Valve engine problem Brisbane - BURNT

There are many reasons for burnt out valves. Some times it is a combination of reasons but it is generally easy to determine the major cause. Weak valve springs: check valve spring tension and free length also check installed height. Low seat height: check valve installed height and valve recession. Worn valve guides: check guide wear.( using a new valve as a gauge is the simplest method) Worn valve stems: measure valve stem in all positions of wear.(micrometer is the best method) Incorrectly set tappets: this can only be determined before strip down. (hydraulic tappet depression should also be checked) Incorrectly faced valves: check valve face finish. (finish should be fine without any chatter or flats) check valve for run out. Check for correct face angle. Should be 1 degree different, to allow contact at top side of seat. Incorrectly cut seat: seat contact position on a valve should be around .1 to 1.5mm away from the valve margin.(the centre third of the valve face )  Incorrect seat width: The seat contact width is generally between 1 and1.5 mm. Generally three angles are involved in seats. Check the seat angle is either 45 or 30 degrees, with a top cut angle of 30 or 15 degrees and a throating angle of 70 or 0 degrees. Concentricity: The concentricity of the seat to the guide has to be checked.(using bearing blue, or vacuum tester) Incompatible fuel for engine: LPG used without any head modifications if required, ULP where super or premium should be used. Incorrect ignition timing: driving vehicle at sustained high revs while the ignition timing is incorrect will contribute to burnt valves. Excessive combustion temperatures will cause exhaust valves to burn.( check base ign.timing and full advance timing.) Incorrect fuel mixture: incorrect fuel mixture can increase the combustion temperatures to a point where sustained driving will burn valves. Poor oil control: Build up of carbon on the valve stem or seat prevents correct seating to take place resulting in poor heat transfer from the valve head to cooling system. A general over view is that some of the causes listed can produce burnt valves on their own, while it is quite often a combination of a number of these causes that ultimately results in the burnt out valve. Disclaimer Agreement : Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines