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…

In this instance, ‘free-wheeling’ means ‘non-interference’. However, I was taught that ‘free-wheeling’ refers to Diesel engines, in that they have no throttle plate on the intake system, and therefore not much resistance to keep the engine from spinning when the gas pedal is released, unlike the eng…

“Free-Wheeling” means that if the cam belt or timing chain snaps or jumps, that even if the cam stops turning with some valves open and extended down into the cylinder, that the engine is designed so that there is enough clearance that the pistons will not hit them. “Interference” means that the en…

Free-wheeling is more of a mechanic slang term and the source of that info should probably not have used it to replace the non-interference term. If they’re going to use the free-wheeler phrase then it should have been paired up with non-free-wheeler to prevent any confusion.

Free wheeling means that if the timing between the pistons and valves is lost due to a broken timing belt/chain, the engine is free to spin or wheel without interference. Interference means the opposite. Tester

Slightly off topic, but a long time ago SAAB used to have a free-wheeling mechanism in their manual transmissions. There was a lever underneath the dash and the mechanism could be turned on or off as desired. This would allow a car to coast without engine braking similar to coasting in neutral. Th…

Continuing off topic about free wheeling, the first Saabs had it as ok4450 describes. The reason for providing it was because they had two cycle engines that did not have oil injection but instead, the engine lubrication oil was mixed with the gasoline. On a long downhill with the throttle closed,…

@Ok4450 No off topic for you. That 's the first thing I thought of having owned a SAAB two stroke many, many years ago. The reason you needed it was, if the motor was allowed to turn through the drive wheels with little,or no throttle, it was getting no engine lube through the gas oil mix which sho…

I didn’t see to many of those old SAABs but they did come into the dealer on occasion. My memory is very hazy on this but I’m pretty sure the SAAB Sonnetts with the Ford 4 stroke V-4 engines also had the free wheel mechanism.

What does "Free Wheeling" mean, compared to "Interference"?

Maintenance/Repairs

George_San_Jose1 January 27, 2013, 5:48am 10

Thanks for the explanation everyone. Seems like “free wheeling” and “non interference” are interchangeable for the most part, esp when referring to gas engines in modern cars.

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What does "Free Wheeling" mean, compared to "Interference"?

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