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| Username | Post: 92 2500 TBI to CARB swap questions... | |
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Bowtie2500 Forum Newbie Posts 51 |
 07-22-12 01:31 PM - Post#2250904
Whats up chevytalk. i just picked up a 92 silverado 2500. The motor is old an tired and the wiring is just completely molested.. it still runs and operates but im going to be pickin up another tbi 350.. and i AM going to do a carb swap so plz no trying to convince me otherwise.. i understand i need a Carb,intake manifold, distributor, and fuel pressure regulator.. My trany is a 700r4 an is controled by cable. obv i would be eliminating the ECM+ harness. so my questions are what els will i need? and is my cluster wired into the engine harness?...My main concern is what wiring needs to be done. Do they make a new harness you can buy for the starter, alternator, etc...plz any help or a link to a write up thread would be great! Thanks, corey.
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navygunner08 Silver Supporting Member Posts 611 
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07-22-12 01:57 PM - Post#2250917
I dont think they make any harness like your asking about. But one thing that you will need is a tach signal if you have an RPM gauge on your dash. this is normally taken off of the white wire coming off of the coil (there will be an external hook up on the wire).
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 02:10 PM - Post#2250919
So would i have to run power wires to the alti? the starter ect?
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 02:34 PM - Post#2250928
This swap shouldnt be all that hard.. i jus need to know how to get power to everything an where its gana come from.. if anyone knows or has a write up DIY link i would apprichiate it.
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 04:56 PM - Post#2250960
Nobody has any information on this or wants to give their input? i was told there are alot of smart ppl on this site. lets see the guru's chime in. i need help plzz!
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drifterdude Frequent Contributor Posts 1282 |
07-22-12 06:50 PM - Post#2251004
There are alot of good smart peeps on here but we dont all ride the forum all day long. Most (99%) keep the TBI for simplicity and reliability and they can support a good amount of power before needing to come off due to restrictions. Alot of people other than interior swaps stay away from molesting the truck. Anyways as stated tach signal wire has a tap in it you can use. Depending on the carb there are plenty of adapter brackets out for the TV cable linkage to the trany. You got it all right as far as engine parts go though. being its a 92 the speedo is ran from the speed buffer in a white case behind the glove box. If you do not want to switch to after market you will need to keep that as well. If you got a oil pressure gauge as most or all do the sending unit is on the back of the block by the drivers side head in a brass fitting. Its pretty much right at the corner of the intake back there. You can fallow that wiring to where it goes and chop it and re run it after the harness is out. The water temp sending unit is in the drivers side head for the guage as well so you know what wiring it is to keep the cluster going. If you got the money though I would recommend just pulling the cluster and laying a few sheets of carbon fiber or whatever you want and take a hole saw to it and make a custom cluster with new sensors and units to match. It would prevent hack wiring to keep the cluster going and would look better IMO. when you start removing wiring your dash ground is going to the bracket that holds the hood release lever. Alternators charge wirie goes up the distribution block on the passenger side firewall and to the battery from there. If you go under the truck the solenoid feed from the ignition on the starter is a purple wire it should go all the way up the harness to the driver side. You can continue to use it. Rest of the starter im sure you know is just straight from the battery and grounds to the block when bolted on. When re wiring I would recommend increasing the size of the charge wire from alt to distro block and from the distro block to battery. the 2 grounds on the thermostat housing and intake wont need to be kept if your taking out the ECM.
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 07:01 PM - Post#2251007
well thank u that helps.. my buddy has a edelbrock carb an the correct disi.. id like to keep the stock cluster. right now i jus have to get a motor in WITH a carb swap because i spun a bearing in my DD (00 celica). i have only worked,and built hondas this is all new to me. i have been told by some local chevy guys that its not that bad of a swap. i am trying to learn about american cars an v8s so i jus need to have info on how to wire everything els.
