REMOVAL & INSTALLATION
See Figure 1
- Disconnect the negative, then the positive battery cable. Remove the battery cover and battery from the vehicle.
- Remove the timing chain front cover.
- Remove the timing chain and camshaft sprocket.
- Remove the rocker arm/shaft assemblies.
- Remove the lifters, and label or position them for assembly in their original locations.
- Drive the camshaft plug inward, then remove it from the cylinder head with a magnet.
- Carefully pull the camshaft from the rear of the cylinder head through the oversized camshaft plug hole. Turn the camshaft back and forth slowly while withdrawing to help prevent journal or bearing damage.
- Clean and inspect all parts prior to installation. Lubricate the camshaft and carefully insert it through the hole at the rear of the cylinder head.
- Coat a new rear cylinder head plug with Loctite® 242 or equivalent and install it using a standard bushing driver.
- Install the valve lifters into their original bores, or if the camshaft has been replaced, install new lifters.
- Install the rocker arm/shaft assemblies.
- Install the timing chain and camshaft sprocket.
- Install the timing chain front cover.
- Install the battery and tighten the battery hold-down nut and screw to 80 inch lbs. (9 Nm). Connect the positive battery cable only, at this time.
- Connect thepositive, then the negative battery cable, start the engine and check for leaks.
See Figures 2, 3, 4 and 5
Be very careful when working around the camshaft sprockets and timing chain cover during this procedure. If a bolt or washer is accidentally dropped between the front cover and engine assembly, the cover will have to be removed for retrieval.
- Disconnect the negative battery cable and remove the serpentine drive belt.
- Disconnect the spark plug wires from the plugs, remove the EGR valve solenoid attachment screw and remove the PCV fresh air hose.
- Remove the camshaft cover, then inspect the cover's silicone insulators for cracks or deterioration, and replace as necessary.
- Turn the crankshaft clockwise until the mark on the crankshaft pulley is in alignment with the pointer on the front cover and the No. 1 cylinder is at Top Dead Center (TDC) of the compression stroke. Both camshaft dowel pins will be at the 12 o'clock position and the timing pin holes will be aligned when the No. 1 cylinder is at TDC. If necessary, the right wheel and splash shield can be removed to help observe the timing marks.
- Carefully remove each camshaft sprocket' retaining bolt. Use a 7 / 8 in. (21mm) open end wrench to hold the camshaft from turning while removing the bolts.
- For 1992-98 vehicles, position a front angled support fixture in front of the camshaft sprockets.
- Attach the camshaft sprocket adapters to the end of each camshaft using the pilot bolts, but do not tighten the bolts. For 1992-98 vehicles, the front angled support should come between the sprocket adapters and camshaft sprockets.
- Remove the upper timing chain guide and both front camshaft bearing caps.
- For 1991 vehicles, position the front angled support fixture.
- Secure the support fixture using 7 / 8 in. bolts/blocks and align the 2 holes in each camshaft sprocket, adapter and the front support fixture. Install the 4 nuts, but do not tighten. The steel blocks should be installed against the rearward side of the camshaft sprocket. Tighten the sprocket pilot bolts to 19 ft. lbs. (25 Nm) while holding the camshafts from turning with an open end wrench.
- Move each camshaft sprocket off the end of the camshaft by rocking the sprocket forward or by carefully prying between the end of the camshaft and the sprocket. Then tighten the 4 nuts and bolts with blocks from the side of the support fixture to 19 ft. lbs. (25 Nm).
- Install the 2 bolts retaining the support fixture to the engine front cover and tighten the bolts to 89 inch lbs. (10 Nm). Then remove each camshaft sprocket pilot bolt while holding the camshafts with a wrench.
- Carefully pry between the sprocket and the end of the camshaft to move the camshaft rearward. Pry only enough to remove its end from inside the sprocket pilot otherwise camshaft or lifter damage may occur.
- Uniformly loosen and remove the remaining camshaft bearing cap bolts. To prevent bolt/cap damage, do not use power tools and make several passes. Then remove each camshaft. Position the bearing caps for installation in their original locations.
- Clean and inspect all parts prior to installation. Oil the camshaft and install with the IN camshaft on the intake side and EX camshaft on the exhaust side.
The dowel pin in each camshaft must be located at the 12 o'clock position during installation to prevent valve and piston damage.
- Install all bearing caps, except for the forward pair, in their original positions, making sure the arrows on the caps are pointing forward toward the camshaft sprockets. Lightly oil each of the cap bolts, then install and uniformly tighten the bolts to 124 inch lbs. (14 Nm).
