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400 small block glowing ex. manifold?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by baldbandit, Jan 8, 2001.

  1. baldbandit

    baldbandit 1/2 ton status

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    I just purchased a 78 jimmy with a 400 small block . It wouldn't crank, so i pulled the spark plugs and cleaned them and it cranked. It smoked a lot at first and after a few minutes it wasn't smoking but a little. After approximately 15 minutes i noticed that the ex. manifold was glowing red . It was the drivers side 3/5 exaust port that was glowing and was red hot all the way down to past the 1st bend in the exhaust. I killed it, let it cool for 5 or 10 minutes and it cranked right back up. There was plenty of oil and it wasn't milky. So there isn't water in the oil. There was also plenty of water in the radiator. What would cause this problem? timming? overheating? I would think that if it was timming that it would be hard to crank or diesel when it was killed. I would also think that if it was overheating that both manifolds would get hot and it would be all of the ports instead of the middle one. Any help would be greatly appreciated. Thanks

    baldbandit
     
  2. blazer72

    blazer72 1/2 ton status

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    My 400's glow when ever it works hard or when its been run hard or for a long time. I bumped the timming up a bit and it helped some Headers glow and the 400 is the bigest sb there is and really does push thing to the edge. Mine has always done this first with the 700 holly carb then with the fuel injection it got worse. I started to run 17 degs time for base with a fast ramp up to 56 at 4500 rpm or with no load this helps alot. A 350 will do this to just not as easy as the 400 does.

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  3. baldbandit

    baldbandit 1/2 ton status

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    So this is normal? Do i need to install a lower temp thermostate? why was only one side glowing? Oh, and the truck has been sitting for about 3 years or so. Thanks

    baldbandit
     
  4. Chaz88K5

    Chaz88K5 1/2 ton status

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    sounds like timing to me...i had the same prob when i dumped a new motor in a few weeks ago...

    Chaz

    "Hondas look good under a k5's tires"
     
  5. CBLAZER81

    CBLAZER81 1/2 ton status

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    I'm wondering if it has cats on it(converters not the furry ones).Could they be plugged up and not letting the hot exhaust out?

    Chuck
    81 Blazer
    CO,USA
    <font color=red><A target="_blank" HREF=http://www.chucks81k5.coloradok5.com>http://www.chucks81k5.coloradok5.com</A></font color=red>[​IMG]
     
  6. mudfanatic

    mudfanatic 1/2 ton status

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    it could be that you have a plugged jet on your carb and a dual plane manifold, the top plane is getting enough fuel to keep two of the exhaust ports cool, and the other two are starving for fuel just enough that they run but can't keep cool. I knew someone who was messing with rejetting his carb and in the proscess leaned his carb out so far that he burned off the first 6" of ceramic coating on his headers after letting his rig run in the driveway for just 10 minutes or so.
    Dan

    <font color=red>get involved with land issues or lose the land</font color=red>
     
  7. K5 NUTT

    K5 NUTT 1/2 ton status

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    You have a lean problem. When my 76 Chalet was jetted at 70's for the colorado trip the headers glowed red at high idle after 10 minutes of run time till i changed the jets back to 73's. The other night i put her on the dyno at work and at 150HP...they were glowing again...gonna try some 75/76 jets and see how that goes. Just ran her on the dyno for a base reading to see how much more i get out of her when i TBI her next month. Also if she has been sitting for that long i would rebuild the carb!

    Azblazer

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  8. Blazer1970

    Blazer1970 1/2 ton status

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    I agree that it is most likely caused be a lean condition. If it is only on one side, a likely candidate it the intake manifold gasket where it seals to the head on that side. It is pretty common to develop an intake leak at that point. Check it with some propane or carb cleaner.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  9. baldbandit

    baldbandit 1/2 ton status

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    Thanks for the replys! It doesn't have cats under it. I'm really starting to lean toward timming because when I got home and cranked it, it back fired through the exhaust. When i get time i'll have to check timming. It is also fauling the plugs. It wouldn't run today unless i held it half throttle and even then it was running rough. I'll have to check for leaks around the intake and check timming when i have a day off again.



