When I lived in California, I purchased a baby blue 1968 Ford F-100 Custom for $1,000 from a local tow yard. The truck showed its age, but the body was straight, and there was minimal rust. All it needed to run (albeit poorly) was a fuel pump and an air filter.
The truck came with its original 360ci V8 and T-18 manual transmission. We suspected that the original motor had something between 200,000 and 400,000 miles on it. The engine was tired, and no amount of bolt-on modification could change that.
I eventually decided to swap in a 300 straight six for reliability and (slightly) improved fuel economy. Now you must be thinking, “why on earth would you swap a V8 for a straight six?” And yes, it seems absurd but I was dead-set on making it work.
This was my first engine swap. My buddies called it ‘The Great Engine Downgrade of 2014’ with good reason. Nonetheless, it was plenty of fun. Eventually, it did work—and it was pretty easy. Here’s how to swap a Ford 360 for a 300 inline-six.
I drove to Richmond, California, to pick up the $400 donor motor. This 300 came out of a 1976 F-100 stepside. I took it home with the original three-speed manual transmission still attached. I took apart the engine for inspection and cleaning. It turns out that it’d been rebuilt and bored .90 over—which was unusual. It was in excellent condition and had likely been rebuilt recently. I put it back together and removed the old 360 from the truck.
I bought an Offenhauser 4-barrel intake and a Holley 600. Many on the forums recommend a 350 CFM carb, which may have worked better. I also chose to stick with ignition points. Points worked with the existing wiring, and the distributor was dirt cheap. A set of Summit Racing-brand headers came next for a total cost of less than $1,000.
Removing the 360 FE
All I needed to remove the 360 was a set of ¾” sockets, a ratchet, a hacksaw, and a cherry picker. I removed the shifter from the T18 and unbolted the U-joint and transmission mount. Next, I cleaned off all the wires, cables, and hoses attached to the engine. A Sawzall made quick work of the exhaust. Then I removed the engine mounts and started lifting. It took some effort to find the correct angle, but eventually, everything was out on the ground. Check out our article on pulling a junkyard motor for more specifics.
Unlike GM, Ford bell housings weren’t widely standardized across the line in 1968. The FE motors had a different bell housing than the Windsor V8s and 300 six engines. Thankfully, the truck was a manual, and I had two manual transmissions in the garage. I simply unbolted the bell housing from the ‘76 three-speed and swapped it onto the T18. The transmission bolted right on.
The 300 shared the same engine perches as the FE motors, but in a different location. Due to the length of the 300, the perches had to be moved forward about an inch. Luckily, the cross member already had holes drilled for factory straight-six trucks. So I aligned the perches with the other holes and it was ready to go.
The only junkyard part I needed was a gas pedal—the original 360 gas pedal connected to a bar with a convoluted mechanical linkage system that sucked. The 300 required a shorter bar with a receptacle for a cable. I was lucky enough to find a donor truck at the junkyard, so I got my pedal and went to work rigging up a cable system for the new 4-barrel.
Installing the 300
The trickiest part of the swap was installing the new motor. I was fairly convinced that the long 300 wouldn’t fit with the transmission attached, but we made it work. A bit of hammer-clearance was required on the headers, but everything eventually lined up fine.
I hooked up the fuel lines, wires, hoses, and finally, the battery. With a bit of gas dumped down the carb, it fired right up. I drove it to the local exhaust shop that same day.
Exhaust and Final Touches
The truck sounded ridiculous with open headers. The neighbors complained within 10 minutes. I bought two Cherry Bomb glass packs and piped them out on each side. It sounded like a tractor under load, and I absolutely loved it.
Swapping a 360 FE for a 300 I6 was a great learning experience. It was easy, and we finished in less than a week working afternoons in a suburban garage. I sold the truck shortly after, and the 360 became a stroker motor for a local shop truck.