Below is some data on Mazda engines for purposes of illustration. This nomenclature confuses me. I always thought an engine was either “interference” or “non-interference”. " Non-interference" I thought meant the valves are separated enough from the pistons that the valves can never collide with the pistons even if the valve timing goes askew. “Interference” I thought meant the valves could possibly collide with the pistons if bad valve timing (caused by a broken timing belt say) causes a valve being pushed down by the camshaft at the same time when the piston was coming up. Bang. $5000 repair bill. No good.
But the data below separates these Mazda engines into “Interference” and “Free Wheeling”.
What does “Free Wheeling” mean? How is it different from “Non-interference”?
1.8L 4 Cyl. Free-Wheeling
1.8L V6 Free-Wheeling
2.0L Diesel Interference
2.0L DOHC (626, MX-6 & Protege) Interference
2.0L DOHC (Tribute) Free-Wheeling
2.0L SOHC Free-Wheeling
2.3L 4 Cyl. (B2300) Free-Wheeling
2.3L V6 Free-Wheeling
2.5L 4 Cyl. (B2500) Free-Wheeling
2.5L V6 Free-Wheeling
3.0L DOHC Interference
3.0L SOHC Interference