Q: How to replace broken valve springs or defective valve stem seals without remove the cylinder head?
A: In order to replace broken valve springs or defective Valve Stem Oil Seals without removing the Cylinder Head, specialized tools and compressed air are usually used. To start with, remove Rocker Arms and shafts from cylinder heads and the spark plug from the affected cylinder. Place the piston of the faulty cylinder at top dead center on its compression stroke, starting with cylinder number one if replacing all Valve Stem Oil Seals and proceeding through the firing order. Thread an adapter into the spark plug hole and connect it to a source of compressed air after observing safety precautions. Or else, place the piston near TDC on the compression stroke if compressed air is not available and put a length of nylon rope through the spark plug hole to hold up the valves. After that, do not let anything fall into engine parts or tools while using a valve spring compressor to compress spring for removal of keepers. Take out spring retainer, valve spring, and Valve Stem Oil Seal noting any possible damage to valve face or seat. Wrap around valve stem, release air pressure or rotate crankshaft as appropriate then examine valve stems for damage. Re-apply air pressure after removing any obstructions; lubricate valve stems and put in a new Valve Stem Oil Seal. Finally, reinstalling rocker arms as well as shafts, spark plug(s), and camshaft cover followed by necessary engine checks for leakages or unusual sounds in rocker arm cover area.