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Headers and Exhaust for my 496

Discussion in 'The Garage' started by mountain4x4, Jun 1, 2005.

  1. mountain4x4

    mountain4x4 Registered Member

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    I will be running a blown 496 in my '74 k20. Its a little 177 cu in. Holley blower, with a ported 850 cfm Holley double pumper custom built by AED for my motor. It has an Isky 270/280 Megacam just like whats listed, but with a 112 degree LSA:

    http://www.iskycams.com/productdisp...c=101&dealer=no

    It should make 600 + hp/tq and rev to 5000 rpm maximum. It has a 700r4 tranny / np 208 t-case

    I currently have 1.75" primary Hooker Comp headers with a single 3" tailpipe, and was considering going with 2" primary Supercomps and a dual 3" exhaust. I want to build good low end torque without choking the motor (hence the small charger and relatively small cam for a blown 496). The first header listed is for a '68 + Chevelle/Camaro. I was hoping to avoid the low hanging, shackle interfering truck header problems. The second headers listed are for a truck, and also don't have equal legnth primaries...

    http://store.summitracing.com/defau...earchinresults=false&N=0&target=egnsearch.asp

    http://store.summitracing.com/defau...sults=false&N=0&target=egnsearch.asp&x=42&y=9

    Also, I will be building the exhaust myself, so I was thinking a 3" dual dumping in front of the rear wheels will be easy, a single with a 4" or so tailpipe will be more work, plus 4" exhaust pipe is expensive. I did a 2.5" dual on my Burb and only needed (2) 180* mandrel bends for the whole thing.

    Please offer any recommendations on the planned exhaust system. I am open to any changes in parts / design you may have, but please support your opinion with some reasoning. I am also interested to hear how the fit is on the Supercomp headers, and if you think the car/truck/other model headers will be the best fit. My current Hooker Comp truck headers fit GREAT, so I am thinking maybe the truck model Supercomps are the way to go...

    Or, do you think my current exhaust system is adequate, or will it be badly choking my motor?
     
    Last edited: Jun 2, 2005
  2. Burt4x4

    Burt4x4 3/4 ton status

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    Here is a look at the 73+ Thorleys I put in my 72's 454...
    [​IMG]
    Look at the different collector placements. i got the thorleys for function of the Tri-Y design said to help increase lowend torgue. They sure fit like crap but perform very well.
    [​IMG]
    Pass side comes close to the frame and I had to remove 1 of the x-member supports(I plan on putting it back with a ] in it to alow for the pipe to get by.
    [​IMG]
    Of coarse my frame is different...I thought I would shar anyway :D
     
  3. mountain4x4

    mountain4x4 Registered Member

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    Cool, thanks for the pics. Thorleys would be my first choice if my motor was going to make 450 hp or less. Their tri-y BBC Headers only have 2.5" collectors, I need 3" collectors for a dual 3" exhaust. I wish I would have got Thorleys for my '90 Burb, though...

    C'mon, theres got to be a bunch of people here with hot rodded BBCs in their trucks!
     
    Last edited: Jun 1, 2005
  4. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    If I were you, I'd change my tranny and T-Case.... I don't think a 208 is designed to handle 600+ hp, and I'm pretty sure with that much umph behind the pedal, you'll want a manual or something else built to handle the huge amount of torque and HP you are going to toss its way.

    MudJunkie can lend more info to this subject if he replies... he's got around 1000hp on his blown motor.
     
  5. mountain4x4

    mountain4x4 Registered Member

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    Yeah, the t-case might not last, I'll have to be careful with it in 4wd, but the 700r4 was specially built to handle high hp. I guess we will see. If the 700r4 doesn't last with all the upgrades done to it, I may need to get a built 4l80e. I got the 700r4 built when I had "only" 450 hp or so. I like OD trannies, so a sm465 is out. I don't know if a NV4500 is up to the task either. The NV5600 would be really cool if its possible to get it in there, but what about the poor clutch? Maybe an Atlas t-case or doubler is in its future as well...

    It's obviously not my DD, so if it breaks, it breaks... but I'm not an abusive driver.
     
  6. Burt4x4

    Burt4x4 3/4 ton status

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    Ya that is about were I am with my BBC. I don't know exactly what HP/Torque it is putting out but it is sure fun to drive :D Some day I will take my rig to a Dyno shop and find out :xmas:
     
  7. mountain4x4

    mountain4x4 Registered Member

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    Once you have a BBC is hard to go back to a SBC powered rig. I almost did, and would have got a Vortec 350 instead because of gas prices, but I already have lots of BBC parts, and it isnt my DD. Besides, a SBC will be hard pressed to leave those $40K turbo deisels in the dust on the highway. :D
     

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