Valve clearance changes on opposed-type engines using hydraulic lifters are accomplished by?

In opposed-type engines that employ hydraulic lifters, the method by which valve clearance is adjusted stems from the design and operation of these lifters. Hydraulic lifters are designed to automatically adjust to maintain the correct valve clearance under various operating conditions. They use oil pressure to fill an internal chamber, compensating for wear and thermal expansion.

When valve clearance needs to be changed due to maintenance or wear, it is most effectively and accurately addressed by the adjustment of the hydraulic lifters themselves. This adjustment ensures that the lifters remain self-adjusting, maintaining the appropriate clearance without the need for additional hardware changes.

While rocker arm adjustments or replacements could theoretically influence valve clearance, they do not directly provide the necessary precision and maintenance changes that hydraulic lifters are specifically designed to manage. Push rod replacement is also not a correct method for adjusting valve clearance since the relationship between push rods and the hydraulic lifters already fulfills the necessary operational requirements designed into opposed-type engines. Therefore, adjusting the hydraulic lifters is the appropriate and efficient method for maintaining and changing valve clearance in these engines.