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 07:06 PM - Post#2251009
that really does help. it doesnt seem that hard to do this swap.. i know some one who can tune carbs so it will run fine. but i need input from others also as im sure u have all been there.... like i said this truck has jus been all shake tree mechanic molested... i pulled out about 6 lines today that were jus sitting there... along with the charcole canister... break lines fuel lines, trany cooler lines,and ac lines. really this wiring harness is a hazard. and i need expirence with carbs
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someotherguy Moderator Posts 23381 
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07-22-12 08:03 PM - Post#2251030
I think the term you're looking for is "shade tree" and it sounds like it's going to continue to be a victim of it. The original TBI system really isn't complicated and it's not that hard to get a replacement harness in there to get all the original parts working correctly again. You can take that from someone that has been there and brought back trucks from death's door... But you said don't try to convince you otherwise, so... Richard
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 08:46 PM - Post#2251045
how would it continue to be a victom of it? are u judging somebody threw a computer? well haters will hate.. i have done plenty wrenching for a long time. so take ur BS elswhere.. nobody likes flakey disrespectfull ppl. anyways thanks to the rest of you usefull ppl.. i apprichiate the help... an FYI this tbi setup is the worssse engineering i have ever seen... so u can keep ur little pride that u have for such a rediculous design...
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Bowtie2500 Forum Newbie Posts 51 |
07-22-12 08:49 PM - Post#2251047
P.S not 1 word u said helped anything.. this thread is for how to convert from tbi to carb.. not for u to put in ur 2 cents u have about the tbi... i have been around the most advanced FI setups which are from honda so for u to say TBI is worth even talkin about is a joke to me bud..
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drifterdude Frequent Contributor Posts 1282 |
07-22-12 10:24 PM - Post#2251057
not going to try to change your mind but will give you some info just on the easy of the TBI. With that motor out the harness is realy easy to repair. I recently restored my harness took no time realy. Only factory wiring is minimal. ill give you an example based on a 4x4 which has just a few more than a 2wd. Wiring to 4x4 switch and actuator, speed sensor, coolant temp sensor (dash) another for the ECM, Anti locks if you keep them, injectors, 2 grounds on the intake and thermostat, a knock sensor, a pigtail for AC and another for the altenator, one to the TPS, one for the IAC, one for the MAP and one for the oil sending unit, also for the ICM in the dizzy and from it to the coil. Minimal realy compared to anything modern. The TBI runs forever is maintained like it should be. the TBI is realy a carb just instead of adjustments and a bowl of fuel it meters itself and flows. If the sensors are good and engine good it fires and runs regardless cause there is no tune to do. TBI can support 400hp +. One other tidbit as well. Dont not try to put on a CAI as the stock through fender setup can flow enough for a big block without issue and is colder and better than a CAI for a 350. The reason for the lack of info on carb swap is really the lack of carb swaps done due to the reliability and ease of the TBI. Even jeep owners who put 350s in the jeeps try to maintain the TBI. Same reason TBI has been increasing in aftermarket for bolt on apps for race motors. Carb is not on its way out and is still good but TBI is becoming more mainstream on performance builds and older cars for ease of use. most common problem with a TBI motor is just a bad coolant sensor by the intake. Next is wrong or bad thermostat and or EGR. Bad fuel pump happens about as much as any other car. Im not going to push it on you just wanted to give you info since you are new to this as you state with V8s and domestic cars/trucks. this particular TBI setup is one of the best to work with if not the best. And if you look at my signature to see what ive done to mine its still on TBI and that list is not all it has. I drown my truck in the pits frequently and also use it as a Daily driver. I get average of 12-15mpg on it and have never had a issue that was not something caused by the PO playing with something he though he could improve or from not paying attention to the truck itself.
