wiring and computer change
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Junior Member
Joined: Jul 2001
Posts: 93
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From: DALZELL illinois
Car: 1991 firebird formula
Engine: 383
Transmission: th350
Axle/Gears: 3:73 posi
wiring and computer change
i have a 91 305 tbi and i wanna put a 350 in it if i changed to a carb or older block what stuff needs to be changed computer wise and wiring id like to keep the options. and if i put a tbi on it can i use the 305 tbi and would i have to change the chip. id like to know all the info you can tell me on this swap im hungry for torque and horsepower
thanx nick email me if u want at spanos4@hotmail.com
Joined: Mar 2000
Posts: 43,187
Likes: 43
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Humm, no one responded. Guess I'll take a shot (and at least move it back to the top where it will perhaps get some attention).
First, older 350 block: Depends upon how old. If '85-older, it will have a two-piece rear main seal, which means your flywheel/flexplate will not fit - no biggie, get a 153-tooth piece for an '82-'85 3rd gen. If '78-older, it will have the dipstick on the driver's side - using factory manifolds can make dipstick tube installation a challenge. Headers pretty much solve that problem, or a flex piece from Lokar (sp?).
I'd recommend some decent aftermarket heads like World Products S/R torquers to retain your accessory mounting holes and proper intake manifold bolt angle, while vastly improving performance. Very few "older" 350 heads do much performance-wise, unless you're willing to take a die grinder to them.
Now, carb or TBI: if emissions is a question, stay with TBI. Go over to the TBI board for advice on how to get the most out of it, including throttle body upgrade, intake upgrade, cam recommendations. The computer might need a chip change, but otherwise will continue to work properly.
If carb, you'll lose things like TCC lockup (if automatic), which can be regained with a lockup kit from Summit or Jegs; emissions could be a problem; gas mileage will likely drop. I wouldn't recommend going to a CC-carb - stick with TBI if you're thinking of that route. You can retain the wires needed for the ignition, gages, choke, etc.; cut out the rest.
------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ4 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (ported World 305 heads, Crane PowerMax cam, Hooker 2055 headers, 3" Catco cat & 3" catback w/Flowmaster, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).
First, older 350 block: Depends upon how old. If '85-older, it will have a two-piece rear main seal, which means your flywheel/flexplate will not fit - no biggie, get a 153-tooth piece for an '82-'85 3rd gen. If '78-older, it will have the dipstick on the driver's side - using factory manifolds can make dipstick tube installation a challenge. Headers pretty much solve that problem, or a flex piece from Lokar (sp?).
I'd recommend some decent aftermarket heads like World Products S/R torquers to retain your accessory mounting holes and proper intake manifold bolt angle, while vastly improving performance. Very few "older" 350 heads do much performance-wise, unless you're willing to take a die grinder to them.
Now, carb or TBI: if emissions is a question, stay with TBI. Go over to the TBI board for advice on how to get the most out of it, including throttle body upgrade, intake upgrade, cam recommendations. The computer might need a chip change, but otherwise will continue to work properly.
If carb, you'll lose things like TCC lockup (if automatic), which can be regained with a lockup kit from Summit or Jegs; emissions could be a problem; gas mileage will likely drop. I wouldn't recommend going to a CC-carb - stick with TBI if you're thinking of that route. You can retain the wires needed for the ignition, gages, choke, etc.; cut out the rest.
------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ4 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (ported World 305 heads, Crane PowerMax cam, Hooker 2055 headers, 3" Catco cat & 3" catback w/Flowmaster, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).
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