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Installing a Camshaft into a Cummins 6BT Engine

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The video above shows Diesel Pro Power, Inc. customer Imperial Diesel Service installing a camshaft for a Cummins 6BT during a full engine rebuild. This guide provides a comprehensive, step-by-step process for installing a camshaft into a Cummins 6BT engine, covering preparation, removal of the old camshaft, inspection, installation of the new camshaft, alignment, and final checks.

This article is optimized for mechanics, rebuilders, and Cummins 6BT engine owners looking to either replace a worn camshaft or install a new one during a full overhaul. While the steps below are highly detailed, for exact torque specifications and specialized measurements, always refer to the OEM service manual or verified torque charts for the Cummins 6BT.

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See Our Cummins 6BT Parts Catalog

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Understanding the Camshaft in the Cummins 6BT Engine

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The Cummins 6BT camshaft plays a critical role in the timing and operation of the engine. It opens and closes the intake and exhaust valves in precise synchronization with the pistons’ movement. In the 6BT, which is a pushrod-style diesel engine, the camshaft is located in the engine block and operates the valves through tappets, pushrods, and rocker arms.

When worn or damaged, the camshaft can cause performance issues such as:

• Loss of power

• Poor fuel efficiency

• Increased exhaust smoke

• Hard starting

• Abnormal valve noise

Replacing the camshaft is often part of a full rebuild or when significant wear is detected during maintenance.

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Preparation for Camshaft Installation – Cummins 6BT Engine

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Before installing a new camshaft, preparation is crucial. A clean, organized, and well-lit workspace helps prevent mistakes and ensures engine longevity.

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Tools and Equipment Needed

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• Engine stand or secure workbench

• Standard and metric socket sets

• Torque wrench (capable of low and high torque ranges)

• Camshaft installation tool or handle

• Plastigauge for bearing clearance checks

• Feeler gauges

• Engine assembly lube

• Clean lint-free rags

• Oil drain pan

• Magnet-on-a-stick (to retrieve small parts if dropped)

• Cummins 6BT-compatible camshaft

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Replacement Parts Commonly Installed with the Camshaft

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• New camshaft bearings (if required)

• New tappets (recommended when installing a new camshaft)

• New thrust plate and bolts

• Gaskets for front timing cover

• Assembly hardware if corroded or stretched

Safety Precautions

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• Wear gloves when handling engine components to avoid cuts from sharp machined edges.

• Use safety glasses to protect eyes from debris.

• Keep all flammable materials away from the work area.

• Make sure the engine is securely mounted before turning the crankshaft or installing components.

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Removing the Old Camshaft – Cummins 6BT

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If the engine is in the vehicle, removing the camshaft requires major disassembly. For most rebuilds, the engine is out and mounted to a stand.

Step 1 – Drain the Engine Oil

• Remove the oil drain plug and drain all oil into a suitable container.

• Dispose of oil according to local regulations.

Step 2 – Remove the Valve Cover and Rocker Arms

• Unbolt the valve cover and set it aside.

• Loosen rocker arm adjusting screws.

• Remove rocker arm assemblies, keeping them organized for reinstallation or replacement.

Step 3 – Remove Pushrods and Tappets

• Carefully lift each pushrod, marking them to ensure they return to their original location if being reused.

• Remove the tappets from their bores. This may require a magnetic retrieval tool or tappet removal tool.

Step 4 – Remove the Timing Gear Cover

• Remove all bolts securing the front timing gear cover.

• Pry the cover gently to avoid damage to the mating surfaces.

Step 5 – Remove the Camshaft Gear

• Rotate the crankshaft to align timing marks on the crank gear and cam gear.

• Remove the camshaft gear retaining bolts.

• Use a gear puller if necessary to remove the gear without damage.

Step 6 – Remove the Thrust Plate

• Unbolt and remove the camshaft thrust plate, noting orientation for reassembly.

Step 7 – Remove the Camshaft

• Using a camshaft handle or an assistant, carefully slide the camshaft out of the block, supporting its weight to avoid scoring the bearing surfaces.

