Zahid,


The spinner nut, or the spinner may be a lot heavier than the propeller.
But its dimensions are such that it has weight very close to the center of the prop shaft.

This means it would have very inertial effect on the engine; slowing its transition by a smaller amount than would an 8" glass filled nylon APC prop.

The use of these heavy spinner nuts is to balance tail-heavy models, by putting the balancing mass as far forward as possible. This heavy nut at the very front of the plane, has the greatest effect since it is furthest from the model's axis of rotation.
But in the case of the engine. it is closest to its axis of rotation.

You would need a very un-balanced nut, and/or bent crankshaft front end, and/or loose threads that allow the nut to cock, putting it out-of-line with the crankshaft center-line, to feel any effect.