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Project EFI GT
Mustangs Plus gives you the lowdown on installing Electronic Fuel Injection in an Early Mustang
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If you have read any of our past Newsletters, you know that Mustangs Plus has been working on Project EFI. Project EFI is the installation of an early 1990's Electronic Fuel Injection set up on a stock 1966 Mustang GT Coupe with the original 289 engine and 4-speed transmission. The reason we chose to do this project is because we receive many calls each week from customers wanting information on installing newer engines, which are equipped with EFI, into their early Mustangs. So, being the "hands on" type, we decided that in order to give our customers the best possible information, we should do our own conversion and then we would have the correct answers. So, with the help and expertise of Ron Morris Jr., we started and concluded the project. It was a great success which taught us a lot.

One of the biggest concerns that we hear about EFI is the cost. In all cases until now, to get EFI you also had to change the engine and transmission. So we chose to add EFI to an already running car with the 289 engine and factory 4-speed transmission. This, we reasoned, would take a lot of the cost away from doing the conversion and interest many people who already had a good running Mustang but wanted to have an EFI Classic Mustang.

Adding EFI to an early engine brought two concerns to light, but neither turned into problems. The first was that the water passages on the EFI intake manifold and the original heads were of different sizes. We went ahead and installed the intake on the stock 289 engine and have run it for several hundred miles with no problems. Still, if you do this conversion, you'll want to keep this in mind.

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Our 1966 GT Coupe as it looked before and after! Once the EFI was installed, you could only tell by looking under the hood! Our 1966 GT Coupe as it looked before and after! Once the EFI was installed, you could only tell by looking under the hood!

Before our EFI installation. The engine compartment is pretty much bone stock except for engine color and detailing.Before our EFI installation. The engine compartment is pretty much bone stock except for engine color and detailing.
This is the EFI unit as we bought it at the local swap meet for a paltry $25.00! Such a deal!This is the EFI unit as we bought it at the local swap meet for a paltry $25.00! Such a deal!
This is where we cut the hole for the wire harness to pass through the firewall. The computer sits under the cowl. The glove box is untouched. This is where we cut the hole for the wire harness to pass through the firewall. The computer sits under the cowl. The glove box is untouched.
A trial fit. Notice that the stock valve covers will not work because of the oil filler tube. We replaced them with new ones. A trial fit. Notice that the stock valve covers will not work because of the oil filler tube. We replaced them with new ones.

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