I’ve noticed on early engines (4 stroke) that the cam controls the exhaust valve only. The inlet valve has such a weak spring as to defeat it’s seat when the piston draws down on its inlet stroke, allowing a fresh charge of air. only to drive it into a sealing position upon ignition & higher cylinder pressures closing both. I know it seems weird, However, some of these low revving engines lasted for decades. they swapped HP for torque with large flywheels.
Bulgarian Umbrella said:
I’ve noticed on early engines (4 stroke) that the cam controls the exhaust valve only. The inlet valve has such a weak spring as to defeat it’s seat when the piston draws down on its inlet stroke, allowing a fresh charge of air. only to drive it into a sealing position upon ignition & higher cylinder pressures closing both. I know it seems weird, However, some of these low revving engines lasted for decades. they swapped HP for torque with large flywheels.
Yep, they’re called an atmospheric inlet valve. If you don’t need much power nor efficiency they work.
Bulgarian Umbrella said:
