Non-Interference Engine

[morfirst]

Does anyone know if the 240Z engine is a non-interference engine? In other words, if the timing chain breaks, no damage will occur between the valves and pistons.

[2ManyZs]

I didn't know there was such a thing as a non-interference engine.

I've seen timing chains break on everything from four cylinders to V-8's and they will all slap a valve if it breaks. I've seen some Chevy V-8's bend every one of the exhaust valves at the same exact angle when the timing chain let go.

[jcdozier]

Like 2ManyZs, I didn't know there was such a thing as a non-ineterference engine until a few weeks ago. Whilst at a Goodyear store with my son I saw a wall-chart listing interference and non-interference engines. Unfortunately, the early Z engines weren't listed, so I don't know the answer to your question.

[jcdozier]

I didn't know there was such a thing as a non-ineterference engine until a few weeks ago. Whilst at a Goodyear store with my son I saw a wall-chart listing interference and non-interference engines. Unfortunately, the early Z engines weren't listed, so I don't know the answer to your question. Since Goodyear had the chart, maybe your local dealer can answer??

JIM DOZIER

[morfirst]

I'll try to find out. I have the original maintenance manual for my 72, if I look hard enough I may be able to find the answer. My guess is that it is an interference engine. But the risk should be minimized considering it is a timing chain as compared to a belt.

[2ManyZs]

Well, perhaps there is such a thing but it may boil down to whether any major damage is done or if it is so slight it doesn't hurt the engine.

I believe it would all have to do with valve angle and size versus the piston deck height. It would be possible to make a "non-interference" engine into one with little problem. Head decking, cam change with more valve lift, piston dome or pin height, rod length, stroke, larger valves all figure into the equation along with quite a few other modifications that are possible.

I believe the totally stock L engines would possibly be in the non-interfernce category, but that doesn't mean that the valve won't hit the pistons, it may be that they don't cause any major damage. I don't think I have heard of anyone breaking a timing chain on the L engine and having any major piston damage. It is possible the piston deck height is low enough as to not cause any damage. But if you take a stock bore L block and put larger valves in, the valves will hit the block, therefore the block needs to be "eyebrowed" between the cylinders. So in that regard there really is no such thing as a non-interference engine.