Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

Going From TBI to Carb in my '91 RS.

Old 01-28-2012, 05:24 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Going From TBI to Carb in my '91 RS.

After my recent engine swap in my '91 RS, I made the decision to switch to a carb. I've got all of the components needed to make this swap (carb, intake, regulator, HEI distributor, etc...). I have two questions. The first is regarding the regulator. I have a four port regulator, and I know that I have to run a vent line because of the charcoal canister. If I'm reading the instructions that came with the regulator the vent port is in between the fuel ports and the adjusting screw, but I'm wanting to be sure of this. The style I have is listed at the following link: http://www.jegs.com/i/Aeromotive/027...oductId=750091 .

My second question is regarding the throttle cable. Since my car was originally a TBI the factory cable is close to working, but since I have a higher rise intake, and a 1" carb spacer the cable will only reach the carb is with the cable removed from the factory bracket. So, My question is would I be better off getting another cable, or making my factory cable work?

Any help on this would be appreciated.
Old 01-28-2012, 09:28 PM
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Re: Going From TBI to Carb in my '91 RS.

Don't confuse the vent line with the fuel return line. Two different things. If you have the typical Mallory 4309 regulator the feed line and the line to the carb both go around the circumference of the regulator, the fuel return line comes off the bottom. The feed line is 3/8", the return line is 5/16" from the factory. Fuel tank vent line is a seaprate line and goes to the charcoal canister.

Stock throttle cable will work fine- you just need a different throttle cable bracket. If you are using a Holley carb there are many to choose from that bolt to the carb bolts instead of the intake manifold (so differences in carb height won't affect the cable geometry).
Old 01-28-2012, 09:41 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

Okay, that's what I thought on the regulator. So, if I'm understanding it right there is no need to install a vent line from the regulator because basically the vent line is some what of a separate thing. Yeah I'm probably going to end up changing the bracket because I got it hooked up to the carb, but the stock bracket just is not cutting it.
Old 02-04-2012, 09:05 PM
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Re: Going From TBI to Carb in my '91 RS.

hey i got a 92 rs with the stock 305 im wanting to freshin it up a lil. I would like to put a cam, take my stock heads to someone and freshin those up too but should i keep the tbi or switch to carb what do yall think?
Old 02-05-2012, 03:23 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

If you're keeping the 305 I'd probably keep it fuel injected because you won't have to change anything in that area unless you want to. The reason I went to a carburetor was because it was going to cost me about the same either way to keep my 355 SBC fuel injected as it would to convert it to a carb, so I decided to go to a 4 barrel.
Old 02-05-2012, 08:44 PM
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Re: Going From TBI to Carb in my '91 RS.

If i keep my bottem end stock what is the most radical cam I can get away with. Im after low to medium end power and should i look into an aftermarket tbi like a holly or somthing? Or should I keep the tbi stock?
Old 02-06-2012, 05:42 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

In my opinion I'd contact COMP and get them to spec you out a cam, that way you get what need for your application. As far as the fuel injection goes you may want to update the fuel injectors to 350 injectors, but if you want to know all of the best stuff for the TBI engine upgrades check out the TBI section, it has everything you need to know about upgrading your TBI.
Old 02-06-2012, 07:04 PM
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Re: Going From TBI to Carb in my '91 RS.

I gotcha thanks for the pointers just got this car about a month ago itchin to turn a wrench on it. This week im gonna get rid of that stupid smog pump.
Old 02-06-2012, 07:24 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

The smog pump is a piece of cake to remove. You can have it done in less than an hour. The worst part is getting the right belt. Piece of advice on that, remove the pulley first (I think there is 3 bolts holding it on), and then remove the pump, it's a little easier that way.
Old 02-06-2012, 07:45 PM
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Re: Going From TBI to Carb in my '91 RS.

Ok how hard is it to plug the manifold holes? Im planning on geting headers later but for the mean time im gonna keep what i got
Old 02-06-2012, 07:55 PM
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Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

You should be able to find some plugs to put in them, I'm not sure what size they are because I took mine off after I had my headers installed, but they shouldn't be bad to do.
Old 02-19-2012, 01:10 PM
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Re: Going From TBI to Carb in my '91 RS.

i got a 1982 camaro that had a rebuilt 305 with a spun bearing but i swapped it for a 350 out of my 1990 k5 blazer, however we've hit yet another snag. My mechanic thought he could swap the intake manifold off the rebuilt 305 and thus 650 carb and 1" riser. He absolutely butchered my truck wiring (TBI wiring system included) and the middle bolts pattern changed on the intake manifold (angle less vertical more slanted) and im down to under $100. this is our last snag and it should've been checked in the first place in my opinion. My question is should i change the heads (forums say tbi heads blow anyway) if so which ones or should i get a new intake manifold for the 4 brl carb if so which one? Keep in mind im low on funds for now til it warms up out here.
Old 02-19-2012, 04:37 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

