Volvo 530 head castinng variants

Hello,

Does anybody know what is the purpose of this indent inside the 530 head.

Is a 530 head from 93 non turbo (740)

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

which is also 530 head from 91turbo (740)

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

Got Knock? - see: Viatrack Printed Circuit Designs

Ontario