1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

exhaust manifold

Discussion in 'Chevy Trucks' started by gregh, Feb 25, 2002.

  1. gregh

    gregh Junior Member
    from indiana
    Messages: 8

    I have an 87 Chevy 4X4. When I bought it it needed an exhaust manifold on it because it was cracked. A year later the same thing happened, and then it happened again. What is going on? It is on the passenger side. I don't want to put another on until I know why. They cost too much. Help
     
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    does the truck have an AIR pump?it shouldnt,but can if its a HD model,is it hooked up,does it still have a catylitic convertor?.i assume the engine is a TBI 305/350.A couple of things to check,the timing,if its late a few degrees the exhaust wil run extremely hot,We melted a rubber exhaust hose on a Dodge that was 4 degrees ********.Late timeing lets to much heat out the exhaust,which raises the mainfild temp,and likelyhood of cracking.A plugged catylitc convertor makes it run hot too.Is is strange that you have cracked a few now,are you buying brand bew Gm manifolds,or junkyard take offs?.
     
  3. gregh

    gregh Junior Member
    from indiana
    Messages: 8

    exhaust

    it is a 350 engine, 3/4 ton. I do remember noticing the manifold getting red hot one time. I will check the timing. how do you check if the catalytic converter is bad? it does have one.
    It does have an air pump, which I thought about getting rid of and putting headers on but my friend told me that I need it to control the carb.
     
    Last edited: Feb 25, 2002
  4. MTCK

    MTCK Senior Member
    Messages: 346

    To check the converter, I take a sawzall, and make a clean cut a few inches in front of and behind it. Then remove it and take a look through it. Then throw it away and weld a test pipe in. Just kidding, don't do that, it would be illegal. One more thing to check with the cracked manifolds: there is a damper on the passenger side, that opens and closes, and it's been so long since I took all that stuff of my truck that I can't even really remember it's purpose, but if it were stuck closed, it could give you some heat buildup. I think heat is the culprit here though. Sorry I can't think of a better proceedure to check the cat.

    Marcus
     
  5. gregh

    gregh Junior Member
    from indiana
    Messages: 8

    exhaust

    anther question, will JB Weld work on this crack?
     
  6. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    He shouldnt have the dampner it was on the pass side manifold,it was used on carburated models only to put all the exhaust thru the intake crossover when it was cold,in order to warm up the intake quicker,the TBI doesnt have that.If your manifold got red,you have late timing,an AIR pump thats running once its hot,or a plugged cat.
     
  7. 75

    75 PlowSite.com Addict
    Messages: 1,382

    I'd be inclined to think JB Weld wouldn't be the best choice for the exhaust manifold, however I've never tried it either. If you decide to give it a shot make sure the manifold is clean before applying the stuff.

    In addition to what's been mentioned, are the engine and transmission mounts in good condition? If any of them are broken or getting weak the engine may move around more than it is supposed to, putting extra stress on the manifolds.
     
  8. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    "In addition to what's been mentioned, are the engine and transmission mounts in good condition? If any of them are broken or getting weak the engine may move around more than it is supposed to, putting extra stress on the manifolds."

    Exactly. Also, I have seen exhaust systems "rigged" with steel hanger straps, with NO rubber. Every exhaust mount should have a flexible portion, be it braided steel, or rubber. Without it, frame twist and any motor mount play like Rob mentioned will put a lot of undue stress on the manifolds.

    ~Chuck
     
  9. xybg5

    xybg5 Junior Member
    from Texas
    Messages: 3

    JB Weld

    JB weld doesn't work good on exhausts. They get to hot and the stuff flakes off like clay. Tried it on some leaks on my manifold.
     
  10. mike bisbano

    mike bisbano Junior Member
    Messages: 7

    Furnace Cement

    I too tried JB Weld on a hot area and it flaked off, really quick.
    However, I've had much luck with Furnace Cement.:D