Foamy head

Taylor Made R7 Driver (4 weight screws) had developed a rattle inside the head. Removal of the weights was unsuccessful in removing the offending piece of noise. So I decided to fill the head with expanded polystyrene foam. The head no longer rattles, and produces more of a 'donk' than a 'ping', but hasn't affected the club detrimentally except for maybe it's a bit easier to fade.

Is this legal (from a golf rules POV) ?

Absolutely.

However, when you decide to remove the foam later, DON'T use heat (or you'll likely have a flaming head).

In the future, you can use a plumbers torch or other heat source to heat up the bottom of the head. Almost all driver heads today have some rattle stop in them to catch weld beads or other foreign material that can end up in the head during the manufacturing process to create a rattle. Heating the sole liquefies the rattle stop, then you shake the head until the rattle stops, then allow to cool. Serves 4.

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Cotton or polyfil does the same thing - even adding more hotmelt helps. The thing to be careful about is headweight and thus swingweight/MOI.

Thanks LowPost . I now know for the next time I or someone else gets a noisy head. In the meantime though, my ears should be safe from damage.