In which engine configurations does the camshaft act directly on the rocker arms without a pushrod?

In which engine configurations does the camshaft act directly on the rocker arms without a pushrod?

• A. Pushrod Engine
• B. Single Overhead Cam Engine & Dual Overhead Cam Engine
• C. Cam-in-Block Engine
• D. Overhead Valve Engine

Answer: (B)

The important idea is where the camshaft sits and how it drives the valves. In overhead cam designs, the camshaft is in the cylinder head and its lobes operate the valve through direct contact with followers or rocker arms, so no pushrod sits between the cam and the rocker. That’s why single overhead cam and dual overhead cam engines fit this description—they use one or two camshafts in the head to directly actuate the rocker system that opens the valves. In contrast, pushrod engines place the camshaft in the engine block and transmit motion up to the rocker arms via pushrods, so a pushrod is part of the path from cam to valve. The term cam-in-block and the common designation overhead valve refer to that pushrod/ OHV arrangement, not to an overhead-cam setup.

The important idea is where the camshaft sits and how it drives the valves. In overhead cam designs, the camshaft is in the cylinder head and its lobes operate the valve through direct contact with followers or rocker arms, so no pushrod sits between the cam and the rocker. That’s why single overhead cam and dual overhead cam engines fit this description—they use one or two camshafts in the head to directly actuate the rocker system that opens the valves.

In contrast, pushrod engines place the camshaft in the engine block and transmit motion up to the rocker arms via pushrods, so a pushrod is part of the path from cam to valve. The term cam-in-block and the common designation overhead valve refer to that pushrod/ OHV arrangement, not to an overhead-cam setup.