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427 or 383 ?????

This is a discussion on 427 or 383 ????? within the Internal Engine forums, part of the LSx Technical Help Section category; alright I have a '02 T/A 6speed with a stock LS1, its got slp 1 3/4 headers and "3 borla ...

  1. #1
    Junior Member Pontiaco's Avatar
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    Navy blue
    2002 Pontiac Trans am

    427 or 383 ?????

    alright I have a '02 T/A 6speed with a stock LS1, its got slp 1 3/4 headers and "3 borla exhaust!

    This my list :
    102/102tb with fast fuel rails
    TEA cnc's 243s flowing 320 on the intake & 258 on the exhaust
    with 2.04 in & 1.575 exh
    millled .040=60cc's chambers
    400lb springs@ .650 lift

    I was gonna put this on my LS1, but now I wanna a LS3/L92 block so I can stroke it to 427 cubes!

    Will my heads & intake fit this block, I found a great deal on a short block,
    also will this block be a direct bolt on to my '02 T/A?

    I know Im gonna have to dish the pistons to have around 11.5 to 1 cr,
    or I'm I better stroking my LS1 to a 383

    This car is my weekend warrior and not my DD, but I like to keep my a/c and p/s and yes I got a 9in with 3.89 gears, thanks !!!!

  2. #2
    Sold: LS1 '85 El Camino ls1camino's Avatar
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    2000 Grand Prix GTP
    2000 Trans Am WS6 M6

    Are those parts you already have in your possession?

    There are little changes between the GenIII (LS1/2/6) and GenIV (LS3/4/7/9) motors, and none of those changes effect bolts holes for heads, transmissions, motor mounts, or front accessories (except in some cases of the iron blocks).

    I currently have cathedral port heads on my 427 LS3. At the time, they were one of the best flowing heads besides LS7 heads, but they require a bigger bore (4.125") than the LS3 has (4.060").

    Dishing pistons = lower compression. If anything, you want flat top pistons or domed pistons to increase the compression ratio. I have flat top pistons (with 3cc valve relieves) and I have a 11.8:1 compression ratio. This is pushing the limit of pump gas in a street car.

  3. #3
    Junior Member Pontiaco's Avatar
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    Navy blue
    2002 Pontiac Trans am

    yes I already have all of this parts !!!

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