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Converting sbc from carb to tbi?

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Old 05-22-2011, 12:48 AM   #1
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Converting sbc from carb to tbi?

I'm looking at picking up a rebuilt 305 to swap into my 94 s10 4.3. only problem is it's a late 70's motor that is carb'd, is there any way I can convert it to tbi and how would I do that? or is it even possible?
Old 05-22-2011, 08:03 AM   #2
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Re: Converting sbc from carb to tbi?

just need to bolt on the tbi intake or a carb adaptor toss in a few sensors here and thare use the tbi distributer and hook up a computer, and a fuel pump and hammer down
Old 05-22-2011, 10:58 AM   #3
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Re: Converting sbc from carb to tbi?

Basically, the 4.3 sensors and tbi can be reused. you will need a V8 manifold and distributor
Old 05-22-2011, 01:13 PM   #4
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Re: Converting sbc from carb to tbi?

alright, well I already have a spare 305 tbi intake from a 1991 truck, you guys saying I can simply slap that on the late 70s motor and just hook up all my 4.3 stuff?
Old 05-22-2011, 06:45 PM   #5
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Re: Converting sbc from carb to tbi?

yes the only thing is that the four center intake holes are different angle after 87 they are more upright than in 86 older but you can shim them or modify the holes in the intake where the heads of the bolts rest on the intake and change the angle of the holes through the intake with a 3/8" drill bit

use a whole complete ECM and harness from a 700r4 truck full size or s10 or caprice or camaro or firebird etc and the only thing is that i dont know what year and style speedometer you have but you might have an issue there but nothing that cant be corrected with the right stock donor parts and conversion

but if your '94 is still the 4L60E trans then this changes everything and you will need a donor harness from a TBI truck with 4L60E and that combo only existed in 93, 94, and 95 on the full size trucks and i dont know what years in the s series probably 93 and maybe 94 too? maybe 95 also? im not sure what years s series had tbi and 4L40E other than 93

being that you have an early second gen that makes this a bit more interesting and fun hmmm

need an electric fuel tank sender and pump as well from a donor truck and the lines and hoses too for at the TB unit

you can use hose clamps the TBI is low pressure around 12 to 14 PSI

caprices, suburbans, firebirds,camaros, tahoes, jimmys, all pickups, blazers, and some others are good harness and ECM donors '93 to '95 randomly
Old 05-22-2011, 06:52 PM   #6
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Re: Converting sbc from carb to tbi?

Quote: Originally Posted by fast68chevy
yes the only thing is that the four center intake holes are different angle after 87 they are more upright than in 86 older but you can shim them or modify the holes in the intake where the heads of the bolts rest on the intake and change the angle of the holes through the intake with a 3/8" drill bit

use a whole complete ECM and harness from a 700r4 truck full size or s10 or caprice or camaro or firebird etc and the only thing is that i dont know what year and style speedometer you have but you might have an issue there but nothing that cant be corrected with the right stock donor parts and conversion

but if your '94 is still the 4L60E trans then this changes everything and you will need a donor harness from a TBI truck with 4L60E and that combo only existed in 93, 94, and 95 on the full size trucks and i dont know what years in the s series probably 93 and maybe 94 too? maybe 95 also? im not sure what years s series had tbi and 4L40E other than 93

being that you have an early second gen that makes this a bit more interesting and fun hmmm

need an electric fuel tank sender and pump as well from a donor truck and the lines and hoses too for at the TB unit

you can use hose clamps the TBI is low pressure around 12 to 14 PSI

caprice suburban tahoes, jimmys, all pickups, blazers, and some others are good harness and ECM donors '93 to '95 randomly
OP has a 4.3 tbi truck already. His question was about converting a V8 he intends to swap into the truck to tbi.
Old 05-22-2011, 11:31 PM   #7
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Re: Converting sbc from carb to tbi?

Yes my 4.3 is already tbi, but I'm picking up a motor that is carbed. and it's a 5 speed nv3500 btw, should bolt up right?
Old 05-23-2011, 02:12 PM   #8
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Re: Converting sbc from carb to tbi?

