Stg3 headers/ 1250 dominator

Discussion in 'Race 400/430/455' started by Buicks4Speed, May 10, 2002.

  1. Buicks4Speed

    Buicks4Speed Advanced Member

    I have 2 1/8 headers w/4" collectors and I'm going to be changing them into step headers, going 10-12" off the flang and steping them to 2 1/4. I also am planing to shorten them 2-3". Has any one ever done this to a wild 455 set-up with some dyno hp figures? Also I'm going on the general rule of thumb on the 10-12" and 2-3" shorter part which will get me real close or just a bit better than what I was, what is the actual math to go about figuring it any closer than I am.

    Next, I have a 1250 HP Holley with adjustable air bleeds and annular boosters part #80533. I've seen some carb shop carb with 3 curcuits and they opened up the intermediate curcuit air bleed alot leaving the main alone and stepping up the jet size. The carb was on a 455 with a at .050 270/280 cam, 12.5 comp. It was very crisp and responsive. Dual carb setup carbs seem to be the best out of the box cal. wise and run great in the middle of the power band but seem to be off up top, probably a little rich. what a good place to start with out doing alot of excessive trial and error. :puzzled:

    LOVING TO FLY WITH THE JUICE!!!:stmad: :stmad: :stmad:

    I put this post on "the bench" by accident. I ment to put it here.
     
  2. blownsmobile

    blownsmobile Member

    I have seen mixed results from stepped headers, It seems like they help the most on poor flowing heads which it seems you dont have to worry on that. or on heads wich dont allow a large enough tube to be used off the head and making a step header allows them to use the proper tube farther down the header. what kind of power and times are you running? sorry if you have covered those numbers before but I am new to this site.
     
  3. Buicks4Speed

    Buicks4Speed Advanced Member

    Times so far

    Ive' run a best of 5.65 at 122 mph in the 1/8th with a two stage nitrous. 180 hp out of the hole and another 150 as soon as I can hang on. 3300lbs 1.32 60ft 10.5 tire. I've heard from "motor " guys that they haven't seen a difference. But I've talked to alot of Nitrous guys that say its worth It :Do No: I've already got tubing on the way but I'm going to see what I can do with the shaft mount rockers first to see if they help out the top end hp. Plus I've got some clearance problems so I figured stepping couldn't hurt if I couldn't find anyone with some good direction on what to do.


    FLYIN'oN tHE JUICE!!! :stmad: :stmad: :stmad:
     
  4. blownsmobile

    blownsmobile Member

    thats a bad ass 60'!! I guess try it,but keep an eye on your 60' times, that will tell you the most. any guess on h.p.? my brain never seems to work right on 1/8th mile times. are you building a whole new set or cutting half of you existing ones off?

    In re reading you post about the fact most motor guys didnt notice any difference but the nitrous guys loved it is mainly because most guys run a header that is too big. when you hit the button and add 150+ hp now you are getting into the power range where the header will work. keep in mind as much nitrous you are using you must build the header to work with the nitrous on or off , not both. if you build it for the nitrous off it will be too small for when you hit the button and vice versa if built for the nitrous on. you are speaking of a 330 horsepower difference when you hit the button.
     
  5. blownsmobile

    blownsmobile Member

    Sorry, what total length are you shooting for? and what kind of rpm's are you turning?
     
  6. Buicks4Speed

    Buicks4Speed Advanced Member

    The tube lengths' are 34-39". I'm going to try and shorten them about 3-4". I'm trying to get it to run strong to 7000-7200. I think I'm going to need a size bigger cam though. Currently 268-270/274-278 at .050 .681 net lift.
     
  7. blownsmobile

    blownsmobile Member

    just getting rid of that 9" difference in length you have on those will definatly help. all tubes should be within 1" of each other. 34" should be the longest.:Brow:
     
  8. Buicks4Speed

    Buicks4Speed Advanced Member

    Sounds good

    I'll shoot for 34". I appreciate the input and I'll keep you posted on how it turns out.
     

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