Genuine 2002 Chevrolet Astro Cylinder Head

2002 Chevrolet Astro Parts Questions & Experts Answers

• Q: How should a Cylinder Head be prepared for reassembly after valve servicing on 2002 Chevrolet Astro?

  A: Even if a head goes to an automotive repair shop for valve servicing, assure it is clean before reassembly is done. If a head was removed for valve refurbishing, the valves, and associated hardware will be installed, proceed with the reassembly in the following manner. Wipe the valve stem with moly-based grease or clean engine oil, then, place the first valve on the head, beginning from one end, having a tennis ball under the head to hold the valve while setting the seal. There are three different valve stem oil seals depending on the year of production, engine type and size : small O-ring, the flat O-ring which is a less common, and the umbrella type of seal. On later 1998 and newer models, EX is molded into the top of a new exhaust valve oil seal , and this seal is either brown with a white stripe, or solid red, and is not interchangeable with black intake valve seals. Place the new valve seal over the guide and insert an appropriate tool to use as a hammer to over tighten the seal on to the valve guide. Attach the damper spring, valve spring, oil shield and spring retainer or rotator depending on the type of the valve. Use an appropriate compressor to compress the valve spring(s), then if used, apply some grease to the flatted O ring and place it in the lower valley of the valve stem as shown below. Slip a drop of grease on the keepers, insert them into the upper groove of the stem of the valve, and then gradually let the compressor side go while it holds the keepers. Do the same for the rest valves, making sure every embody to its place. All valves must be installed, then it is good practice to inspect the stem O-ring seals for leakage which is perhaps better performed by an expert with the aid of a vacuum pump and adapter. If the vacuum cannot be maintained the seal is leaking and has to be checked out or replaced before attaching the head to the engine. Check the installed valve spring height with ruler or dial caliper to measure that it is set right; if it is more than needed, get thin shims and place them under the springs, but do not shim the height under the specified limit. Last of all, sequentially, spread a layer of moly-based grease on the upper face of the rocker arms and the lower side of the pivot balls, next, with the cylinder head studs in position, fit the rocker arms and the corresponding pivots for the pushrods to be tightened when the heads are on.