Installation (Lower) Chevrolet Astro I

1. Install gaskets on cylinder heads. Apply a 3/16" bead of RTV silicone sealant to front and rear lower intake manifold-to-cylinder block mounting surfaces. (Scheme 4) Extend bead 1/2" beyond cylinder block-to-cylinder head junction.
2. Install lower intake manifold onto cylinder block. Tighten bolts in sequence to specification. (Scheme 5) See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000). Install fuel injectors, fuel rails and electrical connectors removed during disassembly.
3. Install distributor, A/C compressor and cruise control servo (if equipped). Install gasket and upper intake manifold. See «INSTALLATION (UPPER)»(ref-50103-S29422923932003070800000). To complete installation, reverse removal procedure. Tighten fasteners to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000). Fill cooling system. See «COOLING SYSTEM BLEEDING»(ref-50103-S33609718192001121400000).

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Removal

1. Remove heat stove tube. Remove all attached brackets and heat shields. If necessary, remove dip stick tube. Disconnect oxygen sensor electrical connector.
2. Disconnect exhaust pipe from manifold. Remove exhaust manifold bolts and exhaust manifold.

Install manifold. Tighten retaining bolts to specification. See TORQUE SPECIFICATIONS . Bend lock tabs (if equipped). To complete installation, reverse removal procedure.

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(ref-50103-S19297080802001011600000) . Remove intake manifold. See «INTAKE MANIFOLD»(ref-50103-S36211046342001011600000) .
2. Remove exhaust manifold. See «EXHAUST MANIFOLD»(ref-50103-S05967259642001011600000) . Remove valve covers. Loosen rocker arm nuts. Rotate rocker arms aside. Remove push rods and mark for reassembly to original locations. Remove cylinder head bolts. Remove cylinder head.

1. Clean gasket surfaces, bolt threads and bolt holes. If using steel head gasket, thinly coat both sides of gasket with sealant. DO NOT apply sealant to composition (steel/asbestos) head gaskets. Position head gasket on cylinder block. Ensure all holes align. Coat head bolt threads with GM Sealant (1052080).
2. Install cylinder head with bolts finger-tight. Tighten head bolts in sequence to specification. (Scheme 6) Refer to the «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000). Lubricate valve tip, rocker arm pivot and push rod socket with Molykote.
3. To complete installation, reverse removal procedure. Adjust valves. See «VALVE CLEARANCE ADJUSTMENT»(ref-50103-S18029696022001011600000) under ADJUSTMENTS.

Scheme 6

Remove fan shroud. Remove fan and accessory drive belt. Remove crankshaft balancer bolt. Remove crankshaft pulley bolts and crankshaft pulley. Using Damper Puller/Installer (J-39046), remove crankshaft balancer. Pry seal from cover.

1. Coat seal lips with clean engine oil. Using Seal Installer (J-35468), install NEW seal in front cover with seal lip facing engine. Apply RTV sealant to Woodruff keyway in crankshaft balancer.
2. Using Damper Puller/Installer (J-39046), install crankshaft balancer. Install crankshaft pulley. Install crankshaft balancer bolt and crankshaft pulley bolts and tighten to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000) . To install remaining components, reverse removal procedure.

1. Disconnect negative battery cable. Remove fan shroud. Remove fan and accessory drive belt. Drain cooling system.
2. Remove crankshaft balancer bolt. Remove crankshaft pulley bolts and crankshaft pulley. Using Damper Puller/Installer (J-39046), remove crankshaft balancer.
3. Remove all mounting brackets and coolant hoses attached to water pump. Remove water pump.
4. On models equipped with a Crankshaft Position (CKP) sensor, disconnect CKP sensor harness connector. Remove CKP sensor holddown bolt and CKP sensor.
5. On all models, loosen or remove oil pan as necessary for removal of front cover. Remove front cover bolts, front cover and gasket.
6. On models equipped with a CKP sensor, remove CKP sensor reluctor ring. (Scheme 7)
7. On all models, rotate crankshaft until timing marks on camshaft and crankshaft sprockets are aligned. (Scheme 8) Remove camshaft sprocket and timing chain. To remove crankshaft sprocket, use Sprocket Puller (J-5825-A).

1. Install Woodruff key in crankshaft (if removed). Using Crankshaft Sprocket Installer (J-5590), install crankshaft sprocket. Install camshaft sprocket and timing chain. Ensure timing marks on sprockets are aligned. (Scheme 8) CAUTION: On 4.3L with balance shaft, the timing gear sprocket marks align at TDC of cylinder No. 4.
2. Install and tighten camshaft sprocket bolts to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000).
3. On models equipped with a CKP sensor, install and align CKP sensor reluctor ring. (Scheme 7) On all models, install front cover using NEW gasket. Tighten front cover bolts to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000).
4. On models equipped with a CKP sensor, install CKP sensor. Tighten CKP sensor holddown bolt to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000).
5. On all models, apply RTV sealant to Woodruff keyway in crankshaft balancer. Using Damper Puller/Installer (J-39046), install crankshaft balancer. Install crankshaft pulley. Install crankshaft balancer bolt and crankshaft pulley bolts and tighten to specification. See «TORQUE SPECIFICATIONS»(ref-50103-S06511345062001011600000). To install remaining components, reverse removal procedure.

Scheme 7

Scheme 8