A CCV delete removes the crankcase ventilation system from your 6.7 Cummins engine

A CCV delete (closed crankcase ventilation delete) is a modification that removes or bypasses the factory crankcase ventilation system on a 6.7 Cummins diesel engine. Instead of routing crankcase gases back into the intake manifold through the factory system, a CCV delete vents those gases directly to the atmosphere or into a catch can that you empty manually.

The factory system on 6.7 Cummins engines recirculates crankcase vapors — a mix of unburned fuel, oil mist, and combustion byproducts — back into the engine's intake. This reduces emissions but can cause oil buildup in the intake, carbon deposits on valves, and moisture accumulation inside the engine over time. A CCV delete is intended to prevent those problems by eliminating the recirculation loop entirely.

Key Takeaways

  • A CCV delete removes the factory system that routes crankcase gases back into the intake manifold, instead venting them to atmosphere or a catch can.
  • The modification can reduce oil and carbon buildup in the intake and valves, but it increases crankcase pressure and may void your engine warranty.
  • A catch can setup requires regular maintenance — you must drain accumulated oil and fluid every few hundred miles to prevent overpressurization.
  • CCV deletes are not street-legal in most states because they increase emissions and bypass emissions control equipment.
  • The modification is most common on high-mileage engines or those running heavy tuning, where factory system problems become more pronounced.

How the factory CCV system works and why people modify it

The 6.7 Cummins factory CCV system pulls crankcase vapors through a separator (which removes oil mist) and routes the remaining gases back into the intake manifold. This design meets emissions standards by preventing those vapors from entering the atmosphere. However, the separator does not catch all the oil, and over time oil residue accumulates in the intake, on the intake valves, and throughout the intake tract.

On high-mileage engines or those running aggressive tuning, this buildup becomes severe enough to affect performance, fuel economy, and valve cleanliness. Some owners also report that moisture trapped in the recirculation loop can promote rust inside the engine or contribute to coolant contamination. A CCV delete is intended to eliminate these problems by stopping the recirculation entirely.

What changes when you delete the CCV system

Removing the CCV system stops oil and moisture from being pulled back into the intake. This means your intake manifold, intake valves, and combustion chambers stay cleaner over time, and you avoid the oil sludge buildup that occurs with the factory system. Owners often report cleaner valve deposits and less carbon formation after a CCV delete, especially on engines with high mileage or heavy use.

However, a CCV delete also increases crankcase pressure. Without a path for those gases to escape into the intake, pressure builds inside the engine block. This higher pressure can stress engine seals, gaskets, and bearing surfaces over time. It can also push oil past seals and gaskets, leading to external leaks. The longer you run without addressing the pressure, the greater the risk of seal failure.

Catch can setups and maintenance requirements

Most CCV delete installations use a catch can — a small tank that collects oil and fluid vapors before they vent to atmosphere. The catch can sits between the crankcase vent line and open air, trapping oil mist and condensation so they do not escape as emissions or coat your engine bay.

A catch can requires regular maintenance. As it collects oil and fluid, internal pressure builds. You must drain the catch can every 500 to 1,000 miles (the interval depends on how hard you drive and how much blow-by your engine produces). If you do not drain it regularly, pressure inside the can rises, which defeats the purpose of venting crankcase pressure and can force oil past seals elsewhere in the engine. Some owners also install a second catch can on the PCV line for additional separation.

Catch cans come in different sizes and designs. Larger cans hold more fluid and require less frequent draining, but they take up more engine bay space. Smaller cans are easier to fit but need more frequent attention. You will also need to decide whether to vent the catch can to atmosphere or to a secondary container, and whether to run a single can or dual cans on both crankcase lines.

Legal and warranty implications

A CCV delete is not street-legal in most U.S. states. The modification increases emissions by venting crankcase gases to atmosphere instead of routing them through the factory emissions control system. Federal emissions regulations prohibit removing or disabling emissions equipment, and most states enforce this rule during vehicle inspections. If your vehicle is registered for street use, a CCV delete can result in a failed inspection or a citation.

A CCV delete will also void your engine warranty. Diesel engine manufacturers consider any modification to the crankcase ventilation system a breach of warranty terms. If you experience engine problems after a CCV delete, the manufacturer will not cover repairs, even if the problem is unrelated to the modification. This is a significant financial risk on a new or relatively new engine.

When a CCV delete makes sense and when it does not

A CCV delete is most practical on high-mileage engines where the factory system has already caused visible problems — heavy oil buildup in the intake, carbon on the valves, or a history of intake leaks. It is also more common on engines running aggressive tuning or frequent towing, where crankcase blow-by is higher and the factory system struggles to keep up.

A CCV delete is less practical on newer engines still under warranty, or on engines used primarily for street driving where emissions compliance matters. The maintenance burden of a catch can — draining it every 500 to 1,000 miles — is also a real cost in time and attention. If you do not want to maintain a catch can regularly, a CCV delete is not a good fit.

Some owners choose a middle path: cleaning the factory CCV system thoroughly, replacing the separator, or upgrading to an aftermarket separator designed to trap more oil. These approaches keep the factory system intact, maintain emissions compliance, and preserve your warranty while reducing (though not eliminating) the oil buildup problem.

Installation and component choices

A basic CCV delete involves disconnecting the factory CCV lines from the intake manifold and routing them instead to a catch can or directly to atmosphere. The work is straightforward on most 6.7 Cummins engines — you remove the factory separator, disconnect the hoses, and install new lines and a catch can. Many owners do this work themselves with basic hand tools, though some prefer to have a diesel shop handle it.

Component choices affect how well the system works. A larger catch can with internal baffles separates oil and fluid more effectively than a small can with no internal structure. A catch can with a drain valve at the bottom is easier to empty than one you have to tip or disassemble. Some owners also add a secondary catch can on the PCV line, or install a pressure relief valve to prevent excessive crankcase pressure if they forget to drain the main can.

Frequently Asked Questions

Will a CCV delete damage my engine?

A CCV delete itself does not damage the engine, but neglecting catch can maintenance does. If you do not drain the catch can regularly, crankcase pressure builds and can force oil past seals and gaskets, leading to leaks and potential seal failure. If you maintain the catch can properly, the main risk is long-term wear on seals from sustained higher crankcase pressure.

Can I run a CCV delete without a catch can?

You can, but it is not recommended. Venting crankcase gases directly to atmosphere increases emissions significantly and is illegal for street vehicles. It also means all the oil mist and moisture that the factory system would have separated now enters the air. A catch can is the standard way to manage crankcase pressure while keeping most of the oil out of the atmosphere.

How often do I need to drain a catch can?

Most catch cans need draining every 500 to 1,000 miles, depending on engine condition and driving style. High-mileage engines with more blow-by may need draining every 300 to 500 miles. The only way to know your engine's rate is to install the can, check it after 500 miles, and adjust your schedule based on how much fluid accumulated.

Will a CCV delete affect my fuel economy or power?

A CCV delete itself does not change fuel economy or power. However, by keeping the intake cleaner, some owners report slightly better fuel economy over time compared to an engine running a factory CCV system that has accumulated heavy oil deposits. The effect is usually small and depends on how dirty the factory system had become.

Can I reverse a CCV delete if I want to?

Yes. Reversing a CCV delete means reconnecting the factory CCV lines to the intake manifold and reinstalling the factory separator. The work is straightforward and takes a few hours. However, if the factory separator has been removed or damaged, you will need to source a replacement part, which can be expensive.