1990 GMC OBS 5.7 TBI swap to 5.7 vortec
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Junior Member
Joined: May 2023
Posts: 2
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From: Texas
Car: Gmc
Engine: 5.7 Vortec
Transmission: 700r4
1990 GMC OBS 5.7 TBI swap to 5.7 vortec
Hello , I have recently swapped my 5.7 tbi to a Vortec 5.7 . I知 trying to keep old wiring harness and computer but I知 not sure if harristuning is still pretty decent with his work . Is there any other recommendations that someone can lead me to .
Supreme Member
Joined: Feb 2021
Posts: 1,208
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From: WA
Car: 1989 IROC-Z
Engine: L98 350 TPI
Transmission: 700R4
Axle/Gears: BW 9 Bolt / 2.77 Posi
Re: 1990 GMC OBS 5.7 TBI swap to 5.7 vortec
You will likely get better answers at gmt400.com. Black bear is mentioned often there, don't know anything about them myself.
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Joined: Sep 2002
Posts: 253
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From: honolulu
Car: '86MCSS
Engine: 396 .030"
Transmission: M20
Re: 1990 GMC OBS 5.7 TBI swap to 5.7 vortec
You should do a search for tuning companies that have positive/negative reviews. Not sure of which year vortec 5.7 you're referring to. I've done a '92 OBS TBI 350 and swapped to vortec heads/intake retaining the TBI unit w adapter. I tossed a L98 roller cam in there as well. Main thing with the tuning was using an appropriate spark map that closely matched an LT1 which has similar head flow characteristics. Good luck!!!
Last edited by stew'86MCSS396; May 5, 2023 at 10:56 PM.
Joined: Mar 2014
Posts: 4,553
Likes: 806
From: South Ms
Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: 1990 GMC OBS 5.7 TBI swap to 5.7 vortec
Probably run decent by just bumping fuel pressure up to 16-18lbs. You may have to get a different fuel pump to support that though because TBI pumps only put out 11-15psi.
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