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Headers with 2" primarys?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JanneB, Dec 17, 2006.

  1. JanneB

    JanneB Registered Member Premium Member

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    I have a 502 (http://paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=43943) and this week I got the AFR 315cc heads (http://www.airflowresearch.com/315bbc_rh.php).

    My Hedman headers I have now have only 1 3/4" primarys if I remember it right, a lot less than the 2" exhaust ports are on the AFR:s anyway.

    I have searched forever but it seems nobody makes headers for our trucks with 2" primarys, or do you know of some? There is a local guy who builds headers but he wants at least 1.000 euros for a pair, and I think it is too much. I know, I know, the heads were not cheap but what to do?

    One thing more to consider, I have lifted the crossmember for the adapter between the th400 and the np208 so maybe all headers ment for a truck would not fit?

    Suggestions?

    Janne
     
  2. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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  3. bayou blazer

    bayou blazer 1/2 ton status

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    Both of those headers are for 2WD trucks. I was in the same situation with my 502. Hooker does make 4WD headers with 1 7/8" primary tubes. I found an article from Chevy high performance and they had a 502 build that was nearly identical to my engine. They ran their engine with both "little" 1 3/4 primaries and bigger 2 1/8" primaries and it made around 25HP more with the bigger tubes. Even with the small tubes the engine still made 527HP with 608 FtLbs of torque. I am running my small tube headers for now until I can fab up a set of big tube ones. I think that you will have more than enough power even with the smaller tube headers.
    http://www.chevyhiperformance.com/techarticles/68318_502_ci_engine_build/index.html
     
  4. JanneB

    JanneB Registered Member Premium Member

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    Ok thanks, but I want the bigger primarys because the heads have those large ports and I do not want to loose power. I think I would loose more than in the chevyhiperformance link.

    I found one, Hedman #69130 but the driver side header look really wierd?

    What do you think?
     
  5. bayou blazer

    bayou blazer 1/2 ton status

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    I just looked at the Hedman and they appear to also be for 2WD trucks. You may get them to fit if you trim the collector. By the way the picture for the headers stated that it may not be the actual header. If you want the most power from that combo you may have to get some headers fabricated. It did not seem impossible to do though. You may give it a try.
     
  6. TeK

    TeK 1/2 ton status

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    Fabricated headers should give you the most power, as long as they are designed and built correctly.

    I'm debating on whether or not to buy a set of the 2WD headers to see if they will work. I've got the 1 7/8" ones now but want more flow.
     
  7. 1976Blazer76

    1976Blazer76 1/2 ton status

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    2wd headers won't work. I went through the same thing and bought some 2wd. They got here and I was mocking them up and they hit the transfer case crossmember because the collector tube is too long. 4wd headers have a shorter collecter tube.
     
  8. JanneB

    JanneB Registered Member Premium Member

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    Yea I propably go the fabricated header road. The 2WD headers with big primary tubes are not cheap, and if they have to be fabricated to fit then why not fabricate from scratch?
     

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