La1 3400 sfi top half swap

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  • staytrue2u89
    • May 2026

    #1

    La1 3400 sfi top half swap

    Hey guys i have a 99 grand am with the 3400sfi engine..i was thinkn about putting a cam in and have heads built up a little with roller rockers the ls6 valvesprings stainless head gaskets etc...my question is how much extra power will lower stock internals take?? Do i have to put new main bearings, piston rings new connecting rods in??? Or can i leave stock bottom end????
  • caffeine
    • Jan 2012
    • 1489

    #2
    The bottom end can take quite a bit more power over stock
    '89 Firebird, 3500 Turbo, T56, 9-bolt/4.11
    '86 Fiero, 3500, 4-speed

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    • Hard Driver
      • Aug 2010
      • 77

      #3
      Originally posted by staytrue2u89 View Post
      Hey guys i have a 99 grand am with the 3400sfi engine..i was thinkn about putting a cam in and have heads built up a little with roller rockers the ls6 valvesprings stainless head gaskets etc...my question is how much extra power will lower stock internals take?? Do i have to put new main bearings, piston rings new connecting rods in??? Or can i leave stock bottom end????
      It's not horse power but rpm that will kill you engine.Keep it in a safe operating rpm range and you will be ok .

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      • caffeine
        • Jan 2012
        • 1489

        #4
        Generally I find the stock bottom end is OK to 7000 rpm.
        '89 Firebird, 3500 Turbo, T56, 9-bolt/4.11
        '86 Fiero, 3500, 4-speed

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        • Superdave
          Been there, Built that.
          • Sep 2004
          • 5850

          #5
          Somewhere in the 400 HP range is where they seem to start having issues. Keep the tune good and keep it below 7K RPM.
          Past Builds;
          1991 Z24, 3500/5 Spd. 275WHP/259WTQ 13.07@108 MPH
          1989 Camaro RS, ITB-3500/700R4. 263WHP/263WTQ 13.52@99.2 MPH
          Current Project;
          1972 Nova 12.73@105.7 MPH

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