Valve clearance (3.5L and 3.7L engines) — check and adjustment
Note: The engine must be cold before checking the valve clearances.
Note: Checking and, if necessary, adjusting the valve clearance is only necessary after replacement of the camshaft (s) or other valve-related parts, or if the valve train is making excessive noise.
Note: 2.7L engines are equipped with hydraulic lifters and there is no valve adjustment needed.
1. Disconnect the cable from the negative terminal of the battery (see Engine electrical systems).
2. Remove the spark plugs (see Tune-up and routine maintenance).
3. Remove the valve covers (see Valve covers — removal and installation).
4. Using a socket and a breaker bar on the crankshaft pulley center bolt, rotate the engine until the cam lobes on the cylinder to be checked are pointing away from the lifters.
5. Measure the clearance of the valves with a feeler gauge (see illustration). Record each measurement and compare your measurements with the desired valve clearance found in this Chapter’s Specifications. Note which ones are out of specification, as this data will be used later to determine the required replacement lifters.
3.5 Measure the valve clearance for each valve with a feeler gauge of the specified thickness — if the clearance is correct, you should be able to feel a slight drag on the gauge as you pull it out
6. Repeat Steps 4 and 5 until the clearances for all valves have been measured.
7. If a clearance is out of specification, the lifter must be replaced with a new lifter that has a different thickness head to correct the clearance. Refer to Section Camshafts and tappets/roller followers and lash adjusters — removal, inspection and installation and remove the camshafts to access the lifters.
8. Mark the lifters that are to be replaced, and record which valve they came from. Use a micrometer to measure the thickness of the head of the lifter, making sure the measurement is precise and on the center projection on the underside of the lifter (see illustration).
3.8 Use a micrometer to measure the thickness of the head of the lifter
9. To calculate the correct thickness for a replacement lifter that will place the valve clearance within the specified value, use the following formula:
N = R + (M1 — M2)
N = thickness of new lifter
R = thickness of old lifter
M1 = measured valve clearance
M2 = standard valve
10. Lifters are marked on the underside as to their size. A marking of 3.310 on the underside of the lifter indicates a thickness value of 3.31 mm, or 0.13 inch.
11. Mark the new lifters as to their destination, lubricate them with engine assembly lube and install them. After replacing the lifters, reinstall the camshafts and the timing chains (see Sections Timing chains and sprockets — removal and installation and Camshafts and tappets/roller followers and lash adjusters — removal, inspection and installation), then re-check the valve clearances.