What is the difference between an interference and a non interference engine?

Answer 1

Piston to valve clearance.

In the event of a cam belt or timing chain failiure

an engine classed as interference wil suffer considerable damage

when the belt/chain fails the valve timing goes out of sync

which causes the valves to contact the pistons,

resulting in bent/broken valves, possible damage to the valve guides located in the cylinder head, and very rarely damage to the pistons.

A non interference engine,also known as a freewheeling or safe engine.

In the event of belt/chain failiure, the valves do not meet the pistons

I:E the engine fails safe

A precautionary compression test should be carried out after belt/chain replacement

to check condition of the valves.

best wishes