TBI to carburetor

[tylerlayne]

Can a TBI engine be changed over to a carburetor engine by just adding a fuel pump and changing the intake? Not wanting to do this but someone tried to do it to a engine I just acquired. If it can be done other than what I just mentioned what else needs to be changed? Thanks

 

[jkeaton]

What year truck?

 

[Ironhead]

These questions make me want my old 65 C10 back. It had only four wires to the engine: Ignition to distributor, battery to starter, ground strap, and wire to alternator. So simple. It ran good, got 14 mpg, and was sooooo easy to work on.

Now, just to change to a carb, we gotta think our way through sensors,, computers, and miles and miles of wires.

 

[jkeaton]

Agreed ^^. I know there is more to it than just changing the carb and intake, but going from an OBD1 to carb is easier than going from OBD2 to carb. Really don't know why you would want to though. That's a big step backwards IMO.

 

[JScott23]

First you are going to need a HEI distributor, intake, and a fuel pressure regulator. (with a return) Factory TBI pumps send 10-12 PSI. Its pretty important to keep the return fuel line because your carb can only handle 6psi max. The pump will want to throw 10-12 at it. The regulator will throttle it down to 6 psi, but you will burn up the regulator if you have 10-12 PSI getting crammed into it with no way to release the excess fuel back into the tank. (Ask the Summit/Jegs tech guys) You mentioned your truck was a TBI, so i'm assuming its a 1995 or newer, but if its a 1996 and later, it will have the Vortec motor, and Vortec pumps send upwards of 40psi. If your truck is a 1996 or later it's not a problem, you will just need to install a 88-95 TBI fuel pump (10-12 PSI pump)

Now for the transmission: (IGNORE IF YOU HAVE A 700R4 or NV3500/4500)
- Again assuming the truck is a 95 and earlier, if it has the 4L60E/4L80E. you should be able to run a TPS sensor on your carb and that will allow the PCM to shift the trans. If it's a 96 and later 4L60E/4L80E you will certainly need an aftermarket controller. Unless you really know how to make all the wiring work. Which I do not.


I have put a carb'd motor in my 94 (former blown up 6.5 truck) Didn't want to spend cummins money and had a bad IP and bad block so figured, screw it why not just run a carb'd 350. However I would really think about some of these things first.....


Do you have emissions? Retrofitting the truck will certainly prevent it from passing any required inspections.

What is your mpg? I would expect a 2mpg drop by switching to carb. At least that's the approximate loss in fuel efficiency that I'm experiencing in my application. (1 Ton CCLB -2WD)

Do you drive this in the winter? Supposedly carbs are a PITA with cold morning starts... I haven't had mine long enough to know.. However I do know that my electric choke makes it idle very fast in the cold and it will actually make the engine run on after I turn it off when its idling that fast. #carbprobs

What are you attempting to achieve? If you think the carb will wake up an old worn out motor and bring you power where power doesn't exist, i'd think again. Many guys say TBI's can be tuned to surpass the power of a carb. I would take my Edelbrock carb over a stock TBI power wise, however you'll pay for it in fuel mileage. Supposedly they can tune up these TBI's to exceed the power of a carb while keeping the TBI fuel efficiency. Not exactly sure how all of that works. If you are just trying to replace a blown engine on a budget and don't care, I would see if you could keep the TBI personally, and maybe look into some alternative options to boost the TBI power. Those TBI's can sit for years and start right up, but if you want to give the carb a shot, rock on. I'm not going to hate on carbs and say don't do it, you just need to know the pro's/cons. Remember my engine/carb are all BRAND new. So I haven't experienced any of the down the road issues.


From someone who's done it, I'm actually planning on switching to and aftermarket EFI setup to see if I can add a little more power, tuneability, and fuel mileage. No complaints on the carb, but I think EFI is probably a better choice for daily driving. I wouldn't think twice to put a carb in a hot rod, however It has flaws for a daily driver. If you do it, I would run a mechanical choke.. I have no control over my electric one and it high idles whenever it wants and like I mentioned earlier, the high idle causes some run on after I turn it off. I basically have to make sure the choke is not on when I turn it off.

 

[TylerZ281500]

obd1 and obd2 to carb is the same thing if you know what your doing. id suggest not. if it cam ewith the truck or is prupose built past the point of dealing with efi then fine but on a daily its useless. constant tuning is needed on a carb where as efi does all its modification itself. tuning obd1 and obd2 is a learning curve but is a great learning experience. it also teaches you how to build an engine properly based on efi requirements and not "slapping" things together.

carbs are cool if used properly and maintained

tbi is cool if you have the knowledge to understand it

if you cant figure out tbi dont even attempt vortec despite its less than finicky operating system.

for a electric trans you need tps and rpm signal; sent to the computer which means you still have to retain all the old wiring and not hack it up hopefully.

fuel mileage wont go up, power wont go up unless you think seat of your pants is sceintific, cold starts are a pain.

fuel regulators are needed

etc.

 

[tylerlayne]

My truck is a 88 and the engine is a 92. Not wanting to convert to carb,just wondering why the guy who owned the engine before me said he could never get it to run right in his truck. His truck was a tbi truck and he tried to convert it to a carb. Want to be sure the reason he was having problems was because he tried to make it a carb engine in a tbi truck.

 

[TylerZ281500]

his trans is mechanical, 88-92 is probably the easiest to convert to carb, he probably just had no inclination what he was doing to the tbi and thought it was a good idea to convert it.

 

[tylerlayne]

That is what I was thinking. Years ago you could put any engine you wanted in cars before everything was computer controlled. I used to work at a speed shop as a body man and painter. The guys I worked with put a built 454 in a mustang for a customer. We Narrowed and tubed the rear end and built a full roll cage in the car. Bad ass chevy powered mustang.