Fire Rings, Studs, Valve Springs, Push Rods and Injectors
The 7.3L Power Stroke is as an extremely reliable engine, some say the most reliable diesel that Ford ever placed in a pickup. However, it was never known for being fast, still isn’t, but they can be built to make pretty decent power—heck—right now, the current horsepower record is a healthy 1,226 hp held by Matt Maier and his OBS Ford.
For this 7.3L, we weren’t looking to go that big (well at least not yet). The original plan was for 500 hp, but after talking with Dave Armstrong from Swamps Diesel, he made us realize that now-a-day’s making 500 hp or more with a 7.3L is relatively simple and that if we ever wanted to go bigger that we should take the steps towards that larger hp goal now as opposed to later. In years past, injector technology, but more importantly, tuning technology, wasn’t at a level like it is today. It used to be that big injectors were smoky, inconsistent beasts that didn’t have good street manners.
Now that the platform has been around for over two decades, Swamps has the technology to make a massive 300/200 injector work extremely well on or off the street at just about any power level, with just the change of a tune; and be relatively smoke free at the same time. So instead of going with an injector capable of a maximum 500 hp (roughly a 238/80 model) we decided on the set Dave from Swamps suggested, 300/200 injectors easily capable of providing enough fuel for 750 hp.
Since the new Swamps injectors would be raising cylinder pressures significantly, we knew we’d have to be doing some head work to contain the added pressure. Head studs from ARP Bolts were on the list for sure, and Dave assured us that the 7.3L with a set of studs securing the heads to the block would handle 45 psi of boost all day long. But again, since we planned on going bigger in the near future, he recommended a set of his heads that had been machined to accept a fire ring.
What’s a fire ring you ask? Well, normal heads seal to the block using just a gasket; a fire ring is a steel ring that sits in a groove machined in the head. It’s then clamped between the head and block taking the place of that gasket around the cylinder. With these steel fire rings in place, Dave tells us we’ll never have to worry about blowing a head gasket (now a fire ring) until we move up to the largest set of injectors made for 7.3Ls, (400/400s) with a very healthy amount of nitrous on top of that. And at that point, the stock forged rods would have long since failed anyway. So we’re much more than set with the fire ring’d heads.
But keeping the pressure in the heads doesn’t end with the fire rings, as the stock valve springs are only capable of holding back roughly 35 psi of boost. Beyond that pressure, the risk of “valve float” is very real. Floating a valve means that at high boost levels the valve can actually get pushed open by the boost pressure. The valve can then end up contacting the piston at top dead center leading to catastrophic engine failure. Since the 300/200 injectors are more than capable of helping the right turbo produce 60 psi we decided to replace the valve springs with some beefier ones. For the springs we went to Irate Diesel and picked Owner and 7.3L expert Jake Enos’ brain for information.
As per their recommendations, yet again we didn’t settle for the ones designed for the power we were going for. Nope. We stepped up to their stage with two springs capable of holding more boost than they’ve ever seen a 7.3L produce. Because of the extra force it would take to open the valves with the new springs, Jake also recommended we install a set of their titanium push rods as the stock ones would surely bend under the pressure. On top of that, Jake pointed out that the stock intake runners wouldn’t last long. Being made from thin stamped steel, they simply bend under higher boost pressure causing a boost leak. So Jake recommended a set of his fabricated aluminum intake runners made from quarter inch aluminum.
The install took us a couple days to complete at our local shop, Bud’s Diesel. To supply the injectors with a healthy amount of fuel, we also installed a fuel system from Irate Diesel. The article on that kit can be found just a few pages past this one, it starts on page XX. Check back next issue where we’ll be tuning the truck and adding some much needed traction bars. 600 hp…here we come! DW
Inside the 7.3L Injector
The 7.3L uses high-pressure oil to create fuel injection pressure. That high pressure oil when commanded to by the computer, pushes down on the Intensifier Piston (A) that then pushes down on the Plunger (B) which then forces fuel through the nozzle to create the combustion event. Fuel pressure supply to the injector is around 70 psi and oil pressure can be anywhere from XXXX psi all the way up to 4,000 psi. Due to the size difference between the Intensifier Piston and the Plunger, it results in a multiplication of pressure reaching upwards of 23,000 psi of fuel entering the cylinder. Inside the head are two galleries that feed the injectors: (C) for fuel and (D) for oil.
7.3L Injector Sizes
What do they tell us?
300/200 is simply the amount of fuel the injector body will flow, over the percentage the nozzle has been honed out over stock. So we’ve got a set of injectors that flow 300 cc’s of fuel, with a nozzle that’s 200-percent larger than stock. Generally speaking, the closer to stock the nozzle size is, the more efficiently it will atomize fuel (like holding your thumb over the end of a garden hose,) but it will also be restricted in the amount of fuel it can flow. Injector body size will dictate how much fuel is available to the nozzle. To put it in perspective, a stock injector flows around XXXcc’s of fuel. So these 300/200’s flow XX% more fuel than stock. Pairing the right size nozzle with the correct injector body flow rating is very important when deciding how you want your truck to run.
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