TBI to Carb Swap???

[Wild Blue]

I really need my POS TBI gone. I'm a 16 year old kid, I have a 87 chevy with a 350 in it and a 700r4. I've had trouble with the TBI the whole time I've owned the truck and I've had enough. I bought a 010 4-bolt engine from a guy on craigslist. It came with all internals and a .030 bore factory style pistons, pair of heads, brand new headers, oil pan, distributor, etc... Basically i have everything short of a intake and carb. What else do I need? Lock-up kit for tranny? What is a lock-up kit? Will my gauges still work? Thanks for the help and input.

 

[kleedus]

you would be better off trouble shooting and fixing the tbi.

better fuel economy and better drivability

if you own the truck long enough you will eventually kick yourself in the ass for getting rid of it.

tbi is not really that hard to fix what troubles are you having

 

[Wild Blue]

I've been reading up on this swap for a while now and I really don't think it will be hard. I consider myself to be fairly mechanically inclined and i have others for any help I could need. I don't care about milage, can't really get to much worse than 8 mpg. Lol. Carbs are also so much simpler and I don't have restriction on horsepower.

 

[Wild Blue]

So I ended up doing this swap a few years ago and figured some of you might actually want to know how easy this is. Don't get me wrong, TBI is great for your bone stock 305, but for any kind of modified SBC or BBC swap. Don't bother. It truly is junk and you should be ashamed.

First start with tracing all wires attached to your tbi setup back to your cab. then cut each one and cap them off either with electric tape of wire nut. Later you can pull them through the cab and remove them properly, but for now we are just getting them out of the way.

This next part will range widely on what your engine plans are. I ended up dropping in a 454 with mild cam, aluminum intake, a set of cheap long tube headers, and most importantly a new Holley carb. (Don't buy that Edelbrock junk.) BUT if you are just removing your tbi and retaining your current engine; you will just need a carb, intake, possibly a 1-wire alternator, and distributor. I recommend HEI just because they are better and easier to wire. Feel free to argue with me on that. The 1-wire alternator is completely up to you. To me a 3-wire is just as simple.


So after you have your new engine in place or reworked stocker, you can go ahead and finish tbi wire removal. The wires just pull through that rubbery block by the brake booster and back into the cab. Then cut them at their source.
That was good enough for me. Feel free to add to the thread on what you would do differently.

Now you can go to town on your new harness. I used 10 gauge from the hardware store. Buy the stranded wire, NOT SOLID. Just to be safe buy around 40 feet. Better to have leftover that a second trip to the hardware store.


So obviously you will need a basic idea of what a basic engine wiring harness needs to consist of to just the run the engine. See picture attached below. (You may need to download the image to make it bigger.)

So this is what my setup actually ended up being. I ended up running 3 separate harnesses. Don't panic, it's not hard; besides you may only need 1.
The top diagram shows your basic 3 wire alternator on a toggle switch. You can disregard that drawing if you are going to tie it into an ignition switch like the second picture shows.

The second picture shows my whole engine wiring harness. I'm using an HEI distributor; if you aren't just add a coil in there. Everything is tied into a standard hardware store ignition switch. I'm running a switch panel, otherwise I would retain my stock ignition switch. More in depth later.

The diagram to the left on the bottom is for an electric fan controlled via toggle switch and the right being an electric fuel pump also controlled via toggle switch. If you are running your stock parasitic fan, disregard the fan harness. If you are using a mechanical fuel pump or your stock in-tank fuel pump, disregard the fuel pump harness.

Skip 2 Paragraphs if you aren't running those accessories.

If running any kind of external electric fuel pump READ THIS.
I went with a $27 universal unit from Summit.
https://www.summitracing.com/parts/atx-e8012s/overview/
This pump works great and is very simple to wire. I also installed Summit's fuel pump relay kit, but you don't necessarily need that so I won't go over it.
The pump just has a black and red wire hanging out. Run your red to the toggle switch and positive battery terminal. Black from the negative battery terminal to the other pole on the toggle switch. You now have fuel.

