Old School meets electronic controls

March 1, 2010 | By Richard Prince


I bought a 1990 L98 Corvette engine that I would like to install in my 1957 Chevrolet 150 two-door. I have all of the brackets for the motor and I also have the power steering pump, alternator, water pump, serpentine belts and pulleys, etc. I also have the complete wiring harness and computer from the firewall forward.

However, I am not familiar with the modern engine electronics—I’m old school and an old man! I have been told that I do not need all of the electronics (MAP, MAF, TPS, etc.) that came with the engine to make it run in my car. I also have been told that I should buy an aftermarket wiring harness and computer to run the motor properly and that I also need to install an electric fuel pump with return fuel lines back to the gas tank. I have the stock 1957 gas tank and I had it tinned inside and out. Can I modify my existing gas tank to run the L98 engine? The L98 engine has the HEI distributor and uses spark plugs.

Also, I would like to install a 700R4 transmission. Will a 700R4 bolt up to the 1990 L98 engine?


You do not have to use the OEM computer, wire harness, and full array of sensors when you install the L98 in your ’57 Chevy. You will definitely not need a mass air flow sensor if your engine is, in fact, from model year 1990 because the 199092 GM TPI engines used a MAP (manifold absolute pressure)-triggered Speed Density system rather than a MAF system.

You say that you have “the complete wiring harness and computer from the firewall forward” but don’t mention whether you have the L98 donor car’s dash harness.

The Assembly Line Diagnostic Link (ALDL) is usually not incorporated into the OEM engine harness, but is instead in the instrument panel harness. And the engine harness has a whole array of wires and connectors that you likely won’t use, including those that mate with the electronic transmission, EGR, air conditioning high pressure switch, vehicle speed sensor and VATS module.

As an admitted old school guy with no electronic engine control experience you are probably better off simplifying the installation with a new, matched computer and wire harness. There are various outfits that sell these. Howell Engine Development, Inc. (howellefi.com) is a reliable source with a knowledgeable staff. The injection system in the L98 engine requires a high-pressure fuel pump and return line to the gas tank. Typical OEM applications used a high-pressure electric fuel pump mounted inside the gas tank. You can use an external fuel pump that will work just as well.

The pump should deliver a minimum of 50 psi pressure and 24 GPH volume. The fuel supply line should be at least 3/8-inch and the return line going back to the fuel tank should be a minimum of 5/16-inch.

A 700R4 overdrive automatic transmission will bolt right up to your L98 engine and is a good choice.