Project 500 HP 7.3L

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.

Going Big

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.

After spending roughly an hour getting the cab off the frame, the guys at Bud’s immediately tore off the valve covers and started breaking down the heads.

This would be the last these factory push rods would see the 7.3L, as they’d soon be replaced with titanium ones from Irate Diesel.

After the rockers, glow plugs and push rods were pulled, the injectors came out next. Since they’re filled with oil, it’s a good idea to let them drain before placing them on the bench as seen here.

The head has an oil gallery that feeds the injectors. Once the injectors are pulled, it will drain into the injector bores. Again, it’s a good idea to let this oil drain through the rings (or suck it out with a fluid extraction machine) before pulling the head to reduce the amount of cleanup needed once done.

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.

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Fire Rings

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.

The factory head bolts were then pulled and the heads were removed. The heads weigh around 140 lbs., removing them is a two-person job at least.

With the heads out of the way, some time was spent cleaning the deck up. It’s important to use as little powered abrasive’s here as possible, such as an air sander, since the possibility of deforming the block is a real one. Deforming it will cause sealing issues.

See the grove around the valves? That’s there to accept the fire ring, which will be the engines new way of keeping cylinder pressure where it belongs. Swamps also decked the head to make sure it was perfectly true; they performed a full valve job and also swapped out the old injector cups for new ones.

Factory valve springs will only hold about 35 lbs. of boost before they begin to “float” and kiss the piston causing catastrophic engine failure. Since we’re planning on seeing 60 psi of boost at some point, we swapped the springs out for a set of stage two valve springs from Irate that are capable of handling much more than 60 psi.

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.

Valve Float

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.

The factory intake runners are stamped steel and will leak at higher boost levels. So we swapped them out for Irate’s much more robust fabricated aluminum runners. They install with a bit of silicone, and the existing 10 factory bolts, they can also be installed while the head is still on the engine so you don’t need to go through all the hassle we did to put a set on your 7.3L.

Here’s the fire ring head gasket set from Swamps. It comes with 8 stainless steel rings, the gasket, as well as O-rings and supports for the water jackets.

Fire ringed heads have a bad rap: They tend to have issues with water jacket sealing, but Swamps has fixed this issue with o-rings and supports for them. The supports first get a light coating of LocTite, and are then hammered into the block. This steel will then support an O-ring, which will do the real sealing of the coolant passageways. We’ve got a few thousand miles on this 7.3L as well as a bunch of dyno runs and 1/8th mile passes and have not had one problem with the cooling system. And that’s exactly what we’ve heard from others running Swamps kit as well. Zero issues.

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.

With the coolant jacket supports done, the head gasket was laid on the block, the O-rings (A) were placed where they need to be and the fire rings (B) were placed around the cylinder.

And finally, the head could be dropped in place. This is a 3-man job, as we needed to be certain the fire rings were located correctly and that the O-rings weren’t pinched or pushed out of position. If not, the heads will leak badly. Two held the head up while the third located it over the dowel pins and rings.

With the head resting in place, the Buds Diesel crew secured it with a set of ARP studs. The studs are heat-treated and then the threads are rolled on providing XXXXXXXX clamping force when compared to stock. These heads aren’t going anywhere.

ARP uses 12-point nuts because they offer more surface area for a wrench or socket to grab on to, basically eliminating the possibility of rounding a nut off. A generous amount of ARP Ultra-Torque assembly lubricant was used on the threads and all over the washers. The lube is needed to ensure a correct torque reading.

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

Torquing the heads down is done in three different steps. Believe it or not, if you were to torque the head down incorrectly, the head can actually warp a bit causing a leak or failure. So the first pass done in a pattern recommended by ARP was done at 45 ft.-lbs., then 85 and lastly 125. But since we had fire rings in there, Swamps recommended 135 ft.-lbs. as the final setting. We did exactly that, and also re-torqued them one last time after the engine was started and brought up to temp, again as was recommended by Swamps. This is called a “hot re-torque.”

Swamps 300/200 Injectors came next. A light coat of oil on the O-rings helped them seat, and then they were torqued down for good.

Since they’re hollow to allow oil to flow through them, we placed the new Irate Diesel titanium push rods in a bath of fresh oil before installing them. After a few minutes, we pulled them out and installed them.

Last job under the valve cover was the reinstallation of the rocker arms.

With everything done under the valve covers, the engine was starting to look normal again. Check back next issue, where we’ll be tuning the 7.3L and doing a couple other supporting mods.

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.

Sources
Automotive Racing Products
800.826.3045
ARP-Bolts.com

Irate Diesel
503.435.9599
IrateDiesel.com

Swamps Diesel Performance
866.595.8724
SwampsDiesel.com

Bud’s Diesel
714.902.1467
BudsDiesel.com