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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.

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Old 09-12-2011, 08:04 PM   #1
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88 Chevy 305 TBI conversion to Carb.

Hey folks, im new here to the forum, i understand this is a Camaro/Firebird/Etc. Forum but i've read a few posts and u guys seem to know what ur talking about...

Anyhow, I need some help fellas, I have a '88 Gmc Sierra 1500 SLE w/ stock GM Chevy 305, and for the past 2 days I've been debating on switching it from TBI to Carburated. Only problem is I barely know where to start...

I have viewed several posts on here about TBI to Carb. Conversions but would really like to have some info guided directly to me instead of having to look around all day long, lol...

So my basic question is:
  • What is the CHEAPEST yet EFFICIENT way to convert from TBI to Carburated????
Not gonna lie, I am on a tight budget considering I just started a new job 2 weeks ago after bein laid off for a year an i just want the best yet cheapest way to convert this without spending TOO much time on it..

and thats it folks, lookin forward to hearing from u all and im happy to be here.

THANKS!!!

Chris
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Old 09-12-2011, 08:46 PM   #2
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Re: 88 Chevy 305 TBI conversion to Carb.

Tight budget doesn't cut it - it's a $1000 job unless you are good at trading parts and getting deals on used stuff.

You need:

Carb $250+
intake $250
distributor $125+
TV cable geometry corrector $20
throttle brackets $30+
RETURN-STYLE fuel pressure regulator $100
Method to lock TC $100+

That's $1000+ with the misc junk that it'll take (like hose barbs, rubber fuel line, fuel pressure guage, etc. So ... besides the fact that it's not legal, it's not for a light wallet. And to top it all off, it'll take you at least a week to work out the bugs, even if you don't work a 40hr week. And in the end, you'll gain nothing, but you will lose serious mpg and cruise control functions.

I'd seriously reconsider.
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Old 09-12-2011, 09:24 PM   #3
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Re: 88 Chevy 305 TBI conversion to Carb.

Quote:
Originally Posted by camaronewbie View Post
Tight budget doesn't cut it - it's a $1000 job unless you are good at trading parts and getting deals on used stuff.

You need:

Carb $250+
intake $250
distributor $125+
TV cable geometry corrector $20
throttle brackets $30+
RETURN-STYLE fuel pressure regulator $100
Method to lock TC $100+

That's $1000+ with the misc junk that it'll take (like hose barbs, rubber fuel line, fuel pressure guage, etc. So ... besides the fact that it's not legal, it's not for a light wallet. And to top it all off, it'll take you at least a week to work out the bugs, even if you don't work a 40hr week. And in the end, you'll gain nothing, but you will lose serious mpg and cruise control functions.

I'd seriously reconsider.
I mean, i kinda figured that, im workin w/$700 alone for the engine so far, and meant i dont wanna spend like a month without a ride, i can deal with a week or two worth of work with it...

and i have come across some deals so far but havent acted upon them, though i should..

an i know this may sound dumb to some (or all) but reason behind wanted it switched to Carb is I wanna put this on:
http://www-b.jcwhitney.com/hood-scoo...wx?filterid=j1

a Finned Street Scoop, if i could make it fit my TBI i would just buy it an be done with it, but im doin whatever it takes so far. I've already got $800 in my interior and another $1000 on the exterior and so the engine an trans is next..
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Old 09-13-2011, 02:37 PM   #4
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I'd say just buy the scoop and put it on the TBI.
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Old 09-13-2011, 03:04 PM   #5
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Re: 88 Chevy 305 TBI conversion to Carb.

Would it work through?? I've measured my Throttle body with a tape measurer and its 5 1/8 on inner diameter and bout 5 1/4 on the outer diameter, just not sure if it would work with a throttle body though...

Chris
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Old 09-13-2011, 05:36 PM   #6
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TBI and the typical aftermarket carb have the same air cleaner mount size.
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Old 09-13-2011, 06:35 PM   #7
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Re: 88 Chevy 305 TBI conversion to Carb.

Hell yeah, thanks man, u just saved me a couple hundred bucks, thats really wut i was wonderin the entire time, if the scoop would fit a TBI but everyone i talked to said no an told me I would have to switch the TBI to Carb...an yet i fell for it, lol

So my final question: What else will I need to mount/install the scoop on my TBI???

Im assuming just an extended throttle cable, but may be more than just that???

Chris
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Old 09-16-2011, 11:16 PM   #8
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Re: 88 Chevy 305 TBI conversion to Carb.

I just got through with the TBI to carb swap on my '90 Suburban last year. I've been extremely pleased, and it only cost about $300 total. I sourced the distributor used off of ebay and the carb as well. $30 carburetor rebuild, and the rest of the cash went into an intake, fuel pressure regulator, and the necessary fittings.

