GMC 11588728 Hold Down Clamp Bolt

Valve springs break and valve stem seals can be changed without removing a cylinder head, generally, two special tools and compressed air. First, the spark plugs and valve covers shall be unplugged and by turning the crankshaft of the vehicle, the piston number one should be on the compression stroke TDC. Take out the rocker arms for the number one cylinder, insert an adapter into the spark plug hole and attach an air line from compressed air. Using compressed air jam the valves on the cylinder and for the cylinder head hole stuff the shop rags so as to avoid oil and other parts or tools to fall on the engine. Lightly hammer on the heads of the valve springs with a soft-faced hammer to free the valve keeper from its seat on the spring retainer with a magnet or with small needle-nose pliers using a valve-spring compressor. Lift off the valve spring and the retainer and if air pressure cannot keep the valve closed the valve face or seat may be bent and will require the cylinder head to be pulled for repairs. Take out the previous valve stem seals with the typical variation between the intake and the exhaust seals and circle the head of the valve stem with a rubber band or some piece of thin tape so as the top of the valve stem won't fall off into the combustion chamber before one can release the air pressure. Check the valve stem for signs of wear particularly the smooth running of the stem in the guide; if this fails the head will have to be unbolted for further repair. Pump in a little air pressure to lock the valve in its closed position; then, place the new valve stem seals over the ends of the intake and exhaust valve guides. Place the keepers alongside the retainer and over the valve, compress the valve spring assembly enough through to seat the keepers and use a drop of grease just to ensure that they are well in place. Retract the keepers and take off the pressure from the spring tool, thereafter, take off the air hose and remove the adapter from the spark plug hole. Perform the same on the other cylinders, with each piston at TDC on the compression stroke when air pressure is applied and the rocker arm assemblies and valve covers fitted back.