I think that most older overhead valve engine have enough clearance that unless the valves come out of their guides they cannot impact the pistons. I was hoping the Savage engine was an old enough design to be non-interference. Below is an excerpt from a wiki on timing belts that describes the difference between interference and non-interference. But in the case of the cam chain it sounds like the valves are not the main issue, but the issue is the chain dropping down into the engine and causing havoc.
Quote:Depending on the design of the engine, the piston and valve paths may "interfere" with one another and incorrect timing in their movements may result in the piston and valves colliding. (Such designs are also called "interference head" or "interference engines", and include virtually all diesel engines. Conversely, non-interfering engines, such as the Mazda B engine, are called "free-wheeling" or "non-interference" engines.)
In interference designs, regular service is especially important as incorrect timing may result in the pistons and valves colliding and causing extensive engine damage and therefore costly repairs. The piston will likely bend the valves or if a piece of valve or piston is broken off within the cylinder, the broken piece may cause severe damage within the cylinder, often also affecting the crankshaft. Some manufacturers, such as Nissan, have switched back to timing chains for the majority of their engines because of the breakage problems associated with belts. However, in some newer engines, timing belts are designed to last the effective life of the engine. Other manufacturers, such as Toyota, use a mix: timing chains on their interference engines and timing belts on their non-interference engines.
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