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Inspecting Components Before Installation – Cummins 6BT Engine

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Camshaft Bearings

• Inspect for scoring, pitting, or uneven wear.

• Replace if there is any sign of damage.

Tappets

• Always inspect tappet faces for pitting, wear, or concave surfaces.

• Replace as a set with a new camshaft.

Camshaft Journal and Lobe Inspection

• Ensure no burrs or sharp edges are present.

• Check all lobes for proper profile and absence of wear patterns.

Gear Train and Timing Marks

• Confirm timing gears are in good condition. Replace if teeth are worn or chipped.

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Installing the New Camshaft – Cummins 6BT 

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Step 1 – Lubricate Bearings and Lobes

• Coat all camshaft journals and lobes with high-quality assembly lube.

• Apply a thin layer to the camshaft bearings inside the block.

Step 2 – Install the Camshaft

• Carefully slide the camshaft into the block, supporting its weight as you pass each journal through its bearing.

• Rotate slightly as you insert to avoid catching lobes on bearings.

Step 3 – Install the Thrust Plate

• Apply thread locker to bolts.

• Torque bolts to OEM specifications.

• Ensure the thrust plate is installed in the correct orientation.

Step 4 – Install the Camshaft Gear

• Align timing marks with the crankshaft gear.

• Install bolts with thread locker and torque to specification.

Step 5 – Reinstall Tappets and Pushrods

• Lubricate tappet faces with assembly lube.

• Insert tappets into their original bores.

• Reinstall pushrods in their marked positions.

Step 6 – Reinstall Rocker Arms and Adjust Valves

• Install rocker arms and torque hold-down bolts.

• Adjust valve lash according to OEM specifications.

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Setting Camshaft Timing – Cummins 6BT 

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The 6BT uses gear-driven timing, making it more durable than chain systems but still requiring precision alignment.

• Rotate crankshaft so that #1 piston is at top dead center (TDC) on compression stroke.

• Align timing marks on crankshaft and camshaft gears.

• Double-check all timing marks before securing bolts.

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Final Steps and Initial Startup – Cummins 6BT 

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Step 1 – Reinstall Timing Gear Cover

• Clean mating surfaces.

• Install a new gasket or sealant.

• Torque bolts evenly.

Step 2 – Prime the Oil System

• Fill crankcase with fresh oil.

• Use a priming tool to circulate oil before starting.

Step 3 – Rotate the Engine by Hand

• Turn crankshaft through at least two complete revolutions.

• Confirm no interference or binding occurs.

Step 4 – Initial Startup

• Start engine and let it idle while monitoring oil pressure.

• Listen for abnormal noises.

• Check for leaks around front cover and seals.

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Troubleshooting After Camshaft Installation – Cummins 6BT 

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Low Oil Pressure

• Verify oil pump operation.

• Check for correct bearing clearance.

Abnormal Noise

• Recheck valve lash.

• Inspect pushrods and rocker arms.

Poor Performance

• Confirm camshaft timing alignment.

• Ensure injectors are functioning correctly.

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Maintenance After Installation – Cummins 6BT 

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• Recheck valve lash after initial break-in period.

• Monitor oil and coolant levels.

• Keep a maintenance log for future reference.

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FAQ – Installing a Camshaft in a Cummins 6BT

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Q: Should I replace tappets with a new camshaft?
A: Yes, it is strongly recommended to replace tappets when installing a new camshaft to ensure proper wear patterns.

Q: Can I reuse my old camshaft gear?
A: Only if it is in perfect condition with no chipped or worn teeth.

Q: How do I check camshaft bearing clearance?
A: Use Plastigauge between journal and bearing, then measure against OEM specification.

Q: Is assembly lube necessary?
A: Yes, it prevents dry start damage to lobes and bearings during initial engine start-up.

Q: How long should I run the engine during break-in?
A: Typically 20–30 minutes at varied RPM, but follow specific guidelines for the camshaft manufacturer.