Sunday, March 9, 2008

Tech Tip- Valve Lash Adjustment

Valve Lash Adjustment

The 292 and 312 cubic inch engines are the standard engines for the 1955 through 1957 Thunderbird. These engines are equipped with mechanical valve lifters which require periodic maintenance to maintain the correct valve lash setting of .019 (nineteen thousandths of an inch). The maintenance to the valves is considered routine, yet it is the most frequently overlooked maintenance procedure. Improperly set valve lash will create a "clattering noise" which will be most noticeable at idle speed. Unless you are familiar with the workings of the internal combustion engine, you should not attempt to adjust the valve lash yourself. The information in this article, however, will provide your trusted service technician with the appropriate information needed to adjust the valves correctly. Improper adjustment of the valves can result in damage to the valves and the engine.

The following reference information was obtained and submitted by Ken Smizinski and can be found in the book entitled Fix Your Ford by Bill Toboldt, copyrighted 1971:

"To adjust the valves on the V-8 engines with mechanical lifters first locate the timing marks on the vibration damper, and make three chalk marks, each spaced 90 deg. from the timing mark, so that the damper is divided into four equal parts. On the 272, 292, and 312 cu.in. engines which have mechanical valve lifters, and a firing order of 1-5-4-8-6-3-7-2, crank the engine until No.1 piston is near top center on the end of the compression stroke and adjust the following valves: No.1 exhaust, No.4 exhaust, No.5 exhaust, No.1 intake, No.2 intake, No.7 intake. Rotate the crankshaft 180 deg. or one-half turn which puts No.4 piston on T.D.C. then adjust the following valves: No.6 exhaust, No.8 exhaust, No.4 intake, No.5 intake. Rotate the crankshaft 270 deg. or three-quarter turn from 180 deg. which puts No.3 piston on top center, then adjust the following valves: No.2 exhaust, No.3 exhaust, No.7 exhaust, No.3 intake, No.6 intake, No.8 intake. Valve lash should be adjusted to specified value."

The above procedure is best done with the engine off. To check the valve lash settings after adjustment, however, the engine must be running at idle speed. Allow the engine to run thirty minutes before checking the valve lash. The valve lash should be .019 with the engine running at idle speed.

source: CTCC Tech-Tip Manual 1993-1997

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