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SBC gt45 downpipe

Discussion in 'LS1, LS2, LS6, LT1, SBC Turbo and other GM Specfic Turbo Tech' started by Andy736, Mar 29, 2017.

  1. Andy736

    Joined:
    Oct 16, 2015
    I have a 355 running low boost 10-12psi max. eBay gt45 turbo. Will a 3" downpipe be ok or should I go 3.5?
    3.5 is gonna be really, really tight. Only looking for around 600-650 crank HP. Thanks.
     
    Andy736, Mar 29, 2017
    #1

  2. M&M Turbochargers

    Joined:
    Jan 31, 2011
    i i remember corectly you should have you down pipe 1.25x the turbine exducer 77mm to inch 3.03 ,,, 3.03 x 1.25= 3.79"

    but ask around

    we run 3.5 on our gt45 shop truck project
     
    M&M Turbochargers, Mar 29, 2017
    #2

  3. Mnlx

    Joined:
    Sep 20, 2009
    Like m&m posted, the 1.25 rule is what most use. Go 3.5" if at all possible as the Id of the 3" is .150-.200" smaller than the turbine exducer.
     
    Mnlx, Mar 29, 2017
    #3

  4. flyinhillbilly

    Joined:
    May 8, 2006
    3.5 on mine and it works great. No idea if the 3" would work, but IMO you're getting around the upper end of what a gt45 will do at that power so I'd err on the side of caution.
     
    flyinhillbilly, Mar 29, 2017
    #4
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