305 to 350 what is needed
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From: Fritch, TX , 79036
305 to 350 what is needed
I want to switch my 305 out with a 350, my car is a 87 trans am 305 TPI. If I did this I would want to keep the TPI. Is it as easy as just swapping things out or are there anythings that need to be modified? And what about the ecm can it stay the same or do I need one for the 350? Thanks
Joined: Mar 2000
Posts: 43,187
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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
It will "work" without changing anything. But, you'd be best served getting an adjustable fuel pressure regulator to tune it to get more out of it. A more highly modified 350 might do better with 22 lb injectors, but I know I guy out here who runs BETTER with 19 lb in his highly modified ZZ3 TPI than he did with 24 lb.
Also, to get the most out of a 350, you should port the plenum and improve the exhaust. Those things are restrictions on a 305.
You should also watch out for the year of the heads on the 350 ('87-later or pre-'87) since the center two intake manifold bolts changed in 1987, and whether one- or two-piece rear main seal (you have one-piece, and the flex plate is different between the two).
The ECM itself doesn't have to change, although a custom programmed PROM would eventually help you optimize your setup. Some also say to get a 350 knock sensor & module to replace the 305 pieces.
------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. 0.030 over 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlock header mufflers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1/94.6 @ 5800' Bandimere.
Also, to get the most out of a 350, you should port the plenum and improve the exhaust. Those things are restrictions on a 305.
You should also watch out for the year of the heads on the 350 ('87-later or pre-'87) since the center two intake manifold bolts changed in 1987, and whether one- or two-piece rear main seal (you have one-piece, and the flex plate is different between the two).
The ECM itself doesn't have to change, although a custom programmed PROM would eventually help you optimize your setup. Some also say to get a 350 knock sensor & module to replace the 305 pieces.
------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. 0.030 over 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlock header mufflers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1/94.6 @ 5800' Bandimere.
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Joined: May 2001
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From: kemp,texas,henderson
I agree mostly w/ the above,I just did the same swap on mine and if you are keeping the injectors from your 305 which are the 19PSI, then yes get an AFPR and fuel gauge to mount on the fuel rail which I bought the accell and set it at about 48PSI w/car running then remove the fuel gauge. You will need to change flywheels but be careful to which you choose or you will be changing starters as I did and make sure on the heads cause the 87 also has the center style valve cover bolt pattern verses the around the top 5 bolt.You will also need to make sure the engine you choose has a computer friendly cam or you will have problems.Hope this helps
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