Quote: Originally Posted by fast68chevy
yes the only thing is that the four center intake holes are different angle after 87 they are more upright than in 86 older but you can shim them or modify the holes in the intake where the heads of the bolts rest on the intake and change the angle of the holes through the intake with a 3/8" drill bit

use a whole complete ECM and harness from a 700r4 truck full size or s10 or caprice or camaro or firebird etc and the only thing is that i dont know what year and style speedometer you have but you might have an issue there but nothing that cant be corrected with the right stock donor parts and conversion

but if your '94 is still the 4L60E trans then this changes everything and you will need a donor harness from a TBI truck with 4L60E and that combo only existed in 93, 94, and 95 on the full size trucks and i dont know what years in the s series probably 93 and maybe 94 too? maybe 95 also? im not sure what years s series had tbi and 4L40E other than 93

being that you have an early second gen that makes this a bit more interesting and fun hmmm

need an electric fuel tank sender and pump as well from a donor truck and the lines and hoses too for at the TB unit

you can use hose clamps the TBI is low pressure around 12 to 14 PSI

caprices, suburbans, firebirds,camaros, tahoes, jimmys, all pickups, blazers, and some others are good harness and ECM donors '93 to '95 randomly
+1 on the center intake bolts being a different angle, I swapped an '84 350 into my 93 4.3L and had the same prob, ended up going with an edelbrock carb intake and fabbed my own adaptor plate out of an engine hoist plate (can get them at orielleys for about $15 up here instead of paying over $50 including shipping for a carb to tbi adaptor plate just gotta drill and tap holes and such to bolt it in)
other than what he said your only other option would be to swap heads with newer ones i dunno what all would be involved with that though, wasn't worth the time for what i was doing.
Old 05-24-2011, 12:04 AM   #9
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Re: Converting sbc from carb to tbi?

Whoa! carb to tbi adaptor plate? I've never heard of that, any pictures? how'd you go about doing yours?
Old 05-24-2011, 12:09 AM   #10
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Re: Converting sbc from carb to tbi?

its not quite as simple as swapping intakes, the cams were different from carb to tbi so either a chip is needed or the tbi cam is required
Old 05-25-2011, 01:13 AM   #11
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Re: Converting sbc from carb to tbi?

SHiiiittt, what if it has an aftermarket cam, and how would the cam's differ?
Old 05-25-2011, 05:40 AM   #12
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Re: Converting sbc from carb to tbi?

The cam will be fine, none of the 305s had anywhere near a radical enough cam to mess with the tune. Just get either a complete ECM or both chips out of either a full size truck or camaro\firebird with a V8 and manual transmission, the sensors and TBI will all swap onto the new engine pretty easily. This might have been a bit more difficult were it not for your manual transmission.
Old 05-25-2011, 08:29 PM   #13
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Re: Converting sbc from carb to tbi?

how would i mount a throttle body onto a "carb" intake manifold?
Old 05-26-2011, 02:56 AM   #14
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Re: Converting sbc from carb to tbi?

http://www.summitracing.com/parts/TRD-2210/
Old 05-27-2011, 01:43 AM   #15
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Re: Converting sbc from carb to tbi?

Thanks for the link, anybody have any experience with these adapters?
Old 06-06-2011, 11:37 PM   #16
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Re: Converting sbc from carb to tbi?

Quote: Originally Posted by Quincy_4.3
Whoa! carb to tbi adaptor plate? I've never heard of that, any pictures? how'd you go about doing yours?
Sorry, not finding much time anymore with all my summer projects keepin me so flippin busy lol, i'm actually in the process of dropping the tranny outa mine right now to replace the front seal so while its kinda apart anyways i'll try and take some pics of the plate and where I drilled and tapped the holes on it. in hindsight though installing helicoils instead of just drilling and tapping threads to match the tbi bolts would be best if you're doing this with an aluminum intake like I did, would probably give it better clamping force than I ended up getting out of mine
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