Thread: Want to increase performance/efficiency Newly rebuilt 91 chevy 350 TBI

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Sounds like a great project - couple things come to mind.

The Melling cam would be fine if you had converted from EFI to a carbureted engine; however, it may be a problem as it will give the ECM fits. A stock GM cam would have been a better choice. You already know the Engine Control Module (ECM) is responsible for making a lot of decisions based on engine temperature and ambient conditions. As a minimum, typical signals it needs to perform are:

1. CTS (Coolant Temperature Sensor) It's typically in the thermostat housing and it needs to be plugged in.

2. Oxygen Sensor - for headers the sensor should be in the collector, just behind the header flange. You may need to get a three wire (heated) sensor to keep the sensor warm. The sensor itself is a one wire plug to the stock harness.

4. Manifold Absolute Pressure sensor (MAP) - typically mounted on a plate somewhere on the intake manifold.

5. Manifold Air Temperature (MAT) sensor in intake manifold

6. Some ECMs have an input for an Incoming Air Temperature sensor (IAT) in the air cleaner or near the MAT that needs to be hooked up. This is often overlooked in conversions and discarded with the air intake plumbing. If your ECM is looking for this signal and not finding it, there will be timing and fuel delivery issues.

7. ESC = Electronic Spark Control - This sends the signal from the knock sensor(s) to the ECM to reduce the timing if it hears a knock

8. Fuel pump – the stock one in the Jeep probably is not sufficient for your TBI engine. Carter 5000 is an inline designed for this type of swap. it flows 45GPH at 75 PSI.

As to reprogramming the ECM - probably not cost effective. There are many aftermarket chip available for less than $100 - check this site:

CHEVROLET SILVERADO 1500 GF Peformance Chip

I'm sure many more will chime in with additional suggestions.

Again, Welcome to CHR
Glenn

Thx Glenn for the warm welcome!! The engine runs great, plenty of HP and great excel. but I know it can be better!! Like I said, this engine is complete, with all sensors connected with original wiring harness, now you did make me think of an idea!! It has the jack to connect a diagnostic computer to, so maybe I should check it and see if there are any codes and make sure of no failures. I'll check that tomorrow....