- Install one camshaft sprocket pilot bolt in each camshaft and tighten to 124 inch lbs. (14 Nm) in order to pull the camshaft fully forward and align the sprocket support for installation of the sprocket onto the camshaft.
- Remove the 4 sprocket support bolt/blocks and nuts. Then, for 1991 vehicles only, remove the front angled support fixture. The torque axis mount system of the 1992-98 vehicles requires the fixture to remain in place longer.
- Verify that the camshafts are fully positioned forward and install the 2 forward bearing caps and the upper chain guide. The caps are marked E1 or I1 for exhaust or intake and must be positioned with their arrows pointing towards the sprockets. Tighten the cap bolts to 124 inch lbs. (14 Nm).
- Make sure the camshaft dowel pin aligns with the slot in each camshaft sprocket. If necessary, rotate the camshaft slightly (1-2 degrees) and move each sprocket from the adapter onto the end of the camshaft. Fully seat each sprocket on the end of each camshaft.
- Remove the 2 sprocket pilot bolts and adapters while using a wrench on the camshaft flats to assure the camshaft cannot move.
- For 1992-98 vehicles, remove the support angled fixture.
- Install the camshaft sprocket retaining bolts and washers. Hold the camshafts and tighten the bolts to 76 ft. lbs. (103 Nm).
- Verify all visible timing marks and holes are in alignment. Turn the crankshaft clockwise until the mark on the crankshaft pulley aligns with the mark on the front cover. Check timing by inserting 3 / 16 in. drill bits through the camshaft sprocket alignment holes, into the cylinder head. If the alignment pins cannot be inserted, turn the crankshaft 360 degrees clockwise and repeat. If the pins cannot be inserted within 1-2 degrees of either TDC position, the camshafts are not properly timed. Do not start the engine until the camshafts are timed.
- Apply a small drop of RTV across the cylinder head and front cover T-joints. Inspect the old camshaft cover gasket and replace if damaged. Install the gasket and the camshaft cover. Tighten the fasteners in proper sequence to 89 inch lbs. (10 Nm).
- Install the right splash shield and wheel, if removed to observe the timing marks.
- Install the PCV and fresh air hoses, the EGR valve solenoid attaching screw and the spark plug wires.
- Install the serpentine drive belt and connect the negative battery cable.
- Start the engine and check for leaks.
See Figures 6, 7, 8 and 9
- Clean the camshaft in solvent and allow it to dry.
- Inspect the camshaft for obvious signs of wear: scores, nicks or pits on the journals or lobes. Light scuffs or nicks can be removed with an oil stone.
- Position the camshaft in V-blocks with the front and rear journals riding on the blocks. Check if the camshaft is bent using a dial indicator on the center bearing journal. The run-out limit at the center journal is 0.004 in. (0.1mm) for DOHC engines or 0.0028 in. (0.07mm) for SOHC engines. Replace the camshaft if run-out is excessive.
- Using a micrometer, measure the camshaft lobes across their maximum and minimum lobe height dimensions. Subtract the lobe width from the lobe height to arrive at lobe rise. Replace a SOHC camshaft if any lobes have a rise of less than 0.252 in. (6.4mm). Replace a DOHC camshaft if any intake rise is less than 0.351 in. (8.91mm), or any exhaust rise is less than 0.339 in. (8.61mm).
- Using a micrometer, measure the diameter of the journals and replace any camshaft containing a journal that is less than the minimum. For SOHC engines, journal diameter should be greater than 1.747 in. (44.375mm). DOHC engines should have a minimum camshaft journal diameter of 1.139 in. (28.925mm).
- Measure the diameter of the camshaft bearings. For the DOHC engine, temporarily install the bearing caps to the cylinder head in order to take the measurement. Bore diameter must be less than 1.753 in. (44.513mm) for SOHC engines or 1.144 in. (29.05mm) for DOHC engines, or the cylinder head must be replaced.
- Subtract the journal diameter measurements from their respective bore diameter measurements to calculate oil clearance. Replace the camshaft and/or cylinder head if clearance is more than 0.0054 in. (0.138mm) for SOHC engines or 0.005 in. (0.125mm) for DOHC engines.
- Position a precision straightedge across the bottom of the cylinder head camshaft contact surfaces. Use a feeler gauge to inspect for warpage; replace a cylinder head with warpage of more than 0.0025 in. (0.064mm) for SOHC engines or 0.003 in. (0.075mm) for DOHC engines.