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Thread: 99 obs tahoe 5.7 to 5.3 conversion opinion

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  1. #1
    Join Date
    Feb 2009
    Location
    Ada, Oklahoma
    Posts
    116

    99 obs tahoe 5.7 to 5.3 conversion opinion

    i want some opinions on what i should do, i have a 99 tahoe with the 5.7 with 180.xxx miles in it, had a bad knock that got worse so i parked it, in the process of pulling the motor and rebuilding it, well i found a 5.3 that my friend is not using, has wiring harness, pcm and everything, full motor, havent got the full details on the motor yet like the mileage or year it came out of. would i be better off rebuilding the 5.7 which im not sure how much will cost or putting the 5.3 in it which i can trade some stuff and basically get it for free and if so, what all would i have to change to put the 5.3 in and is it worth the trouble, thanks in advance

    will be missed.....05 Silverado extended cab sportside
    99 tahoe: 5.7 stock for now
    08 cbr600rr: full yosh exhaust, power commander, timing retarder, 520 conversion with sprocket -1 +2 and k&n filter

  2. #2
    Join Date
    Nov 2003
    Location
    Denton Texas
    Posts
    20,540
    if it were me and I had to keep the tahoe then the 5.3 would be going in. 5.7 will be pricey to rebuild and still have less power and fuel mileage after the rebuild.
    See my truck data in the "My Garage" section here... http://www.ls1truck.com/forums/my-ga...tml#post191709

  3. #3
    Join Date
    Sep 2007
    Location
    Broken Bow, OK
    Posts
    1,434
    I don't know about the mileage being better. My 99 2-door Tahoe I had with the 5.7 got better than our 2003 does now. Hard to say...
    Really depends on if you want a drop back in engine or something you may have a couple of headaches before you get it running.

  4. #4
    Join Date
    May 2010
    Location
    so cal.
    Posts
    96
    I know it wasn't one of the choices , but a 6.0 would be perfect in it !!
    SOLD:1992 ECSB Silverado lm7 5.3 Swap, TR220 cam, Circle D 3200stall, CBM street tune, Schoenfeld LT's, LS1 efans, transgo hd-2 60e, custom CAI, Autometer gauges

    Best 1/8 E.T. 8.86 @ 77.8 on 275/60/15 MT ET Streets with 1.92 60 ft.

    2000 RCSB 4x4 Lq9 swap...stock except mild 4l65e....for now

  5. #5
    Join Date
    May 2009
    Location
    hot & windy
    Posts
    1,117
    ^^ basically the same thing with bigger pistons.

    as for the swap - check out the LS conversion threads
    00 FRC - just top end, exhaust, and a hot-air intake
    99 Sierra - 5.3 / 5spd
    ↓ click the pic for the build ↓

  6. #6
    Join Date
    Feb 2009
    Location
    Ada, Oklahoma
    Posts
    116
    thanks for the input, looking at dropping the 5.3 in it or selling it as of right now

    will be missed.....05 Silverado extended cab sportside
    99 tahoe: 5.7 stock for now
    08 cbr600rr: full yosh exhaust, power commander, timing retarder, 520 conversion with sprocket -1 +2 and k&n filter

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