If we were to oversimplify how power is made, we’d say this: As more pressure is created in the cylinders, more torque is delivered to the wheels. That pressure can be a result of increased boost pressure, fuel, a combination of both, or the resulting combustion event. As simple as that may be, it still holds true that as power increases, so does cylinder pressure. Knowing this, you’ve likely already upgraded from factory head bolts to studs and may have even fire-ringed the heads. However, a lesser-known evil lies in the fact that the fuel injectors can actually become dislodged from the head under extreme circumstances.
Two options exist for preventing this failure: billet hold-down clamps, and screw-in injector cups. By far the most effective is the latter, and the folks at Industrial Injection have cornered the market. Performing this installation isn’t for the faint of heart, because if done improperly the cost is a wrecked head. It also goes without saying that the task needs to be performed with the heads removed from the engine, so it’s wise to do the job when the engine is already apart, as ours was. It is also highly recommended that a machine shop do the tapping, as the threads need to be as perfect as possible. That said, you could either call us brave or stupid, because we set out to see if it is possible to perform the task by hand. Armed with a decent mechanical knowledge and a good deal of patience, we installed Industrial’s screw-in injector cups in our rebuilt Freedom Racing Engines heads. We had no observable issues with the installation, but only time will truly tell, so be sure to check back as we load up the miles. Follow along with the installation below, but be warned: What you’re about to see isn’t for the squeamish!
| Despite being offered as a kit with the injector cups and tap cutting fluid, Industrial Injection’s screw-in injector cups are not intended to be a do-it-yourself project. However, if you find yourself mechanically inclined enough and willing to take the risk, it is certainly not an impossible task to perform at home. In addition to the kit, you’ll also need a tap handle, thread locking compound, brake cleaner, and injector cup O-rings.
| Seen here is one of Industrial Injection’s screw-in cups next to a well-used factory cup. You’ll notice the main difference is the threaded section on the tip of the cup. Industrial’s cups are custom made with this in mind; they are not simply threaded factory cups.
| Industrian Injection Duramax Screw In Injector Cups New
| We started our project with a set of freshly rebuilt heads from Freedom Racing Engines. If you’re planning to install these in used heads, a thorough cleaning is in order before beginning. The focus of our work is here, where the injector cup meets the combustion chamber.
| Included with the kit is a bottle of Tap Magic cutting fluid. This oil is specifically formulated for tapping aluminum. The tap needs to be kept well lubricated during the entire process, as it will ensure a clean and easy cut.
| The included tap has a pilot that fits snuggly into the injector cup bore. This is the most critical part of the operation, as the tap must start threading perfectly straight. If the new threads are cut at an angle, the injector cups may not seat properly in the head.
| It’s important to go slow and keep the tap properly lubricated during the cutting process. If at any point it gets difficult to turn the tap, stop and add more lube. It’s also important not to reverse the tap. When the threads are cut, simply release the tap and remove it from the opposite side of the head.
| After cutting the threads, the area needs to be cleaned of oil and debris. Brake cleaner does a fantastic job of blasting away all the unwanted crud. You’ll also need to flip the head over and clean all the aluminum shavings out of it in much the same manner.
| What you’re left with is perfectly cut threads ready to accept the new injector cups. The downside, if there is one, is that this head will now only accept screw-in injector cups; there is no going back.
| Much like standard injector cups, Industrial’s screw-in units require a copious amount of thread locking compound to be applied to the newly threaded area as well as the lower mating surface of the cup. In this regard, there’s no such thing as too much, so go ahead and lay it on thick.
| Before inserting the cups, thread locker should be applied to the threads on the head. We found a simple cotton swab to be the easiest manner of application.
| Next, the O-rings are installed on the injector cups. These need to be oiled along with the bore into which the cups will be inserted in order to ensure a smooth entry and no damage to the seals. Industrial doesn’t provide O-rings with the kit, but they can be purchased separately and are inexpensive. Don’t try and reuse old O-rings.
| Once everything is in order, the cups can be gently lowered into the heads from the topside.
| A special adapter is included with the kit to tighten the new cups. Industrial recommends torquing the cups to 35 ft-lb after they bottom out. Take care during this step, as the tool for tightening the cups is delicate, and the tiny pins can be easily damaged if the tool comes out of alignment.
| When all is said and done, the process takes only a couple of hours from start to finish—as long as the heads are already removed from the engine. If installed correctly, these new injector cups will last a lifetime and should never need to be removed. However, if for some reason they do need to come out, they can be unthreaded the same way they went in and reused indefinitely.