Putting old myths and arguments aside, a carburetor and fuel injection do exactly the same thing, and they give very similar results. IF you know what you are doing with a carburetor (a quadrajet), you can receive the same or better results as a factory TBI setup. That being said, tuning a carburetor properly is an artform, and takes a lot of time and patience. That, and you'll never get the ability of fuel injection and a computer to adapt to its surroundings (pressure, temperature, etc.)

That being said, I chose simplicity (carburetor) over complication. It's not right for everybody, but if you know what you're doing, you can make it worthwhile. The deciding factor for me was the 3rd TBI ignition module in a row that fried. I got tired of getting stranded on the side of the road, put a carb on, and I've been good ever since.

If you're only interested in a carb to mount a scoop on the hood, I'm afraid I can't help you. If you ever start having problems with the TBI, and get tired of constantly replacing over the shelf parts because they aren't any good, I can help you out with a parts list and step-by-step process to make the conversion.

-cal30sniper
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Old 09-20-2011, 07:56 PM   #9
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Re: 88 Chevy 305 TBI conversion to Carb.

Quote:
Originally Posted by cal30_sniper View Post
I just got through with the TBI to carb swap on my '90 Suburban last year. I've been extremely pleased, and it only cost about $300 total. I sourced the distributor used off of ebay and the carb as well. $30 carburetor rebuild, and the rest of the cash went into an intake, fuel pressure regulator, and the necessary fittings.

Putting old myths and arguments aside, a carburetor and fuel injection do exactly the same thing, and they give very similar results. IF you know what you are doing with a carburetor (a quadrajet), you can receive the same or better results as a factory TBI setup. That being said, tuning a carburetor properly is an artform, and takes a lot of time and patience. That, and you'll never get the ability of fuel injection and a computer to adapt to its surroundings (pressure, temperature, etc.)

That being said, I chose simplicity (carburetor) over complication. It's not right for everybody, but if you know what you're doing, you can make it worthwhile. The deciding factor for me was the 3rd TBI ignition module in a row that fried. I got tired of getting stranded on the side of the road, put a carb on, and I've been good ever since.

If you're only interested in a carb to mount a scoop on the hood, I'm afraid I can't help you. If you ever start having problems with the TBI, and get tired of constantly replacing over the shelf parts because they aren't any good, I can help you out with a parts list and step-by-step process to make the conversion.

-cal30sniper
Hey bud, thanks for the info, i havent really dont much else to it yet....ever since this post went cold i kinda figured i was at a deadend, lol, but i've been lookin at carbs an all still an have found everything i need around $200-$300 price range...
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Old 09-20-2011, 09:30 PM   #10
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Re: 88 Chevy 305 TBI conversion to Carb.

Good deal man. Sorry, it just rubs me wrong when people get gunned down on here for wanting to go carbed. I've seen that "it costs $1000+ to convert" argument used way too much. Yes, it might cost $1000 to buy everything brand spanking new, but by the same logic, it would cost nearly $3000 to buy a completely new fuel injection setup and make the swap. I've never heard of anyone actually spending that much on either, used parts are just so plentiful that truth be told, it doesn't cost that much to go either way. These vehicles are much more alike in their similarities than their differences, especially the TBI and carb cars.

Good luck with the swap. You won't regret the results if you do it right.

-cal30sniper
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Old 10-01-2011, 07:51 PM   #11
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Re: 88 Chevy 305 TBI conversion to Carb.

Quote:
Originally Posted by cal30_sniper View Post
I just got through with the TBI to carb swap on my '90 Suburban last year. I've been extremely pleased, and it only cost about $300 total. I sourced the distributor used off of ebay and the carb as well. $30 carburetor rebuild, and the rest of the cash went into an intake, fuel pressure regulator, and the necessary fittings.

Putting old myths and arguments aside, a carburetor and fuel injection do exactly the same thing, and they give very similar results. IF you know what you are doing with a carburetor (a quadrajet), you can receive the same or better results as a factory TBI setup. That being said, tuning a carburetor properly is an artform, and takes a lot of time and patience. That, and you'll never get the ability of fuel injection and a computer to adapt to its surroundings (pressure, temperature, etc.)

That being said, I chose simplicity (carburetor) over complication. It's not right for everybody, but if you know what you're doing, you can make it worthwhile. The deciding factor for me was the 3rd TBI ignition module in a row that fried. I got tired of getting stranded on the side of the road, put a carb on, and I've been good ever since.

If you're only interested in a carb to mount a scoop on the hood, I'm afraid I can't help you. If you ever start having problems with the TBI, and get tired of constantly replacing over the shelf parts because they aren't any good, I can help you out with a parts list and step-by-step process to make the conversion.