Yeah the center intake bolts changed between the '86 and '87 model years when Chevrolet went from the carbureted engines to the EFI engines. I've read where people have made the older intakes work by elongating the holes, but I purchased an intake that was designed fro the application.
Old 02-19-2012, 05:11 PM
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Re: Going From TBI to Carb in my '91 RS.

ill try to elongate them ill let you know if it works tomorrow.
Old 02-19-2012, 09:00 PM
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Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

Yeah that'll work, personally I've never done it, but I've seen people be able to do it and make it work.
Old 02-22-2012, 09:59 PM
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Re: Going From TBI to Carb in my '91 RS.

yeah i bought this bore tool for my drill worked perfect and i got everything but the front clip on. I just hooked up a Mr. Gasket in-line electric fuel pump and i cant get her to fire. my pumps rated 4 to 7 psi. I'd post pics but i use my Playstation 3. Do i still need a regulator or should my car be starting? Its a 1990 350 TBI converted to carb with a edelbrock 650 carb w/1" riser and GM stock intake manifold. What should my pressure be? Do i need a return line? I cant wait for my first drive in a 3rd gen camaro IM SO CLOSE.
Old 02-22-2012, 10:13 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

If you're using the stock style fuel pump then you'll need to use a return line, but I'm not 100% sure on if you're running an inline pump. Did you swap to an HEI distributor, or are you trying to run the stock distributor? Also, do you have the car timed properly? If it's not out of time that may prevent it from starting. Also, do you have power going to your distributor?
Old 02-22-2012, 10:49 PM
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Re: Going From TBI to Carb in my '91 RS.

i used the brand new HEI distributer(among other things) off the rebuilt 305 in the car (895 miles since rebuild with KNOCK) . we let it sit for a while and it fired i think it was flooded, and the timinig is quite a bit off. This is victory enough for the night though haha timing can wait for the morning. Do you think i need a regulator though or am i ok without one? I cant believe we're supposed to get a huge snow storm tomorrow haha its not even fair i wanna drive this bad little bow tie i cant wait!
Old 02-23-2012, 08:33 PM
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Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

To be honest I'm not sure on the regulator. Since you've installed a lower volume pump I'm assuming that you are not using the factory pump. In that case I'm going to say that you probably won't need a regulator.
Old 02-24-2012, 06:07 PM
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If the pump doesn't have a built-in regulator, you need a separate regulator, regardless of its volume capacity. Under low demand, an unregulated pump will overwhelm the carb's float needle/seat.
Old 02-24-2012, 07:35 PM
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Re: Going From TBI to Carb in my '91 RS.

why not just pull the pump out of the tank and run a mec. pump?
Old 02-26-2012, 12:18 PM
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Re: Going From TBI to Carb in my '91 RS.

90 350 doesnt have the cut out for a mechanical pump. motors in and running rscamaroguy thank you so much and 57kid you too i put a regulator in set at 5.5 lbs. but y mechanica broke my clutch cable and rigged up some ready rod deal bc he cant find the right part. long story short the car is sitting in my driveway and hes fired. so once again i need your help. i have a saginaw 4 speed but i cant find a mechanical clutch cable. i dont even know what i need to behonost
Old 02-26-2012, 12:20 PM
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Re: Going From TBI to Carb in my '91 RS.

the car wont shift while running with clutch to floor
Old 02-27-2012, 08:22 PM
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Re: Going From TBI to Carb in my '91 RS.

anyone? its so hard using this site on a ps3
Old 02-28-2012, 09:24 PM
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Car: 1991 RS Camaro w/ Factory T-Tops
Engine: Built 355 ci SBC w/ Carb
Transmission: Borg Warner T-5
Axle/Gears: 4.10 with Posi-Trac
Re: Going From TBI to Carb in my '91 RS.

Glad I could be of help to you. As far as the transmission issues, you may want to check out the drive line section on here to see about that.
Old 02-29-2012, 02:26 PM
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Originally Posted by SMAKA
mechanica broke my clutch cable and rigged up some ready rod deal bc he cant find the right part. long story short the car is sitting in my driveway and hes fired. so once again i need your help. i have a saginaw 4 speed but i cant find a mechanical clutch cable. i dont even know what i need to behonost
Originally Posted by SMAKA
anyone? its so hard using this site on a ps3
You need to start your own thread. The Transmission and Driveline forum suggestion is a good one.
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