lock angle and 3/8" valve stem size are a perfect replacement lock for stock engine rebuilds. They are recommended only for street Applications with lighter valve spring loads. It is critically important to make sure valve locks match the valve size. There should always be a small gap between the two halves of the lock when they are properly positioned on the valve stem. If the two halves fit together without a gap, they are too large. If the locks fit tight to the stem and leave a gap between the middle of the lock and the OD of the stem, the locks are too small. Most people believe that the tang inside a valve lock Oldsmobile the retainer and valve spring in place while the engine is running. This is not the case. The cross-section of material in the tang is not strong enough to withstand open spring loads of 1000 lbs. or more. The sole purpose of the tang is to temporarily locate the lock, retainer and spring relative to the valve until the taper of the retainer can nest around the outside surface of the lock. This creates a "collet" effect that binds the two together. The more spring force exerted on the retainer (as the valve opens), the more force applied by the "collet" effect to keep the retainer and lock in place.