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sgian Valued Contributor Posts 4438 
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07-23-12 04:23 AM - Post#2251090
Nobody said the TBI system was advanced, LOL. And it isn't very powerful either. What it is, is simple and reliable. Having gone from carbed vehicles to TBI vehicles myself, the only reason I can see for getting rid of the TBI system is to make it more powerful. And to do that you need to change the heads, along with the exhaust system. The TBI heads are of a swirl port design. The swirl port increases low end efficiency at the cost of moderate to high end air flow. Nearly any small block chevy head design is better for flow than the TBI heads. Just find something with around 64 cc combustion chambers and you'll be good. The vortec heads are good, but the carbed intake for vortecs is more expensive and the intake gaskets have a higher failure rate due to the distance between the bolts in the front and back. Otherwise, get heads for a 350 from 86 and earlier with 64 cc heads. Many will be 76 cc heads, which will make a lower compression ratio and defeat the purpose of getting a carb for more power. If you stick with
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sgian Valued Contributor Posts 4438
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07-23-12 04:35 AM - Post#2251091
Sorry, my cat entered my post midsentence and I'm having trouble editing it... If you stick with TBI heads for some reason, the intake manifold will still be unique for the TBI system even with the switch to carbs. That is because on TBI heads, the middle four bolts are at a different angle than in earlier years. They make carbed intake manifolds for TBI heads, or you can grind out the holes and risk bending and breaking the bolts due them not seating right on the manifold. Your best bet for information is a google search. There are guys who come by in this forum who have done this switch, but they aren't regulars. Or you might try the Performance section.
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someotherguy Moderator Posts 23381
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07-23-12 04:36 AM - Post#2251092
how would it continue to be a victom of it? are u judging somebody threw a computer? well haters will hate.. i have done plenty wrenching for a long time. so take ur BS elswhere.. nobody likes flakey disrespectfull ppl. anyways thanks to the rest of you usefull ppl.. i apprichiate the help... an FYI this tbi setup is the worssse engineering i have ever seen... so u can keep ur little pride that u have for such a rediculous design... Actually, it's you that is judging me by saying I'm a "hater" and that I'm "flakey" and "disrespectfull" - I base my opinion of that your truck is a victim because of what I've already read, and that it will continue to be one because your willingness to hack it and immediate unwillingness to listen to any other opinion that might net you a better result.
P.S not 1 word u said helped anything.. this thread is for how to convert from tbi to carb.. not for u to put in ur 2 cents u have about the tbi... i have been around the most advanced FI setups which are from honda so for u to say TBI is worth even talkin about is a joke to me bud.. If your experience level is so high I wonder why you're here asking for help? Most of us here get along great and exchange ideas and help on a regular basis without any drama; new guys that show up with a chip on their shoulder rarely last. And yours was announced in your first post. Richard
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Allan In NE Contributor Posts 898 |
07-23-12 04:57 AM - Post#2251098
Just for what it's worth: The biggest advantage of computer controlled fuel delivery is that it stops the burning of valves and extends engine life. The horse and carriage had this advantage also. Allan
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Bowtie2500 Forum Newbie Posts 51 |
07-23-12 06:14 AM - Post#2251119
thanks guys for the info. seems nobody cares to much for carbs an i know i can repair the harness i have i was fallowing alot of wires yesterday an it looks fairly easy... i see alot of ppl swapping to carbs, even on LS series engines.. sure its not the most efficiant all i want is expirence with them.. as stated i can make power with the tbi setup i understand an u have been to a site an done some reading on their "chips" an live data logging hardware. then that takes even more cash to have it tuned an i would need a REAL wide band.
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Bowtie2500 Forum Newbie Posts 51 |
07-23-12 06:17 AM - Post#2251122
Also i do want more power i plan to get a set of headers, some heads an a cam eventualy... i wanted to get a better running tbi swapped with a carb in as of right now.... i live in New England an cant find much for engines around.
