The 7.3L Powerstroke engine uses a HEUI (Hydraulically Actuated Electronically Controlled Unit Injector) fuel injection system. This means that the fuel injectors are actually fired by highly pressurized engine oil, not directly by fuel pressure. This high-pressure oil is supplied by the High Pressure Oil Pump (HPOP) to two separate oil galleries, one in each cylinder head (one in the driver's side, one in the passenger's side). If you’re savvy with the 7.3, you know this, but what many don’t know is this supply is inconsistent.

 

The problem with the factory setup:

In the stock configuration, each cylinder head's high-pressure oil gallery is independent receiving their supply directly and independently, from the HPOP. You’ve got eight injectors drawing oil at different times, tens of times per second. And they’re all drawing from one column of oil (per side). Just like the fuel “dead head” issue, this means that the injectors furthest away from the HPOP, may not be receiving the oil they need. This issue is made worse with larger aftermarket injectors, or with high performance tunes. Some of the issues this causes are:

Pressure Drops/Spikes: The furthest injectors (at the end of the rails) or injectors under heavy load may experience pressure drops, spikes or general inconsistencies, especially at idle or during rapid acceleration.

"Cackle" or Rough Idle: Inconsistent high-pressure oil can cause the injectors to fire unevenly, leading to the characteristic "7.3L cackle" or a rough idle.

Reduced Performance: If the injectors aren't receiving optimal and consistent oil pressure, they can't fire as efficiently or deliver the full amount of fuel they're capable of, impacting horsepower and torque.

Injector Damage: The injectors use oil for lubrication too. But they also use it as a cushion. There are many fast moving parts within the 7.3 injector that rely on the oil to slow them down. Think of a syringe, it takes a lot more force to push the plunger down when there is fluid in it than when it’s empty. Over speeding these parts, plus the lack of lubrication, causes damage.

 

The Fix?

We tie the oil galleries together at the back of the heads with a High Pressure Crossover Kit (aka, an HPX kit). By creating a direct link between the two galleries, the high-pressure oil can more easily flow and equalize pressure across both sides of the engine. Preventing one side from starving while the other has excess pressure. Pressure spikes and drops are reduced. The engine runs smoother with less injector cackle and improved throttle response. Enhanced injector life is also a huge benefit.

In essence, an HPX kit acts like a balance pipe for your high-pressure oil system, making sure every injector gets its fair share of highly pressurized oil, resulting in a happier, healthier, and often more powerful 7.3L Powerstroke.

We should note, many will say that this upgrade is not necessary. It's definatley not one of those mandatory fixes (for most at least). You're truck isn't likely going to die early without it. But we've shared the facts, and it does make a difference, one we've seen hundreds of times. How much of a difference it makes varies between trucks based on age and how worn the fuel systems are. 

Check Them Out:

Stainless Steel HPX - Ford 7.3L Powerstroke (94-97): https://www.riffraffdiesel.com/stainless-steel-hpx-94-97/

Stainless Steel HPX - Ford 7.3L Powerstroke (99-03): https://www.riffraffdiesel.com/stainless-steel-hpx-99-03/