Chevrolet 12453265 Cylinder Head Assembly

You can Select Your Vehicle to check if 12453265 fits your vehicle.

Before removing the valves, it is important to label and store them, along with their related components, so they can be kept separate and reinstalled in the same valve guides they are removed from.

After compressing the springs, install the lower groove seal if using the flat O-ring type, ensuring it lies flat and not twisted. Position the keepers in the upper groove and release the compressor, making sure the keepers seat correctly.

If they are in good condition, reassemble the valve train components in the cylinder head without major servicing.

To remove the cylinder heads, begin by removing the rocker arm covers, followed by the intake manifold, ensuring that the cooling system is drained to prevent coolant from entering internal engine areas when the manifold and heads are removed. Detach both exhaust manifolds and then proceed to remove the rocker arms and pushrods. Using a new head gasket, create a template by outlining the cylinders and bolt pattern on a piece of cardboard, ensuring the front of the engine is indicated for reference and punching holes at the bolt locations. Loosen the head bolts in 1/4-turn increments until they can be removed by hand, working in a reverse pattern of the tightening sequence. Store the bolts in the cardboard holder to retain their original positions. Lift the heads off the engine using caution, and if resistance is encountered, avoid prying between the head and block to prevent damage to mating surfaces; instead, use a block of wood and a hammer to dislodge the heads. Store the heads on blocks of wood to protect the gasket sealing surfaces. For installation, the cylinder head and block mating surfaces must be thoroughly cleaned by using a gasket scraper to remove carbon and old gasket material, followed by cleaning with lacquer thinner or acetone. Ensure there is no oil on the mating surfaces, as it may lead to improper gasket sealing and potential leaks. Check the mating surfaces for damage and address it accordingly, either by filing minor imperfections or machining for excessive damage. Chase the threads in the head bolt holes with the appropriate tap and clean the threads thoroughly. Position new gaskets over the dowel pins in the block, and if using a steel gasket, apply a thin coat of sealant to both sides before installation, ensuring the raised bead faces up. Composition gaskets should be installed dry without sealant. Carefully position the heads on the block without disturbing the gaskets. Prior to installing the head bolts, coat the threads with a non-hardening sealant like Permatex no. 2, then install the bolts in their original locations and tighten them finger-tight. Follow the recommended tightening sequence, gradually torquing the bolts to the specified torque. Complete the installation by following the remaining steps in reverse order.

Thoroughly clean the cylinder head and block mating surfaces by using a gasket scraper to remove carbon and old gasket material, followed by cleaning with lacquer thinner or acetone.

The cylinder head cleaning and inspection process should be started after completing the engine disassembly procedures, if a complete engine overhaul is being done.

Install the rocker arms and pivots on the cylinder head studs, threading the nuts a few turns only.

Clean the rocker arm pivot stud threads, cylinder head, rocker arms, pushrods, valve springs, shields, keepers, and retainers with solvent and dry them thoroughly.