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Bowtie2500 Forum Newbie Posts 51 |
07-23-12 06:45 AM - Post#2251127
not going to try to change your mind but will give you some info just on the easy of the TBI. With that motor out the harness is realy easy to repair. I recently restored my harness took no time realy. Only factory wiring is minimal. ill give you an example based on a 4x4 which has just a few more than a 2wd. Wiring to 4x4 switch and actuator, speed sensor, coolant temp sensor (dash) another for the ECM, Anti locks if you keep them, injectors, 2 grounds on the intake and thermostat, a knock sensor, a pigtail for AC and another for the altenator, one to the TPS, one for the IAC, one for the MAP and one for the oil sending unit, also for the ICM in the dizzy and from it to the coil. Minimal realy compared to anything modern. The TBI runs forever is maintained like it should be. the TBI is realy a carb just instead of adjustments and a bowl of fuel it meters itself and flows. If the sensors are good and engine good it fires and runs regardless cause there is no tune to do. TBI can support 400hp +. One other tidbit as well. Dont not try to put on a CAI as the stock through fender setup can flow enough for a big block without issue and is colder and better than a CAI for a 350. The reason for the lack of info on carb swap is really the lack of carb swaps done due to the reliability and ease of the TBI. Even jeep owners who put 350s in the jeeps try to maintain the TBI. Same reason TBI has been increasing in aftermarket for bolt on apps for race motors. Carb is not on its way out and is still good but TBI is becoming more mainstream on performance builds and older cars for ease of use. most common problem with a TBI motor is just a bad coolant sensor by the intake. Next is wrong or bad thermostat and or EGR. Bad fuel pump happens about as much as any other car. Im not going to push it on you just wanted to give you info since you are new to this as you state with V8s and domestic cars/trucks. this particular TBI setup is one of the best to work with if not the best. And if you look at my signature to see what ive done to mine its still on TBI and that list is not all it has. I drown my truck in the pits frequently and also use it as a Daily driver. I get average of 12-15mpg on it and have never had a issue that was not something caused by the PO playing with something he though he could improve or from not paying attention to the truck itself. Thank you... seems nobody seems to care for carbs anymore ha, i dont have to pass emmisions here since its a 92.. if i ended up keeping the tbi the egr has to go.. the truck is burning alottt of oil an spittin an missin. 210k an its tired.. so i supose carb swaping would jus cost more money... but keeping the tbi could cost more aswell..
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355Cheyenne Senior Member Posts 3743 
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07-23-12 07:43 AM - Post#2251153
i understand an u have been to a site an done some reading on their "chips" an live data logging hardware. then that takes even more cash to have it tuned an i would need a REAL wide band. I just sold my 88 a couple years ago, I would have kept it but I had another kid and needed some cash more than the truck. I built that to be my toy mudder with 35x12.5x15 BFG M/T. The motor I built for it put out a decent amount of power, I could easily do a 4x4 burn out to put things into perspective. This was all done on the TBI platform and as far as "tuning" I was able to get into my own custom tuner for under $40. I went on ebay and bought some eproms and a programmer and an eraser. Then I used free software tools that are out there. Point being is that it need not be expensive if you don't want it to. The motor I built was a 5.7 bored 30 thousandths over so it was a 355. I had a sum k1102 cam, Edlebrock performer TBI intake. Holley 650? cfm TBI. Headers, some mods in the valve train with chromemolley lifters and a bunch of other junk. I think I built that thing back in 04 or 5 for under $1200 (including machine work). TBI isn't a wonderful magical super thing but it blows the pants off any carb in terms of reliability and drivability. TBI will trim fuel so you can run it in -50F up to 110F + or from as low as florida to the the top of the rockies. A carb would require manual trim work or re-jetting in a lot of these cases to run correctly. The properly setup TBI engine will wear significantly less and last longer. Slapping a carb on there is a false economy. We have helped people in the past switch to carb. I think I have seen it done a hand full of times here over the last decade, the difference is they weren't as impatient.
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Bowtie2500 Forum Newbie Posts 51 |
07-23-12 04:32 PM - Post#2251345
its not really that im impatient, the vehicle im driving spun a bearing so i only have so long.. i picked up the truck for $500. i realize i need a motor in it asap. and i jus wanted to learn more about them an go old school i there are plenty of ppl running carbs out there, and even more with efi an i know how efficiant it is. i still plan to do it in the near future.. jus gana do some research an learn about these pushrod motors first.. my apologies to the guy i went off on. i was told he is a very helpful guy an knows the sh*t by a local chevy guy.. i apprichiate the advice
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someotherguy Moderator Posts 23381
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07-23-12 04:51 PM - Post#2251356
No worries. Believe me, a while back I asked about the same conversion and all it would entail, and decided in the end it wasn't for me. Mostly because I was looking to build more power but it would have ended up being something that would no longer pass inspection here in TX. Our search engine takes a little getting used to, but you can find lots of info about what you're asking - if you go to the Search button there are some tutorials on using it, and also I give a quick description of Advanced Search if you check our FAQ post at the top of this forum. Richard
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Bowtie2500 Forum Newbie Posts 51 |
07-23-12 05:27 PM - Post#2251372
I have used the search engine here an cant really find any write ups on this.. is there any on here? if not howcome nobody has done one? i find alot of ppl use the holley tbi but its pretty costly..
