REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15Gasoline Engines
- Disconnect the negative battery cable.
- Drain the coolant and save it if still fresh.
- Remove the air cleaner.
- Remove the air conditioning compressor, but do not disconnect any A/C lines. Secure the compressor to one side.
- Disconnect the AIR hose at the check valve. Remove the turbocharger assembly, if so equipped.
- Remove the intake manifold.
- When removing the right cylinder head, loosen the alternator belt, disconnect the wiring and remove the alternator.
- When removing the left cylinder head, remove the dipstick, power steering pump and air pump if so equipped.
- Label the spark plug wires and disconnect them.
- Disconnect the exhaust manifold from the head being removed.
- Remove the valve cover. Scribe the rocker arms with an identifying mark for reassembly; it is important that the rocker assembly is reinstalled in the same position as it was removed. Remove the rocker arm bolts, rocker arms and pivots.
- Take a piece of heavy cardboard and cut 16 or 12 holes (depending on whether the engine is a V6 or a V8 or 8 or 6 holes if you are only removing one head) in it the same diameter as the pushrod stems. Number the holes in relation to the pushrods being removed. This cardboard holder will keep the pushrods in order (and hopefully out of harm's way) while they are out of the engine. Remove the pushrods.
Pushrods MUST be returned to their original locations.
- On models equipped with power brakes, it is necessary to disconnect the brake booster and turn it sideways to remove the No. 7 pushrod.
- Remove the cylinder head bolts, and remove the cylinder head and gasket. If the head seems stuck to the block, gently tap around the edge of the head with a rubber mallet until the joint breaks.
- NEW head gasket(s) should always be used. Match the old gasket with the new one to make sure they are exactly the same. Gaskets on the 260 V8 must be installed with the stripe facing up: 307 V8 gaskets do not have a stripe. If the gasket has a bead, install it so the bead is upward. If there are dowel pins, locate the holes in the gasket over them. On the 285 and 301 engines, coat all rocker stud lower threads, the cylinder head bolt threads, and the underside of the bolt head with thread sealer. On 1986-87 3.8L V6 engines, coat the bolt threads with a heavy body thread sealer. On all engines, the head bolts should be dipped in clean oil before installing. Except on the 1986-87 3.8L V6 and 1988-90 5.0L V8, tighten all head bolts in sequence and in small stages to the specified torque.
On the 1986-87 3.8L V6:
- First follow the sequence, torquing the bolts to 25 ft. lbs. (34 Nm).
- Watching the torque reading, turn the bolts, in the same sequence, 90 degrees tighter. If the torque reading reaches 60 ft. lbs. (81 Nm), stop turning that bolt and proceed to the next one.
- Repeat the step above, turning the bolts another 90 degrees in sequence, but, again, stopping if a bolt reaches 60 ft. lbs. (81 Nm).
On the 1988-90 5.0L V8:
- First follow the sequence, torquing the bolts to 40 ft. lbs. (54 Nm).
After torquing, turn the bolts, in the same sequence, the specified number of degrees.
Bolts 1 through 7 and 9 - 120 degrees
When installing the intake manifold remember to use new gaskets and new O-ring seals, if the manifold has them. Pushrods MUST be returned to their original locations.
- Install the pushrods into their original location as removed.
- Install the rocker arm assemblies into their original location. It is important that the rocker assembly is reinstalled in the same position as it was removed. Torque the bolts to specifications. Also, refer to the Rocker Arm section in this section.
- Install the valve cover with a new gasket.
- Connect the exhaust manifold to the head that was removed.
- Reconnect the spark plug wires.
- When installing the left cylinder head, install the dipstick, power steering pump and air pump if so equipped.
- When installing the right cylinder head, install the alternator, connect the wiring and tighten the belt.
- Install the intake manifold using a new gasket.
- Connect the AIR hose at the check valve. Install the turbocharger assembly, if so equipped.
- Install the air conditioning compressor if so equipped.
- Install the air cleaner.
- Refill the radiator with coolant.
- Connect the negative battery cable.
- Disconnect the negative battery cable. Remove the intake manifold, using the procedure outlined in the Intake Manifold section in this section.
- Remove the rocker arm cover(s), after removing any accessory brackets which interfere with cover removal.
- Disconnect and label the glow plug wiring.
- If the right cylinder head is being removed, remove the ground strap from the head.
- Remove the rocker arm bolts, the bridged pivots, the rocker arms, and the pushrods, keeping all the parts in order so that they can be returned to their original positions. It is a good practice to number or mark the parts to avoid interchanging them.
