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swaping out my lo3 305 to a 350 carb

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Old May 17, 2010 | 03:52 PM
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91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
swaping out my lo3 305 to a 350 carb

im about to swap in a 350 carb motor into my camaro. right now it has a 305 tbi in it. i was woundering what all im gonna need to do to swap this in. like will it bolt right up to my t-5 trans or will i need and adpater plate. this is my first swap so if you can give me any helpful tips that would be great. thanks
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Old May 17, 2010 | 04:06 PM
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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
What did the 350 come out of?

Are you planning on putting the TBI back on it, or downgrading to the carb?
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Old May 17, 2010 | 05:28 PM
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

it came out of a 1982 corvette and i plan on makin it carb
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Old May 17, 2010 | 05:35 PM
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Re: swaping out my lo3 305 to a 350 carb

downgrading??? its a tbi. i tried all avenues and my carb runs way better. but you have to be willing to tune it manually. if want it to be easy then keep the tbi. i still say that a properly tuned carb will flow and run better. but you have to manually tune it.
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Old May 17, 2010 | 06:10 PM
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five7kid's Avatar
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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
A carburetor isn't legal on a '91 model year in any of the 50 United States.

Of course, neither is an '82 engine.

You will need a different flywheel. EFI to carb is documented in the tech articles linked from the TGO homepage (also in the "welcome to the carb forum" sticky).
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Old May 17, 2010 | 06:19 PM
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Re: swaping out my lo3 305 to a 350 carb

also if he looks up my name i did a good write up. leagal???????????? come on. lol!!!!! if inspection is a priority and less tuning go tbi. if all out and inspection is not an issue go for carb.
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Old May 17, 2010 | 10:17 PM
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91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

yeah inspection aint a problem will the motor mounts that i have now work or will i need new ones
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Old May 18, 2010 | 12:29 AM
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

Ive done the swap myself and yes you can reuse the 305s motor mounts. The t-5 will bolt up as long as you use a 153 tooth flywheel. If the vette motor is a 2pcs rear main, you cant reuse the 305's flywheel. A new 153 tooth 2pcs rear main flywheel isnt cheap either. Youll have to either rework your stock engine wiring harness to work with the new engine, make your own, or only plug in the parts you need on the new motor and leave the rest unconnected. There is a great write up on how to modify the stock harness (which I used for my swap) in the LSx/LTx swap forum stickies entitled "How to prep a 3rg gen harness." Youll also either need to change your fuel pump to a mechanical one or carb friendly out of tank electric one with a carb pickup in the tank, or use the stock pump with a return style regulator. Good news is all of your gauges will work after you toss the computer, as long as you wire the water temp and oil pressure senders on the engine correctly.
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Old May 18, 2010 | 01:22 AM
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

for a pulg and play harness would i just need a harness that they used in the 1982 corvette or a different one
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Old May 18, 2010 | 01:26 AM
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

That I have no idea about. Im looking at this as just a standard 350 swap. Is the vette motor carbed or fuel injected?.
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Old May 18, 2010 | 01:29 AM
  #11  
91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

was cross fire injection also found 153 tooth 2pcs rear main flywheels for like 80 bucks dont know if thats cheap or expensive

Last edited by 91maroRS91; May 18, 2010 at 01:32 AM.
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Old May 18, 2010 | 01:32 AM
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

If your swapping to a carb, I think it would be easier to modify your stock 3rd gen harness.
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Old May 18, 2010 | 01:38 AM
  #13  
91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

oh ok im just tryin to figure out everything im gonna need to do for this swap my first one. i hope its gonna be a noticable gain in the hp and from the 175 my 305.also would i beable to use any of the accessories from my 305 like alternator, a/c compressure other stuff like that

Last edited by 91maroRS91; May 18, 2010 at 01:46 AM.
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Old May 18, 2010 | 01:44 AM
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

Depends on what the vette motor is rated at. If you go from a 305 to a 400+ hp 450+tq beast of a 350 like I did, then yea, you notice a difference
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Old May 18, 2010 | 01:55 AM
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