Next to supply you air flow. The electric fan is the same as the fuel pump. Red to toggle switch and battery, and black to toggle and battery. You now have heat dissipation.

Back to the engine harness. All you have to do is copy the diagram. Feel free to add inline fuses if it makes you feel safer.

Feel free to ask any questions or criticize. I will respond. I know i lack pictures, but just ask and I'll upload.

Also through in a picture of my 454 and new engine... LS 5.3 with 76mm turbo. http://www.gmsquarebody.com/forum/images/smilies/party36.gif

 

[otter5555]

i MUCH prefer any carb over any injection. carbs are dirt simple and always work. both my square bodies are running 350's with Edelbrock Performer intakes and 600 CFM CLASSIC HOLLEY CARBs.

both avg 17.5-18 mpg in daily driving.

i'm gonna start an '87 k20 build in the fall and the FIRST thing i will do is get rid of the
TBI

 

[Wild Blue]

I like fuel injection. Just not TBI. Very in efficient and like you said, 17-18 MPG; that's probably better than any TBI setup. That's why I'm doing the turbo LS build. I'm going to be pulling my 5,000 lb boat most weekends now and can only afford to fuel one of the big blocks lol. I'm hoping to get around 14 MPG with the boat on. Going to be starting with 7 pounds of boost. Should be making around 450-500 rwhp. http://www.gmsquarebody.com/forum/images/smilies/patriot.gif

 

[eric 87]

So I ended up doing this swap a few years ago and figured some of you might actually want to know how easy this is. Don't get me wrong, TBI is great for your bone stock 305, but for any kind of modified SBC or BBC swap. Don't bother. It truly is junk and you should be ashamed.

First start with tracing all wires attached to your tbi setup back to your cab. then cut each one and cap them off either with electric tape of wire nut. Later you can pull them through the cab and remove them properly, but for now we are just getting them out of the way.

This next part will range widely on what your engine plans are. I ended up dropping in a 454 with mild cam, aluminum intake, a set of cheap long tube headers, and most importantly a new Holley carb. (Don't buy that Edelbrock junk.) BUT if you are just removing your tbi and retaining your current engine; you will just need a carb, intake, possibly a 1-wire alternator, and distributor. I recommend HEI just because they are better and easier to wire. Feel free to argue with me on that. The 1-wire alternator is completely up to you. To me a 3-wire is just as simple.


So after you have your new engine in place or reworked stocker, you can go ahead and finish tbi wire removal. The wires just pull through that rubbery block by the brake booster and back into the cab. Then cut them at their source.
That was good enough for me. Feel free to add to the thread on what you would do differently.

Now you can go to town on your new harness. I used 10 gauge from the hardware store. Buy the stranded wire, NOT SOLID. Just to be safe buy around 40 feet. Better to have leftover that a second trip to the hardware store.


So obviously you will need a basic idea of what a basic engine wiring harness needs to consist of to just the run the engine. See picture attached below. (You may need to download the image to make it bigger.)

So this is what my setup actually ended up being. I ended up running 3 separate harnesses. Don't panic, it's not hard; besides you may only need 1.
The top diagram shows your basic 3 wire alternator on a toggle switch. You can disregard that drawing if you are going to tie it into an ignition switch like the second picture shows.

The second picture shows my whole engine wiring harness. I'm using an HEI distributor; if you aren't just add a coil in there. Everything is tied into a standard hardware store ignition switch. I'm running a switch panel, otherwise I would retain my stock ignition switch. More in depth later.

The diagram to the left on the bottom is for an electric fan controlled via toggle switch and the right being an electric fuel pump also controlled via toggle switch. If you are running your stock parasitic fan, disregard the fan harness. If you are using a mechanical fuel pump or your stock in-tank fuel pump, disregard the fuel pump harness.

Skip 2 Paragraphs if you aren't running those accessories.

If running any kind of external electric fuel pump READ THIS.
I went with a $27 universal unit from Summit.
https://www.summitracing.com/parts/atx-e8012s/overview/
This pump works great and is very simple to wire. I also installed Summit's fuel pump relay kit, but you don't necessarily need that so I won't go over it.
The pump just has a black and red wire hanging out. Run your red to the toggle switch and positive battery terminal. Black from the negative battery terminal to the other pole on the toggle switch. You now have fuel.

