Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

400 with headers-whats wrong?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BCB2, Aug 23, 2003.

  1. BCB2

    BCB2 Registered Member

    Joined:
    Jan 1, 2003
    Posts:
    11
    Likes Received:
    0
    Location:
    Wisconsin
    recently I decided to buy headers for my truck. The engine is a 400, probably with mild work done to it (I don't know specifics, I bought it as-is for $400 with edelbrock 750 and RPM intake, the guy tthought it had the matching cam, engine lopes just slightly at idle). Prior to the headers, I was running stock cast iron manifolds with dual exhaust, restricted at 1-3/4" or so for the first 3 feet or so, tappering out to 2-1/8" for another 6 feet and ending. (this is just a mud truck so nothing more was needed). The truck ran great, produced plenty of low end torque, and rarely overheated except with severe beating or a mud clogged radiator. So--- I put on the headers(open, no pipe). With the headers I lose all low end torque, and the motor barely idles. I ran it for mabye 10 minutes and the temp climbed right up to 230. Whats going on? I have heard that a more restrictive exhaust with more back pressure will give more low end torque, but what happened here was ridiculous.
    P.S.-I did check to make sure all plug wires were routed decent and not melting or grounding out on the headers.
    Thanks for any help /forums/images/graemlins/truck.gif
     
  2. Confedneck

    Confedneck 3/4 ton status

    Joined:
    Nov 1, 2002
    Posts:
    5,236
    Likes Received:
    0
    Location:
    Lehigh Acres, Florida
    did you use the right gaskets?, long tube or shorty headers? try running some exhaust off the headers i bet it will help you some...and as far as overheating..that sounds like a 400 thing to me lol
     
  3. BCB2

    BCB2 Registered Member

    Joined:
    Jan 1, 2003
    Posts:
    11
    Likes Received:
    0
    Location:
    Wisconsin
    I did not try running pipe off the headers. These are the longer headers ( I guess), just the cheap summit brand and I did check the gaskets as far as matching up(or at least being a bit larger than)with the ports. QUite a few of the guys I run with are just running open headers or with just the collectors and aern't having any trouble, this is with varying degrees of performance mods to the motor (some stock, some race gas) The thing about the overheating is that it did not happen before, only after the headers were installed.
     
  4. Confedneck

    Confedneck 3/4 ton status

    Joined:
    Nov 1, 2002
    Posts:
    5,236
    Likes Received:
    0
    Location:
    Lehigh Acres, Florida
    you sure it was running hot? or was the gauge reading hot? possible the sender went bad or got knocked around while you were putting headers on? btw, did yours go in from the top?
     
  5. SUBFAN

    SUBFAN 1/2 ton status

    Joined:
    Mar 23, 2003
    Posts:
    2,334
    Likes Received:
    0
    Location:
    Davenport, Ia
    Pull the spark plugs and see what color they are now. My guess is that your fuel mixture is off now that you have really opened up the exhaust. A lean motor will run hot.

    Headers generally put a lot more heat into an engine compartment. Remove the lip at the cowl to try and let some of that extra heat out. Run some pipe from the headers to somewhere, and get that exhaust away from the cab....
     
  6. loudnowlouder

    loudnowlouder 1/2 ton status

    Joined:
    Jan 29, 2001
    Posts:
    539
    Likes Received:
    0
    Location:
    Ellicott City, MD
    that shouldnt really happen, check your header gaskets, if you've got a leak it'll tend to run lean, which will make it real hot real quick, especially with cheaper headers, normally the cheaper the header, the thinner the tubing, which just dumps heat into the bay.
    the best way i know to keep headers from leaking is by using an ultra copper gasket, if applied generously that stuff holds like no other.
    definately sounds like you have a mixture problem, if your gasket is fine start tweaking the carb...
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    [ QUOTE ]
    I have heard that a more restrictive exhaust with more back pressure will give more low end torque,

    [/ QUOTE ]

    That's the biggest hunk of back country, redneck talking farmer bullshit I have ever heard. Anything you can do to reduce backpressure will increase horsepower throughout the RPM range.
     
  8. LittlePig

    LittlePig 1/2 ton status

    Joined:
    Aug 9, 2000
    Posts:
    299
    Likes Received:
    0
    Location:
    East Texas
    Sure, opening the exhaust/reducing pressure will increase HORSEPOWER, but running a slightly restrictive exhaust (usually via smaller-diameter pipe) will improve bottom-end TORQUE (Note the different terms used: HORSEPOWER vs. TORQUE) /forums/images/graemlins/deal.gif
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    [ QUOTE ]
    Sure, opening the exhaust/reducing pressure will increase HORSEPOWER, but running a slightly restrictive exhaust (usually via smaller-diameter pipe) will improve bottom-end TORQUE (Note the different terms used: HORSEPOWER vs. TORQUE) /forums/images/graemlins/deal.gif

    [/ QUOTE ]

    That is simply not true. Using slightly smaller headers will net more low end in some cases, but smaller, restrictive exhaust pipe will cut power throughout the RPM range.

    If it's a mud truck, low end torque is pretty useless anyway since you're usually on the loud pedal and on valve float all the way in and out of the woods.
     

Share This Page