the pulleys and such back on my truck (a whole other problem) I am going to do that WD-40 test and hopefully the leak is obvious enough. Although I hate having to keep putting the engine through all this hell to find the problem. Between the overheating on the left side, and all the rough starts (which I am assuming are related) I feel like more bad is coming from all this testing than good. But with my luck the manifold isnt even the problem.

    so much fun....
     
  15. jakeslim

    jakeslim 1/2 ton status

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    just replace manifold. I also replaced mine when i changed carb. Ir really made the truck run 100% better and sputtering, dieseling and glowing headers went away. Manifold is a cheap fix. I went with a edelbrock performer bought at Pepboys.
     

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