Change from tpi

i have a 1994 chevy silverado with 350 and fuel injection/tpi. i want to get rid of the tpi and put on my 4 barral holly and performance intake. my questions what changes have to be made to the fuel tank /pump/fuel line/. and how to keep egr system in compliance

Obviously you’ll need the parts associated with the carb and fuel delivery system that you probably already know about. You’ll also need a new intake manifold, a new wiring harness and a standalone computer to run the transmission since the original computer is going to be looking for sensor inputs from the TPI setup that you will be ditching. You’re in for a lot of work and a lot of money, and at the end of the day depending on where you live, it’s likely to be illegal.

When you change any part of the system the truck will be out of compliance.

Such a retrofit would require dropping the tank and replacing the fuel pump and related hardware with a basic sock and tube and connecting a simple 4 to 5 psi electric fuel pump in the fuel line. A 1981 or earlier distributor must be installed and you might want to put a quick connect on the catalytic converter. It will be getting replaced often.

Also, what transmission is in the truck? If you have the “E” model transmission it must be replaced with an earlier model.

If you have emission testing where you are you can’t remove the TBI and replace it with a carburator. The TBI and it’s related components are part of the emissions control system. If the vehicle was only for off road use and not driven on public roads then you could do it.


TBI (Throttle Body Injection) or TPI (Tuned Port Injection)? I believe a 94 Silverado came with TBI.

If it’s more power you are looking, the cam and heads should be replaced. The stock heads are pretty restrictive. I looked into this for a 305 (L03) V-8 in my 93 Caprice. I decided to leave well enough alone. Here is a link to a site I came across. I didn’t order from them, so I can’t vouch for them.

Ed B.

If you are looking for more power sell the intake and carb and get a good high performance TBI set up with matching heads and cam.

i am not looking for extra power/performance. my truck is still running like crap. if i change to the old school carb and intake i might get the truck to idle and run correctly.

There isn’t that much involved with TBI, so proper diagnostics should find the problem. Have you at least pulled codes?

To convert to old school, you need more than just a carb and intake. You also need a distributor and a carb-friendly fuel pump.

You could keep the TBI fuel pump in the tank, but the wires need to be disconnected for the pump so it will not activate. That pump is capable of up to 100 psi, and that will blow out the carb. An electric fuel pump for about 5 psi output will need to be installed to feed the carb.

You will also need an HEI distributor or older-style Mallory points distributor. The TBI distributor has a special sensor for the computer to control ignition timing. It can be adapted to a stand-alone ignition system with electronic-controlled advancing, but an HEI distributor drops right in and handles all of that for you. And you only need 12V power to run it. A Mallory points distributor is also a drop in, but requires a ballast resistor to prevent points burn out.

You might be disappointed if you spend $1,000 on parts and work 3 weekends on the retrofit only to find that the engine has a bad valve, @Mr Bond. The TBI system is simpler than a carburetor.

2nd that. Fix what’s wrong. Usually folks want to spend 2k adding FI to truck. Not remove it. It should work fine. Nice idle, good driveabilitupy, probably better mileage than carbed setup? Oh well.

ok, it sounds like too much trouble to install an old 4 barral carb, so i will not try.

Truck runs like crap? Bad? So it sounds like something is way off, not just a little? And u blame FI system? Poor idle, running rich? Worn throttle shafts? Touchy injectors? There are 2 u know? Bad O2 sensor? Fuel pressure regulator? Leaky intake gasket? But u think tossing all the FI stuff is easier than replacing it with OLD crappy 4bbl intake and worn out carb?

over the last eight months i have replaced the fuel pump, fuel filter, both injectors, parts of the egr system, o2 sen and exh, distributer, plugs and wires, timing belt,. i brought it to an old mechanic, he adjusted the timing. it ran a little better after, but not close to what it should be. when i first crank it up the check eng light comes on, then it goes of after one min. any sugestions???

What code? Ur truck has TBI, so heading is wrong. But, how many miles? 94 suburban? 234k miles? Age brings issues. Worn rings, valves and so on. So, truck is running rich? Fouled plugs? Terrible mileage? What exactly is wrong?

it is 94 silverado/1500/pick up. it has 285,000 miles. it does not burn oil much, about 1/2 qt every 2 months. it gets terrible mileage, the exhaust smoke is a light gray color, so it is getting too much gas. the check eng lite does not stay on long enough for me to get a code. when i start the truck the lite comes on, when i start to drive, about 5 mins, the lite goes out. i have not checked the plugs yet.

Light grey = burning oil, black = too much gas, typically. I’d have a compression test done, it might just be worn out, or have valve problems.