if it's cutting off spark i assume it's cutting off fuel too or there would be unburned fuel in the cylinders.

when i mentioned cutting off fuel above i assumed that meant no spark either as that would be pretty pointless.

 

both of these are good reasons for the sound, not an actual description of what the sound consists of....the atkinson cycle in operation on our v8's shuts down cylinders when
the power is not demanded, to about 4 i believe, which is why we get such good mileage ...and no clattering is heard...so its clearly not just fuel/spark shutoff creating the clatter...
sound like some type of relief valve...

 

Atkinson has NOTHING to do with cylinder deactivation, and also a the LC V8 DOESN’T shut down cylinders.

 

yeah, i just read up on atkinson on wikipedia, so evidently i'm full of it... however, do you know what makes the sound we are discussing ? all participants have
fervently offered their take on the reason for the sound, but its actual source remains a mystery...i cant believe they'd let the pistons and valves clatter like a
couple dozen wind-up false teeth goin off all at once....any ideas ?