Next to supply you air flow. The electric fan is the same as the fuel pump. Red to toggle switch and battery, and black to toggle and battery. You now have heat dissipation.

Back to the engine harness. All you have to do is copy the diagram. Feel free to add inline fuses if it makes you feel safer.

Feel free to ask any questions or criticize. I will respond. I know i lack pictures, but just ask and I'll upload.

Also through in a picture of my 454 and new engine... LS 5.3 with 76mm turbo. http://www.gmsquarebody.com/forum/images/smilies/party36.gif

Thanks. The wiring part I may get fancy and spend money on a new harness as well. I have shot the parts gun at my 305 TBI I bought 10 months ago. And when the engine is running for a stock (we know no HP) it really is feeling better about itself. But then it idles low and shuts off. Then high as in 1800-2200. Then going down the road out of the blue it shuts down completely. I replaced everything and rebuilt the TBI and regulator. New dizzy all new sensors and double checked them with multimeters. Everyone says to keep the TBI. But I have invested 550$ in two weeks just doing that and still....I can't drive and feel confident I will get home. So I drive my others.
I think I can get a proper bolt hole after market Intake and carb and distributor and fuel pump and be under 2000. I may or may not lose a mile per gallon but at least I can drive it!

Every time I ask what are the best parts or anything related not just here but everywhere I get the KEEP THE TBI. If it were stand alone maybe but not with the first year computers and all the sensors. I replaced it all and it still isn't right. Color me frustrated.

 

[eric 87]

Hello Fellas and any Ladies that may be here.
I got my shipment of parts from Summit and I went and bought what I hope is all the incidentals I will need locally. So the TBI to carb swap is underway. I have everything taken apart and the intake is still sitting in the truck with the fuel lines attached being the last thing.
I was thinking before pulling the lines off and lifting the intake out....now would be a good time to figure out a way to completely eliminate the computer from the truck. SO here is my NEW question. I looked through forums in the modification section but didn't find exactly what I am after.
I know that many keep the pumps in tank and use the regulator which I was intending on doing. Splicing the purple wire in the four wire plug to dist and connecting to tach port on new HEI so computer will see signal for fuel pump.
However.....is there a way to just splice into the wire at the dash switch or to the wire going to pumps with a switched hot wire to supply power with key on and then be able to eliminate the computer wiring altogether so the check engine/SES light will not be lit from all the sensors being unplugged?
From what I understand the computer on an 87 only controls the engine management of the TBI system and fuel and none of the gauges.
I will keep the wiring for the computer in the truck but hide it should someone down the road choose to put it all back. If this project doesn't prove to be beneficial I will cut bait as it is said and sell it. And I will offer all the TBI parts I am taking off it now to the new owner in the event they want to chase the electrical goblins.
My wife and I love the truck but she said if it isn't dependable it goes and I can't agree more. It quit on her after all the money spent on the TBI.

Any ideas on the best way to go about the fuel system would be great.

I was thinking eventually to replace BOTH in tank pump/senders with non pump senders. THen run this 3 way valve,

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Wire the dash switch to switch the gauge/sending and the tank switch. Eliminate the return line altogether or keep and let it go to one side off the regulator. But I would go with a low pressure fuel pump just in front of the switch valve so it can be used for both. I had thought of two electric pumps much like the current set up but with less pressure then eliminate the new pressure valve.

My question is shouldn't I be able to wire the fuel system this way and where would the best source of switched power be. ALso intend on adding the inline safety shut off in case of low oil or accidents.

I have gone down many rabbit holes in the forums looking at all sorts of things and not getting work done on mine.

I do appreciate all the advice and support so far in this journey that I didn't really want to undergo in regards to TBI vs Carb. I have had both and like both. TBI is great on cold mornings. But I never intend on living in a house without a heated garage again in my life. If so....well....nope not gonna do it! And I hope to move where mornings aren't that cold!