[Freedom4US]

Timing belts are also critical in one other important aspect -- many, though not all, OHV/C engines are of an 'interference' design -- if the belt breaks or slips pistons will physically strike valves as the timing shifts radically. If this is the case prudence and thrift dictates you should look for a new or rebuilt engine, as the cost for repair is vanishingly close to a complete replacement apart from the longterm reliability of the repaired engine.

[Petronski]

Timing belts are also critical in one other important aspect -- many, though not all, OHV/C engines are of an 'interference' design -- if the belt breaks or slips pistons will physically strike valves as the timing shifts radically...

Excellent advice, but please, tell us what kind of engine you have, and I can look up whether it is an 'interference' type.