Camshaft Bearing


Removing Camshaft Bearings

  • Remove and label cam bearings.
  • Cam bearings are inexpensive and are usually replaced.
  • Remove the cam bearings with a cam bearing tool.
  • A special washer must be used with the driver, or the tool's mandrel pieces may be ruined.
  • Washers of two different sizes are provided with the tool.
  • Use the largest washer possible.
  • Too small a washer can result in broken segments.
  • Line up the segments with the spaces in the mandrel.
  • The rear cam plug can be knocked out with the cam bearing tool.
  • Label the bearings with a felt marker, or put them in labeled baggies.
  • They may need to be referred to when determining block positions of the new bearings.

Installing Camshaft Bearings

Cam bearings are normally press fit into the block or head using acam bearing tool and a ball peen hammer. it is easy to damage the camshaft bearings while installing them. be sure they are properly aligned before attempting to drive them into place.

Sometimes cam journals are different sizes. The smallest is at the rear of the block. New bearings can be checked for approximate fit by putting them on cam bearing journals before installation.

When the bearings are installed, they should require moderate force to drive them into the bores.If a bearing can be installed too easily, it may be the wrong bearing for the bore or an oversized bearing may be required.If the bearing is too tight, it may be in the wrong bore or it may be the wrong bearing for the engine.

Following is a typical procedure for installing camshaft bearings:

  • Lay the bearings out in order on the workbench.
  • If different sized bearings are used, the larger bearing is usually installed at the front of the engine block, then progressively smaller bearings are installed toward the rear of the block.
  • Make sure the bearing bores are clean.
  • Use an emery cloth to clean the cam bearing bores.
Bearings should not be sanded with emery cloth because pieces of emery grit can become embedded in the bearing surface.
  • Select the cam bearing tool.
  • Then select a mandrel closest to the cam bearing size.
  • Start the installation of the bearings beginning with the rear bearing. Do not use any lubricants on the outer diameter of the bearing unless directed to do so by the service manual.
  • Place the bearing on the mandrel (it will fit loosely), and turn the bearing driver clockwise until the mandrel is snug in the bearing.
  • Lubricate the bearing with light engine oil.
  • Start the bearing into the block by tightening the tool as much as possible by hand.
  • Make sure the oil hole in the bearing aligns with the oil hole in the block before driving the bearing into the block housing.
  • Give the tool one sharp rap with a large hammer, and then loosen the mandrel approximately 1/8" turn before continuing.
  • Be sure to re-check this adjustment occasionally when driving the bearing into place because the tool will sometimes loosen and damage the bearing.
  • Refer to the engine manufacturer's specifications for proper bearing positioning.
  • Generally, the bearing will be seated correctly when the mandrel is flush with the face of the block.
  • Some cam bearings must be installed further in the bore to align with the oil holes in the block.
  • Hold the guide cone tightly against the front of the block.
  • Hold the cam bearing driver snugly against the bearing during installation so it does not bounce, or the end of the bearing can be damaged.
  • Drive the bearing into the block by using sharp blows with a heavy ball peen hammer.
  • Remove the mandrel by withdrawing the cam bearing tool. Check for any nicks or burrs on the bearing and remove, if present. Repeat for all bearings.

Some overhead camshafts do not have bearing inserts. The bores in the aluminum casting serve as a bearing surface.

The use of a standard bushing driver (cam bearing tool) and hammer is not recommended because aluminum bearing supports are very easily damaged or broken. This can result in expensive head replacement.If the bores are damaged, some aftermarket manufacturers supply insert bearing replacements. To install the replacement bearings, the bores should be smoothed and made bigger to fit the new bearing. A machine shop can do this for you.

The cam bearings in a pushrod engine are installed before the crankshaft is installed. This makes it easier to align the oil holes in the bearings to the corresponding holes in the block. The timing sprockets and chain are lubricated by oil from the front cam bearing. Many front bearings are pounded in past the block surface.

This leaves an oil passage in front of the bearing that provides lubrication to the cam timing sprocket and chain.

Other bearings have a notch cut into them. The bearing is installed with the notch facing the cam gear.

Positioning the Oil Hole

After the cam bearings have been installed, the oil hole in the bearings should be checked for proper alignment with those in the block or head. This will ensure correct lubrication and oil supply in vital engine areas. Follow the manufacturer's recommendations when positioning the oil hole.

When there is an oil groove around the total cam bore in the block, positioning the oil hole toward the top also allows oil to enter the bearing easily. It will be carried under the cam as it rotates.

Oil is carried under the cam as it rotates. Courtesy of Federal-Mogul Corporation.

The following recommendation from Federal-Mogul Corporation can be followed:

  • Install the bearings with their oil holes at approximately the 2 o'clock to 4 o'clock position, viewed from the front, so that oil hole alignment can be observed easily.
  • Avoid positioning the oil hole between the 5 o'clock and 8 o'clock positions.

Proper alignment can be checked by inserting a wire through the holes or by squirting oil into the holes.

Checking oil hole alignment. Courtesy of General Motors Corporation, Service Technology Group.

If the oil does not run out, the holes are misaligned. This procedure should be repeated with each bearing.

Some engines, such as the small block Chevrolet V-8, have a rear cam bearing bore that is wider than the bearing. Failure to align the bearing oil hole to the block oil groove can result in a total loss of oil pressure in this engine.

Checking Bearing Fit

After installing the bearing, install the cam and turn it. If it does not turn easily, remove it and look for any high spots that can be scraped with a bearing scraper. High spots on the bearing will become polished as the cam is rotated after it is first installed.

  • A special flex hone is available for honing small amounts off of cam bearings.
  • If necessary, Scotch Brite™ can be used to polish cam bearing surfaces.