Compass 4WD L4-2.4L VIN W (2007)
Camshaft: Description and Operation
Camshaft - Description
CAMSHAFTS
Both camshafts have five bearing journal surfaces and two cam lobes per cylinder. The two front journals are larger to allow for feeding oil to the
variable valve timing (VVT) camshaft phasers. Flanges on the third smaller journal control camshaft end play. At the rear of each camshaft is an integral
cam sensor target.
CAMSHAFT BEARING CAPS
The front cam bearing cap spans both camshafts, and includes dowels for precise alignment. The front exhaust journal has a select fit bearing insert. This
bearing is required to seal the oil passage to the camshaft phaser, because a portion of the lower bearing saddle is machined away for head bolt access.
The select fit is required to minimize bearing clearance and oil leakage. An exhaust bearing grade (1,2 or 3) is stamped into the front bearing cap
adjacent to the exhaust cam journal. The bearings are also marked with the corresponding grade markings. If the bearing is replaced, the same grade
must be used. Due to unique purpose of this bearing, it may appear to have uneven wear patterns. Unless the wear is excessive it is no cause for concern.
The front intake journal has a full lower bearing saddle, and therefore, no bearing insert is required.
All small bearing caps have a formed in arrow to assist in assembly. All small bearing cap arrows must point towards the center of the cylinder head. The
small bearing caps are marked for position during the manufacturing process, and must be reinstalled in their original position.
The #1 small cap includes a passage to direct oil from the cylinder head oil gallery to the #1 small bearing journal, and into the camshaft as well. The
hollow camshaft then distributes oil to the remainder of the small journals. Oil flowing out of each cam journal lubricates the valve tappets.
The #3 small cap is machined at the front and rear face to control camshaft end-play. This cap has dowels for precise alignment.
