GM 14095451 Valve Assembly, Exhaust

The valve mechanism of the 231 cu in V6 engine is peculiar because it does not have a valve lash adjustment provision like most GM engines. If the valve seat on the cylinder head or the valve face is ground it alter the height of the valve stem from the surface of head. GM says that if valve and seat have been refinished to such an extent that the end of the valve stem will be 0.050 inch higher than in its normal position, the required correction must be made by grinding off the stem end to bring valve stem back to standard height. First, take off the cylinder head and put it aside on a clean flat surface which will be referred to as surface A. Using a good spring compressor like; GM tool J-8062 compress the valve spring to remove the valve spring cap key, and after that ease of the tool to pull out the spring and cap off. Take out and dispose the valve seals stacking the valves in order in a block of wood or a hard cardboard for replacement. Wash and inspect the cylinder head for signs of damage, it is also important that one checks on the valves for pitting, the burnt marks as well as seating; the valves shall be re-condition or replaced, if a valve after re-grinding has sharp edge, it should be chucked away. The increment in the valve lift, as observed on the stick at the valve stem end, causes the clearance in the guide if excessive; to rectify this will require the installation of an oversized valve and should be done at the dealer or machine shop. Because the valve seats should be trued up to 45° in the refining stage, valve lapping should not be done. Coat the stems and guides with engine oil prior to reinstalling the valves, and replace intake valve seals, but do not use new exhaust valve guide seals. Go over the valve stem slowly and let the flattened part of the valve seal come to rest atop the valve stem, then use some installation tool such as the GM tool J-22509 to slide the valve seal over the valve guide in a way that the upper inside surface of the said valve seal reaches the top of the valve guide. Squeeze the springs only to assemble keepers since tightening the valve's seal can be affected when the springs are compressed tightly. Lastly re-attach the intake and exhaust valve springs as they can be placed in upside down manner then re-attach the valve spring, cap, and cap retainer and finally the cylinder head.

Generally inspect the heads of the valves for pitting and burning especially the exhaust valves In addition inspect the valve seating. Certainly if pitting is minimal it should be possible to rectify this by grinding the seats and valves together with coarse and fine valve grinding paste. To grind the valves, smear a little coarser carborundum paste on seat face and suction grinder tool on the valve head, in a semi-rotary motion and now and then lifting the valve to spread the paste evenly. After a matte finish is acquired on both surfaces, remove the paste and go back to using extra fine carborundum paste; as the valve is turned and lifted as necessary. This may be eased with the use of a light spring put under the valve head. When there is a continuous ring of light grey matte finish on both faces the grinding is done. If pitting or burning is more than light, the valve should be refaced by the dealer with the seat recut; if the head edge rubs are low after skimming, then you have no option, but to change the valve. Last, all carbon must be wiped off the valve head and stem, no grind compound should stay in the ports or in the valves guide and valves and seats should be cleaned to perfection with solvent soaked rags, clean rags and lastly, if available blow with an air line.

It is important to scrape away all carbon from the valve head and stem, then clean the valves and valve seats using a solvent-soaked rag followed by a clean rag.

The valve seats should also be trued up to 45°, which is another job for a dealer or machine shop.