We have a full selection of 6C, 6CT and 6CTA Cummins parts in stock. This is a popular engine in the marine industry, renowned for reliability and easy servicing. At Diesel Pro, we have the right parts to keep this engine going, at very competitive prices. We are proud to offer fast order processing, including shipping all orders within one business day. Plus, you can choose from a variety of shipping options, so you can get the part delivered within one day. Simply click above to get started, or read below for more information.

General Information and Specifications

The Cummins 6CTA8.3 has the following general specifications :
• Aspiration is Turbocharged and aftercooled
• Bore 4.49 inches, Stroke of 5.32 inches
• Compression ratio 16.5:1
• Engine weighs between 1330 (dry) and 1450 lbs (with fluids).
• Firing Order is 1-5-3-6-2-4

Cummins 6CTA8.6 Cooling System Specifications:
• Thermostats begin to open at between 178 and 182 degrees, and are fully open at 203 degrees F.
• Maximum recommended top tank temperature is 158 degrees F.
• The maximum allowable tank temperature is 212 degrees F.
• Water pressure at 2000 RPM should be between 15 to 40 PSI.
• Coolant flow, with thermostats fully open, at 2000 RPM) is 68 gallons per minute.

Air Intake and Exhaust Specifications:
• Maximum allowable intake restriction: 25 inches water.
• Maximum turbocharger outlet restriction: 40 inches water.

Oil Information:
• Total oil capacity for the Cummins 6CTA is 23.8 liters or 25.2 quarts.
• Minimum oil pressure is between 10 PSI (idle) and 30 PSI (rated speed).
• Normal oil temperature is between 219 to 241 degrees Fahrenheit.
• The total oil pan capacity for all engines is between 16 to 20 quarts.
• Oil flow is 28.2 gallons per minute at rated speed.

Electrical System Specifications:
• Minimum battery capacity (12 volt at 0 degrees F) is 1800 amperes.
• Minimum battery capacity (12 volt at 32 degrees F) is 1280 amperes.
• Minimum battery capacity (24 volt at 0 degrees F) is 900 amperes.
• Minimum battery capacity (24 volt at 32 degrees F) is 640 amperes.

Cylinder Head General Specifications and Information

The Cummins 6CTA cylinder head is a one-piece, crossflow type design.

How to know when to replaced cylinder head related parts:
• Any of the items are not the proper length or width. The specifications below contain the values that can be used as a guide.
• Cylinder head is cracked or no longer able to form a seal.
• Valve stems are bent or broken.
• The combustion surface has cracks that are over 10 mm long, or cracks of any length that extend towards the valve seats.
• Valve seats are burned or cracked.
• Valve stems show rust or pitting, or otherwise burned or cracked.
• The capscrew shows signs of damaged threads, or there is pitting or corrosion that exceeds 1 square cm.

Minimum and Maximum Values
• If you wish to test the head for leaking, the vacuum must not drop more than 1 inch Hg in 5 seconds. The valve to valve seat should be 18 inches Hg for used units, and 25 inches Hg for new units.
• Using a feeler gauge, the cylinder head flatness maximum is 0.008 inches for end-to-end values, and 0.003 inches for side-to-side values.
• To reuse a cylinder head, the minimum thickness would be 4.577 inches.
• The intake valve guide height would be between a minimum of 0.813 inches and a maximum of 0.833 inches, and the valve recess in the cylinder head should be between 0.043 and 0.064 inches. The exhaust valve guide height would be between a minimum of 0.886 inches and a maximum of 0.906 inches, and the valve recess in the cylinder head should be between 0.023 and 0.044 inches.
• The intake valve guide height should be between 0.813 inches and 0.833 inches. The exhaust guide height should be between 0.886 and 0.906 inches.
• The cap screw should not exceed 3.2 inches (short screw) or 6.4 inches (longer screw).

Lubricating Oil Specifications and General Information

This group includes the oil dipstick, pan and suction tube. The cooler and filter head are combined. The thermostat should allow full-flow through the oil cooler at 239 degrees F.

When to replace certain components:
• The oil pan has cracks, or the drain plug has damaged threads.
• The oil suction tube has cracks.
• The soldered joints of the oil cooler has corrosion or cracking. The oil cooler element can also be checked for leaks by submerging in 180 degree F water and injecting air.
• The plunger bore has scratching or nicks.
• Spring tension with valve open, 2.125 inches. Spring tension assembled height, 2.375 inches.
• The gaskets must be replaced whenever you remove them from the filter or cooler cover.
• The oil pump gears have chips or signs of wear.

Torque and Normal Values:
• Pressure regulating plunger, tighten to 59 ft•lb.
• Oil filter head, tighten to 18 ft•lb.
• Oil pump drive gear backlash has a minimum of 0.003 inches and a maximum of 0.013 inches.

Cooling System General Information and Specifications

The Cummins 6CTA cooling system includes the water pump, thermostats and fans. This engine uses a belt driven pump. It is generally recommended to replace the entire pump if you suspect any problems. Never run this engine without the thermostats in place as this greatly increases the chance of your engine overheating. Avoid bending the fan or using it to turn the crankshaft.

Signs that certain cooling system parts need to be replaced:
• There is a large amount of chemical buildup near the weep hole near the water pump seal.
• There are cracks in the water pump body, pulley or impeller.
• The shaft does not rotate freely.
• The thermostat or the thermostat housing shows cracks or corrosion.
• The water outlet connection is not flat, corroded or damaged.
• The oil seals are leaking, usually seen near the fan hub.
• The fan hub does not spin freely.

Torque, Normal Values and Specifications:
• When measured at the vent peacock, the minimum pressure should be 18 PSI with a 15 PSI pressure cap, or 10 PSI with a 7 PSI cap.
• The fan hub clearance should be no more than 0.006 inches.
• When installing a new fan hub, the installation force is 2023 lbf.

Rocker Assembly, Valve Tappets and Push Rods General Information and Specifications

The push rods and rocker arm assembly helps to control and regulate the performance of the engine, and includes the valve cover and crankcase breather. The Cummins 6CTA has six separate assemblies. Listed below are signs that a part needs to be replaced, as well as general specifications to help diagnose problems.

Here are signs that parts in this section need to be replaced:
• Cracks and excessive wear where the bore of the rocker arm, or on the contact surface for the valve stem.
• Rocker lever shafts has pits or scores.
• Valve cover is cracked.
• Breather tube is constricted at certain points, or it is cracked or damaged.
• The push rod is not straight, and will not smoothly roll on a flat surface.

Minimum and Maximum Values
• Rocker lever bore diameter should be between 0.8762 and 0.878 inches.
• Rocker lever shaft has a minimum diameter of 0.874 and 0.8752 inches.
• Valve tappet stem diameter is between 0.627 and 0.629 inches.