    Thanks
    baldbandit
     
  10. turbo

    turbo 1/2 ton status

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    Turbos ofter glow bright red when wun hard and exhaust can get real hot.
    The most common prob with too hot 400 is using non 400 heads without drilling the steam holes for the seamased block.
    IF regular small block heads without the speical 400 steam holes are used you get steam pockets and the cylinders don'd cool properly.
    Using a 400 head gasket as a template the steam holes can be drilled into other small block heads to solve the overheating.
     
  11. Russell Keys

    Russell Keys 1/2 ton status

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    Doublecheck your plug wires. Sounds possible there may be plug wires crossed. Just a thought-Russell .
     
  12. baldbandit

    baldbandit 1/2 ton status

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    Thanks! I'll check the wires also! I'm also going to get a rebuild kit for the "quadrajunk". It'll have to work for now , until i get the money for a new edelbrock!

    baldbandit
     
  13. K5 NUTT

    K5 NUTT 1/2 ton status

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    Now..now...lets not bash on the quadrajet! Best darn 4x4 carb around...just ask FWP about our trip to Crown King.....i didn't flood at all in all the off camber situations and the big change of altitude didn't hurt me abit. Allthough i will be swapping in TBI this month a q-jet is best for offroad...however a little planning has to be done if you decide to drive in a higher altitude in advance. When i went to Steve's "Why To K5 Run" i switched the main jets to 70's to run in 10K +...and i ran okay. The other guys with the holly's had nothing but fits and Stephen Watson's dad spent a good potion of the trail runs under someone's hood tweaking carbs to get another ten feet!!!

    Azblazer

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  14. bigjim321

    bigjim321 Registered Member

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    the last time i saw any thing like this come through my shop, it wound up being a cracked head and the extra air getting in and was adding to the heat problem.
    remember that if you have a 400 sm blk, it has thin walls between the to inner cylinders where the cooling jackets are. And if it has been to the shop for a bore or two then your looking at a good boat anchor.
    maybe do a leak test on the cylinders to see what its doing(cheapest items first)
    then if that show to be bad pull the heads off and have a shop check for cracks, i bet you find some thing out fast on this step.ands see if you can find out if its been bored or not?
    good luck

    Lack of mud makes a man mean!!
     
  15. blazer72

    blazer72 1/2 ton status

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    Both of my 400 are fuel injected ones an aftermarket TPI ones a Stock GM TBI. Both run hot at times glowing ex. manifolds, Both are bored 30 over one runs 11.5 to 1 the other is 10 to 1. Both have the steam holes though neather has 400 heads. One set is Edelbrock one set came in the 93 suburban.
    The TPI motor pushes about 530 hp and the tbi motor is about 370 hp. Neather has any problems. On the suburban the first 3 inches of the ex pipe glows when I have been towing the Blazer. The blazers JBA headers glow orange when it been worked hard. The why for in my case is that the ECMs keep the mix between 14.45/1 and 14.75/1 now all pipes do glow tha same on both sides on both trucks .

    I understand the jeep thing I drive a BLAZER!!

    Ken
     
  16. ken

    ken 1/2 ton status

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    The backfiring thru the carb incident leads me to believe it is a TIMING problem.

    ken
     
  17. ftn96

    ftn96 1/2 ton status

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    Sounds like a timing related issue. Not sure where though. You know when you watch those top fuel dragsters and all those big ass flames shooting out the pipes??? Well, most of this is due to keeping the exhuast open longer than it should be during the cumbustion stroke. Thus letting some, well, in your case, alot of the explosion to be released out in to the exhuast amnifold. Thus causing your pipes to be glowing red. So you might want to take the valve covers off and make sure you dont have any rocker arms broken, or valves sticking or anything else along those lines.

    Will work for parts, beer and sex.
    90 Jimi,350/700R4/241/10bolts/3.73's/33's/4"
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