KNOW WHAT WILL HAPPEN IF YOU BLOCK YOUR ENGINE EXHAUST !!

If someone blocked it successfully the engine would stop because it can't expel the exhaust gas on the second stroke of the piston.Damage to the engine would be highly unlikely.The engine is basically a big air pump. Air is drawn into the engine through the air filter and the fueling system by the movement of the pistons. As the piston moves down, valves open on the air filter side allowing air to fill the piston. As the piston move back up after compression and ignition, the valves on the exhaust side open allowing the air to be pumped to the exhaust system. If the exhaust system won’t allow any air out, the engine won’t run as it won’t be able to draw air and fuel into the engine. Air has to have somewhere to go for it to flow.