🔍 Key Concepts

• Main starting air valve vs. pilot valve in cylinder head air-start systems • Difference between direct mechanical actuation and air‑pressure (pilot) actuation of the main valve • Purpose and location of a distributor in multi‑cylinder starting systems

💭 Think About

• Trace the mechanical linkage in the illustration: what does the cam and pushrod (III) actually open—does it lift the big valve in the head directly, or a smaller valve in a separate body? • Follow the air path: when the small valve opens, where does the air go, and how does that cause the large valve (I) in the cylinder head to open? • Look for any rotating or multi‑outlet component that would send air to several cylinders in sequence—do you see such a distributor anywhere in this figure?

✅ Before You Answer

• Verify whether the camshaft motion is acting directly on the main starting air valve in the head, or only on a smaller control valve lower down. • Check if there is a separate small valve (pilot) that first admits air to a chamber above the main valve to lift it, instead of the pushrod lifting the main valve itself. • Confirm that there is no rotating distributor block shown and consider what that tells you about whether this is a distributor type system.