What size valves are on a Boss 302?
The original Boss 302 engines used intake valves about 2.02 inches in diameter and exhaust valves about 1.60 inches in diameter. These measurements come from the high-performance heads Ford used on the 1969–1970 Boss 302, which featured a 4.00-inch bore and 3.00-inch stroke. Note that reproduction or aftermarket heads can vary in valve size, so verify the specific casting when restoring or building a Boss 302 engine.
Context: the Boss 302 engine and its valve sizing
The Boss 302 was Ford’s Trans-Am racing-derived 302 cubic inch V8, designed for high-rpm performance. Built for 1969 and 1970 Mustang models, it combined a 4.00-inch bore with a 3.00-inch stroke to reach roughly 302 cubic inches. To maximize breathing at elevated engine speeds, the Boss 302 used specially engineered cylinder heads with larger valves compared with standard small-block Ford heads of the era. The valve sizes cited here reflect the original Boss 302 heads commonly documentation in period sources and restoration references.
When rebuilding or sourcing parts, the exact valve dimensions can depend on the head casting number. Some restoration shops and aftermarket head suppliers produce Boss-302-appropriate heads with slightly different valve sizes, so it’s important to confirm your specific head’s measurements before finalizing parts orders.
Original valve sizes in the Boss 302 heads
The following valve sizes correspond to the original Boss 302 cylinder heads used on 1969–1970 production cars:
- Intake valve diameter: 2.02 inches
- Exhaust valve diameter: 1.60 inches
These dimensions illustrate the performance-oriented nature of the Boss 302’s head design, aimed at improved flow at high RPM. If you are restoring a Boss 302 or building one from parts, cross-check the head casting number to ensure you’re matching the intended valve sizes, and consult contemporary Ford service literature or reputable restoration resources for verification.
In summary, the Boss 302’s original valve sizes are approximately 2.02 inches for the intake and 1.60 inches for the exhaust. Variations may exist in reproduction or aftermarket heads, so confirm the exact measurements for your specific heads before ordering components.
Summary: Boss 302 engines originally used a 2.02" intake valve and a 1.60" exhaust valve. Always verify the head casting number when purchasing parts, as reproductions can differ.