Originally Posted by 91maroRS91
was cross fire injection also found 153 tooth 2pcs rear main flywheels for like 80 bucks dont know if thats cheap or expensive
Are they new or used. I spent $300+ for my new billet steel one.
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Old May 18, 2010 | 01:57 AM
  #16  
travis401's Avatar
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

Originally Posted by 91maroRS91
oh ok im just tryin to figure out everything im gonna need to do for this swap my first one. i hope its gonna be a noticable gain in the hp and from the 175 my 305.also would i beable to use any of the accessories from my 305 like alternator, a/c compressure other stuff like that
The accessory brackets are pretty much universal for sbc. I reused the ones off my 305 on my 350. Just check both and see if the bolt holes are in the same locations.
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Old May 18, 2010 | 02:21 PM
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five7kid's Avatar
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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
Originally Posted by 91maroRS91
for a pulg and play harness would i just need a harness that they used in the 1982 corvette or a different one
Did you read the tech article I suggested? You've already got all the harness you need (with a couple of terminal changes, and adding a line for electric choke if you have that). Mostly you'll be removing (illegally, of course) what you won't be using.

Originally Posted by travis401
,,, also found 153 tooth 2pcs rear main flywheels for like 80 bucks dont know if thats cheap or expensive
Sounds reasonable http://www.summitracing.com/parts/ZZZ-50-6516/
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Old May 18, 2010 | 04:48 PM
  #18  
travis401's Avatar
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

I guess only the billet flywheels are expensive as ****.
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Old May 19, 2010 | 01:14 PM
  #19  
91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

now i just have to figure out which type of carb i should run
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Old May 19, 2010 | 01:22 PM
  #20  
travis401's Avatar
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

If its just a stock 350, a 600-650 cfm carb should be plenty.
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Old May 19, 2010 | 01:24 PM
  #21  
91maroRS91's Avatar
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From: Manchester Md
Car: 1991 Camaro RS, 1987 Firebird
Engine: 305 TBI, 350 TPI
Transmission: 5 Speed, Auto
Axle/Gears: N/A someoone tell me
Re: swaping out my lo3 305 to a 350 carb

im buying a whole new top end kit for it a buddy of mine told me to run a 800 cfm carb
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Old May 19, 2010 | 01:26 PM
  #22  
travis401's Avatar
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

ive got WAY more power than you and a 750 is enough for my motor.
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Old May 19, 2010 | 01:29 PM
  #23  
travis401's Avatar
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From: Arlington, Tx
Car: 91 Camaro RS
Engine: empty bay (for now)
Transmission: Built T-56
Axle/Gears: 3.42 stock posi disc
Re: swaping out my lo3 305 to a 350 carb

Depending on the top end kit, you may need a 700-750 cfm. But I dont see many street motors running 800cfm carbs. Except for the people that think throwing the biggest carb they can get on a motor is a good idea.
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Old May 19, 2010 | 03:25 PM
  #24  
five7kid's Avatar
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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
350 x 5500 / 3456 = 557 CFM. That's assuming 100% VE and single plane intake. A dual plane intake typically benefits from more CFM capacity, but a 650 CFM is about all you can expect a mild street 350 to need.
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Old May 21, 2010 | 07:28 PM
  #25  
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From: savannah, ga
Car: 91 chevy camaro
Engine: 383
Transmission: 700r4 built with corvette servo
Axle/Gears: posi 3:73
Re: swaping out my lo3 305 to a 350 carb

a crossfire vette motor is one of the most lowest rated hp motors ever put in the vette, a 600 cfm will do fine.....
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Old May 21, 2010 | 07:48 PM
  #26  
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Re: swaping out my lo3 305 to a 350 carb

The swap isnt all that hard to go from EFI to Carb. Me and my dad did it took us a long time but we wanted to make it look nice the hardest part was all the damn wires!!! Just do like my dad did a chair and some time and sort them all. Make it look pretty the first time so you dont one day get the urge to redo it all lol! good luck and I hope you have fun!
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