-cal30sniper
My problem with the TBI setup is that you can't find parts any more (most of the ones available now are cheap made in China junk). I am now on my third mechanic trying to fix an idle/stalling/check engine light problem and no-one seems to know how to fix it anymore. It stalled today in the line for the smog check.

Hopefully, it will pass and I can finally get the stalling problem fixed. If not, I may consider getting it registered as an antique vehicle. In VA, you can apply for antique plates. You don't have to go through the inspection drill but you can't use it as a daily driver (you have to provide the VIN of another car you use). Other states may have similar programs.

If you got those instructions/parts list, it would be very helpful.

Last edited by mjwadams; 10-01-2011 at 08:24 PM.
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Old 06-09-2014, 01:03 AM   #12
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Re: 88 Chevy 305 TBI conversion to Carb.

Depending of the carburetor available(mine s a holley 2 barrel 8450 from a 79 dodge ramcharger with a 360 engine) the aluminum adapter plate is made, I used the mounting gasket from the rebuild kit as a template , the adapter plate is made out of 1/2" aluminum then the carburetor bolts are drilled and tapped
there was enough clearance for the carburetor barrels to open without touching the intake when opened all the way one hole is drilled thru the plate to attach it to the original intake hole I used a bigger bit and an allen head bolt to make sure is flat on the adapter plate surface, the rest of the install requires epoxy all the way around were the adapter plate makes contact with the original intake leave it overnight to cure and presto

this is what my 88 k1500 looks like now, for the fuel pressure conversion(the original pump puts out 13 pds of pressure a carb would hold of to 9pds of pressure) I left the original pump in and used a Cadillac CTS fuel filter under he hood this filter has 3 lines to it in out and return, so I installed the input line in by the carb the return line bythe carb also)previously they would go behind the tbi and then he output line was hooked up to the carb NO PRESSURE REGULATOR NEEDED) since this filter has a return line all the extra pressure would just return to the tank and would not affect the carburetor.
a hei distributor from a 76 chevy truck was used and THE WIRING HARNESS WAS NOT CUT just tape it correctly and tuck it away on top of the manifold THATS ALL YOU MADE IT CARBURATED NOW!!!!!!!!!!!!!!

Last edited by onemanarmy41; 06-09-2014 at 01:05 AM. Reason: pics
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Old 06-22-2014, 12:13 PM   #13
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Re: 88 Chevy 305 TBI conversion to Carb.

Quote:
Originally Posted by onemanarmy41 View Post
Depending of the carburetor available(mine s a holley 2 barrel 8450 from a 79 dodge ramcharger with a 360 engine) the aluminum adapter plate is made, I used the mounting gasket from the rebuild kit as a template , the adapter plate is made out of 1/2" aluminum then the carburetor bolts are drilled and tapped
there was enough clearance for the carburetor barrels to open without touching the intake when opened all the way one hole is drilled thru the plate to attach it to the original intake hole I used a bigger bit and an allen head bolt to make sure is flat on the adapter plate surface, the rest of the install requires epoxy all the way around were the adapter plate makes contact with the original intake leave it overnight to cure and presto

this is what my 88 k1500 looks like now, for the fuel pressure conversion(the original pump puts out 13 pds of pressure a carb would hold of to 9pds of pressure) I left the original pump in and used a Cadillac CTS fuel filter under he hood this filter has 3 lines to it in out and return, so I installed the input line in by the carb the return line bythe carb also)previously they would go behind the tbi and then he output line was hooked up to the carb NO PRESSURE REGULATOR NEEDED) since this filter has a return line all the extra pressure would just return to the tank and would not affect the carburetor.
a hei distributor from a 76 chevy truck was used and THE WIRING HARNESS WAS NOT CUT just tape it correctly and tuck it away on top of the manifold THATS ALL YOU MADE IT CARBURATED NOW!!!!!!!!!!!!!!
Thank you onemanarmy41! Most of the parts can be found for less than what trying to repair the old TBI. A day out in the garage and your done.
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Old 06-22-2014, 01:08 PM   #14
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Re: 88 Chevy 305 TBI conversion to Carb.

I did the swap last year on my truck.
I had a 87-88 Monte Carlo intake that fits directly on the 87-95 TBI heads with no mods.
I had the hei distributor already. And got a used qjet off a buddy's trans am when I did the swap
For a eddy carb. I modes the throttle bracket to work with what I had.reran a couple of hoses.
I also did a mechanical fuel pump for mine.
So you really need - intake manifold ( preferably a 87-95 style but pre 86 will work with mods)
- HEI distributor
- carburetor
- fuel pump or pressure regulator
And intake gasket kit and some hose,clamps and other bit parts.
Its a easy swap done in a couple hours.
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Old 06-22-2014, 01:08 PM
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