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Bowtie2500 Forum Newbie Posts 51 |
07-29-12 10:55 AM - Post#2253339
Well, i still have found any complete write ups on carb swaping from TBI..but have dont even more research and learned once everything is mechanicly converted its just getting some of the vitals to the cab..There are many many ppl using carbs today and ppl will do as they want even if its taking a step back in technology.. Is there anyone here that is interested in doing a writeup on carb swaps?. i think it should be done.
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Astro88 Forum Newbie Posts 33 |
07-31-12 02:38 PM - Post#2254236
Well, i still have found any complete write ups on carb swaping from TBI..but have dont even more research and learned once everything is mechanicly converted its just getting some of the vitals to the cab..There are many many ppl using carbs today and ppl will do as they want even if its taking a step back in technology.. Is there anyone here that is interested in doing a writeup on carb swaps?. i think it should be done. My buddy and I did this to his 93 2500HD, as he wanted reliability (the ECU had already killed 3 rebuilt by the dealer transmissions). This is his work truck, that sees everyday use, and might be driven 200 or more miles in a single day. Since you're going to keep the 700R4 (we switched to a THM400), you'll need to get this switch from the dealer, part #8642473 . It's an 89 Camaro 4th gear pressure switch, that you'll need to get 4th gear to "lock up" over 45mph. The original switch is NC (normally closed), while this switch is NO (normally open). You'll also need add a power wire to 1 side of the brake light switch, and an output wire, that will feed the trans, so it can lock up, or unlock when the brakes are applied (no computer needed), and then add a ground wire to the black wire in the connector at the trans. Also, before you go clipping all of the wires from the ECU, you're going to need a couple of them. These are the temp sensor, tach signal wire, and a power wire to the ignition coil (switched power thru the key). After that, it's just a matter of swapping the intake manifold, add a carb and use an HEI distributor from a 76 to 85 chevy truck, or an Accel blueprinted unit. This set up makes a very good bullet proof combo. My friends truck has well over 125K on it in the last 7 years, and is only being temporarily taken out of service for rust repair work. We'll probably do a tune up to it while it's down, but not much else. The trans switch mod is also bullet proof, as I've ran it for almost 10 years in my 85 V8 Astro.  |
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Bowtie2500 Forum Newbie Posts 51 |
07-31-12 03:33 PM - Post#2254255
wow, thank you thats all i needed. im glad somebody has come threw for me. doesnt seem all that hard. 
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Bowtie2500 Forum Newbie Posts 51 |
08-01-12 09:02 AM - Post#2254486
P.S- i also need a bracket for the TV cable. i just learned that lol. maybe you should do a complete write up on this procedure?
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Astro88 Forum Newbie Posts 33 |
08-01-12 04:03 PM - Post#2254641
P.S- i also need a bracket for the TV cable. i just learned that lol. maybe you should do a complete write up on this procedure? The problem, is that I/we did the conversion back in 2007, and I've slept since then. Most of the stuff we did, had been done on previous cars we built, so it wasn't a big deal to do. We also don't have emissions testing in this state, so it doesn't see a tester. Like I said before, we also converted the trans from a 4L80E to a Turbo 400, as we wanted to do heavy hauling and trailering with that truck. The truck itself had 272K on it, and was misused and abused, and put away wet (it was a former Texas farm truck). Very used up, but it was also a heavy duty 3/4 ton truck (8601 rating). He bought it for scrap price (500 without a motor or trans) so we had nothing to loose. But I may end up doing a write up, IF I can't get the 88 fixed. 
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Bowtie2500 Forum Newbie Posts 51 |
08-01-12 06:06 PM - Post#2254692
Cool! i apprichiate the help! thats alotttt of miles, mine has 212k an burns oil like crazy.
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