Thread: 87 454 TBI eng

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What are the advantages of changing from TBI to carbuerator if any?

Originally Posted by leorilla

What are the advantages of changing from TBI to carbuerator if any?

Assuming you're talking the OEM unit, the TBI gives you ECU controlled air/fuel ratio across the load range, adjusting automatically for variations in barometric pressure whether due to altitude changes or just weather, inlet air temperature, and probably uses a knock sensor. Your Lambda settings will maximize cruise efficiency for best attainable mileage. If you change to a carburetor you'll select jets to optimize your WOT airflow at your highest power point (multiple runs, pulling plugs to gauge the air/fuel ratio by electrode color), and once you have it jetted in for max power start working on finding the best metering rods, springs and accelerator pump settings to yield the best cruise efficiency you can get, along with the best throttle response. Once you have it dialed in it will be good for normal barometric pressure changes for that area, but will be off if you normally go from sea level to the mountains, and your efficiency will vary from the deep cold of winter to the heat of summer. In short, you're taking a step backwards if you ditch the EFI system, IMO. Others may well disagree.

Reduced fuel economy, poorer performance, you'll need to modify the fuel system, but you won't have to maintain the sensors

When I got the truck the timing was way off. I set it correctly.this eng was a transplant from ? It is an 87 454 TBI. It has an inline blue holley fuel pump, Hooker headers,3" exhaust all the way back with flomasters. 1 o2 sensor in the driver side, I think the map sensor is working. I changed the plugs and it runs better but does load up one in a while at lower speeds. It has plenty of power. I did not build the truck but trying to get it to be smooth. plugs are gapped at 40,they are Autolights. Thanks for the advise.

Leorilla.
66elky@gmail.com

Check the TBI incoming fuel pressure......they required somewhere between a carb and a normal injection 40 psi......dont remember what the exact pressure requirement is.

Originally Posted by robot

Check the TBI incoming fuel pressure......they required somewhere between a carb and a normal injection 40 psi......dont remember what the exact pressure requirement is.

Good point, Robot. The GM TBI likes 9-13psig at the engine, which is a lot lower than direct port injectors need to see.

Also, to set the timing, you have to disconnect some wire......forgot which one.