- Remove the fuel return lines from the nozzles.
- Remove the exhaust manifold(s), using the procedure outlined above.
- Remove the engine block drain plug on the side of the engine from which the cylinder head is being removed.
- Remove the head bolts. Remove the cylinder head.
- Clean the mating surfaces thoroughly with a gasket scraper and solvent. Install new head gaskets on the engine block. Make sure the new gasket matches the old gasket exactly. DO NOT coat the gaskets with any sealer. The gaskets have a special coating that eliminates the need for sealer. The use of sealer will interfere with this coating and cause leaks.
- Install the cylinder head onto the block.
- Clean the head bolts thoroughly. Dip the bolts in clean engine oil and install into the cylinder block until the heads of the bolts lightly contact the cylinder head.
- Torque the bolts, in the sequence illustrated, to 100 ft. lbs. (136 Nm). When all bolts have been tightened to this figure, begin the torquing sequence again, and torque all bolts to 130 ft. lbs. (176 Nm).
- Install the engine block drain plugs, the exhaust manifolds, the fuel return lines, the glow plug wiring, and the ground strap for the right cylinder head.
- Valve lifter draining: Install the valve train assembly. You'll have to remove, disassemble, and drain oil from all eight lifters associated with the removal of one cylinder head or, if both heads have been removed, all 16 lifters. Remove the valve lifter guide retaining bolts, and then remove the lifter guide. Then, remove each lifter from its bore, keeping it in order for replacement in the same bore. This is especially important since some lifters are 0.010 in. (0.254mm) oversize (these bores are marked with an oval). To disassemble each lifter, remove the retainer ring with a small prybar. Then, remove the pushrod seat and oil metering valve. Remove the plunger and plunger spring (the plunger, valve disc, spring, and check retainer may remain fully assembled). Now, turn the lifter upside down and drain the oil from the lifter body completely.
Don't wipe any of the parts dry, however, as there must be some lubrication at startup. Then, reassemble each lifter by first installing the plunger spring over the check retainer. Hold the plunger upside down so that the spring will not cock and insert it into the lifter bore. Then, install the oil metering valve and pushrod seat into the bore and install the retaining ring.
Install the lifters (in original bores) and the lifter guide and retaining bolts. Install the pushrods in their original positions with the wing at the top. Install the rockers and pivots and bolts, torquing the bolts alternately to 28 ft. lbs. (37 Nm).
- Install the intake manifold. Refer to the procedure in the Intake Manifold procedure in this section.
- Install the valve covers. These are sealed with Room Temperature Vulcanizing (RTV) silicone sealer instead of a gasket. Use GM #1052434 or an equivalent. Install the cover to the head within 10 minutes, while the sealer is still wet.
CLEANING & INSPECTION
See Figures 16, 17 and 18
Any diesel cylinder head work should be handled by a reputable machine shop familiar with diesel engines. Disassembly, valve lapping, and assembly can be completed by following the gasoline engine procedures.
Once the cylinder head has been removed, it can be inspected, cleaned and machined (if necessary). Set the head(s) on a clean work space, so the combustion chambers are facing up. Begin cleaning the chambers and ports with a hardwood chisel or other non-metallic tool (to avoid nicking or gouging the chamber, ports and especially the valve seats). Chip away the major carbon deposits, then remove the remainder of carbon with a wire brush fitted to an electric drill.
Be sure that the carbon is actually removed, rather than just burnished.
After decarbonizing is completed, remove the valve train and take the head(s) to a machine shop and have the head hot tanked (cast iron only). In this process, the head is lowered into a hot chemical bath that very effectively cleans all grease, corrosion, and scale from all internal and external head surfaces. Also have the machinist check the valve seats and re-cut them if necessary. When you bring the clean head(s) home, place them on a clean surface. Completely clean the entire valve train with solvent.
See Figures 19, 20 and 21
Lay the head down with the combustion chambers facing up. Place a straightedge across the gasket surface of the head, both diagonally and straight across the center. Using a flat feeler gauge, determine the clearance at the center of the straightedge. If warpage exceeds 0.003 in. (0.076mm) in a 6 in. (152mm) span, or 0.006 in. (0.152mm) over the total length, the cylinder head must be resurfaced (which is similar to planing a piece of wood). Resurfacing can be performed at most machine shops.
When resurfacing the cylinder head(s) of V6 or V8 engines, the intake manifold mounting position is altered, and must be corrected by machining a proportionate amount from the intake manifold flange.