Basic Camshaft Installation Techniques

When replacing a camshaft that has failed permanently, take the time to diagnose and correct the problem before installing a new camshaft, lifters and/or followers.

Once you've disassembled the engine and removed the old components, thoroughly clean the exposed portions of the engine. Excessive debris may not completely drain with the oil and could become lodged on other components in the engine– causing additional problems after the engine is reassembled. Finally, check all oil passages to make sure they are free of dirt and foreign particles. Remember, these components operate in tolerances as little as one millionth of an inch – just a speck of dirt could mean the difference between a job well done and a job you'll have to do again.

Inspect lifter bores for excessive wear. This usually shows up as an oblong or egg-shaped wear pattern. It is generally a good idea to check your valve springs for proper length, pressure, and to make sure they are square. Inspect the cam bearings for wear and signs of fatigue. Be especially concerned if you are replacing a camshaft that failed prematurely. The cause of the camshaft failure may have had an effect on the cam bearings. If you find the cam bearings need replacement or if you have an Overhead Cam (OHC) engine that does not use cam bearings, check the housing bores for proper size and alignment. Install new Clevite® cam bearings when required.

Lack of lubrication is one of the most common causes of camshaft failure during the initial start-up. If the camshaft and other valve train components are not properly pre-lubricated, they can be damaged within the first few camshaft revolutions. Once the damage has occurred, no amount of lubrication will prevent the impending failure of these parts. Use a high quality break-in lube such as Clevite Camshaft Cam Guard™ (part# CL400) as you reassemble the engine. Cam Guard has an extreme pressure (EP) lubricant rating and excellent adhesion quality. It will help prevent scuffing and galling during the initial start-up caused by the high loads placed on valve train components. The adhesion quality also will prevent the lubricant from draining off the components during engine reassembly. Cam Guard is functionally equivalent to all OEM pre-lubricants. It is strongly recommended that motor oil NOT be used as a prelube. Motor oil has a tendency to drain off from coated components. The light oil film that remains is insufficient to protect the camshaft or other components during the initial break-in period. Clevite Cam Guard can also be used during engine reassembly on lifters, followers, push rods, rocker arm shafts, valves, valve guides, bearings and timing components.

Thoroughly coat the camshaft lobes, bearing journals and distributor drive gear with Cam Guard®. Carefully slide the new camshaft into the engine block or head, taking precautions not to damage the cam bearing surfaces. When the new camshaft is installed, check that it turns freely in the engine. NOTE: On Overhead Cam (OHC) engines with split cam towers, make sure that the cam bearing caps are installed in the correct position and direction. If they are not, it could cause the camshaft bore to be distorted and seize the camshaft when the caps are torqued down.

Because of the function and design relationship between the camshaft lobe and the lifter, it is extremely important that new lifters be used with a new camshaft. While to the naked eye cam lobes and lifter faces may appear flat, on all but a few applications they are not. Cam lobes generally have a taper from .0007" to .001" across the face to cause lifter rotation. Lifter faces are commonly ground to a domed shape with an approximate .002" crown. The offset, along with the taper of the cam lobe, causes the lifter to rotate as the cam turns. Before installing the lifters in the lifter bores, generously coat the lifter bores with Cam Guard®. Coat the lifters and/or followers one at a time as they are installed. After they have been installed, rotate the camshaft to check for binding or mis-alignment.

Recheck all parts and gasket mating surfaces. Next, reassemble the engine to the proper OEM specifications using MAHLE® gaskets.

Mechanical Lifters
Set valve lash using OEM procedures and the proper specification for your camshaft.

Hydraulic Lifters
Although hydraulic lifters require no adjustment during normal service, it is important to check the lifter pre-load when lifters are installed. Adjust as necessary. Lifter pre-load is the distance between the retaining snap ring and the push rod seat in the lifter when the lifter is on the heel of the cam lobe with the valve closed. A number of things can affect lifter pre-load:

• Resurfacing the heads and/or block deck
• Changes in camshaft diameter
• Changes in push rod length
• Changes in valve length
• Changes in rocker arm length or geometry
• Changes in head gasket thickness
• Changes in lifter height
• Valve job
• Different rocker arm stands or shafts

When installing new hydraulic lifters, follow the proper OEM procedures for checking and adjusting lifter pre-load.

Some OEMs require the use of special oil additives for camshaft break-in. Although this is not necessary with the proper use of Cam Guard, they can be added if desired. Other oil additives should not be added until after break-in is complete.

It is important that the engine starts as quickly as possible. Prolonged cranking may damage the camshaft, lifters and/or followers. Before starting the engine, top off the coolant level and make sure the ignition timing is properly set. After starting the engine, DO NOT let it idle. It is essential to run the engine at 1500-2000 RPM for at least 20 minutes. Because the camshaft and lifters are primarily lubricated by a splash-effect of oil from the crankshaft, any RPM below 1,500 may result in insufficient lubrication and will not rotate the engine fast enough to force the lifters to rotate on the camshaft. The rotation allows the lifters to properly seat against the camshaft during this critical break-in procedure. During the first 20 minutes, carefully monitor oil pressure. If any problems arise, shut down the engine immediately. Remember, DO NOT allow the engine to idle. Finally, repeat start-up procedures beginning with priming the oiling system after the problem has been corrected.