Volvo 530 head differences

Hello,

I have been asking this one for a while and no one seems to have the answer.

Does anybody know what is the purpose of these indents inside the 530 head.

the indent on the side opposite to the sparkplug is much smaller than in

1. Are the indents different because one head was on a non turbo (smaller indents) and the other two were on a turbo.

1. Are the indents different because they updated the molds?

2. Why are they there in the first place?

Regards,

Boris Mohar

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