7.3L Ford F-250 Super Duty Power Stroke

Admit it. There are times when you wish you had a little more power. Whether you tow with your diesel, race it, or use it as a daily driver, we bet you've had some crazy idea like wishing you could just flip a switch and get an instant boost in power. Well, propane injection might be what you're looking for.STC Performance offers a propane kit that can give you an instant 60-80hp increase and slightly better fuel economy. We went to STC while its mechanics were putting a propane kit on a 7.3L Ford Power Stroke to better understand how a propane kit works and how it's installed. The truck had already been upgraded with a ball-bearing turbo, an exhaust, an intake, and a mild programmer. The owner wanted more power-a kind he could turn on and off-so he decided to go with a propane kit for when he needed that extra boost in performance.

To start off the install, the AFE intake was removed from the truck to allow access to where the regulator would be mounted.

This stock plastic intake support (where the AFE filter clamps on) was drilled out to accept the injection fitting.

The regulator was modified for a fixed amount of propane flow; it can be set at 60 hp, 80 hp, or even more. STC recommends an 80hp increase as the safe limit if a programmer or other mods are being used in conjunction with the propane system.

A custom mount that's included in the propane kit was then bolted to the stock intake piece. This is used to mount the regulator in a convenient location right next to the intake stream.

The propane injection fitting was then mounted in place. This should give you an idea of how the propane is injected into the intake stream.

Driving Impressions
To demonstrate the potential of propane, the guys at STC took us for a ride around the block in their propane-equipped shop truck. There's actually a noticeable increase in acceleration once the system is activated, and it also seems to make for a smoother-accelerating vehicle. If you've ever ridden in a truck with nitrous, this propane system feels like a mild nitrous kit, only you don't spend $5 every time you use it-plus, you can use it on the street. Under part throttle, we toggled the arming switch on and off, and you could feel the truck immediately surge forward once the propane was activated. There was no lag in the system, and a 60-80hp increase felt like a conservative claim.