This adjustment is required only on the 6-198, 6-251 and 1967-80 6-225 engines. It need not be done at every tune-up, but should be done whenever there is excessive noise from the valve mechanism, or at least every 20,000 miles (32,186 km).
No valve lash adjustment is necessary or possible on any other Chrysler-built engine. Hydraulic valve lifters automatically maintain zero clearance. After engine reassembly, these lifters adjust themselves as soon as engine oil pressure builds up.