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Chevelle Headers on K5

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Roostr84, Dec 17, 2000.

  1. Roostr84

    Roostr84 1/2 ton status

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    I have heard that you can use chevelle headers on the blazer for better clearence. Does anyone know if there is truth to this?
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    What your looking for is clearence on the front drive shaft. A shorty header in my opinion would be best. I tried to use a set of headers sold under the name of Cyclone in the Jegs catalog and it interfered with the drive shaft. You also have to watch out that it doesn't hit the frame or the shackles. My concern here is the Chevelle runs a wider frame and the header may hit the frame. The other possibility is the Chevelle header will exit higher since the engine bay is more shallow then a truck so it very well may work out well. Most of the truck headers the bottom of the flange is a hair lower than the frame. This causes problems when comming past the transfer case. If I ever do put headers on I would look for the shorty styles that puts the flanges at a down ward angle in about the stock location.
    Now why do you even want headers? Most headers while yes them make more HP they tend to do it top end near redline. Even worse they move the torq curve up so that it comes on later. In a truck, especialy a 4x4 you want the torq to come on as low as possible. Most header have long primary tubes and quite honestly too large of diameter for the average application. They come in a one size fits all and often on a stock engine they do not help a great deal at a usable point. If that 25 HP gain is at 4,300 RPM you will rarely ever see the gain unless you run a high stall converter and that would be anti productive in a Truck. Where the truck likes to operate you may only see a 2 hp gain and an actull loss of torq where you need it.
    If you do get headers get a Tri Y or a Shorty style that will help keep the low end torq. Again don't over do it on the exhaust sytem. With true Duals 2.25 dia is more than enough. much bigger than that and you loose exhaust velocity. Exhaust Velocity creates a Scavanging effect (sort of a vacume) and actully helps pull the exhaust out of the cylinders when the valves open instead of having to force the exhaust out. A shorty or Tri Y will help that effect come on at a lower point so it will bring up the real usuable power at a better point for a truck than a long primary header will.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     
  3. Roostr84

    Roostr84 1/2 ton status

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    Well I was more curious about the clearence issue. I do have a lot of experience with headers and was looking for a tri-y design if not that a smaller 4-1. I was gonna use the 2.25 inch pipe with my 350 that is in there now. it is pretty helthy but I ave my original 307 manifolds that was why i was gonna step up. Thanks for the info though.
     

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