I thinned my HHR fan out about as much as you possibly can to squeeze it in the BBR.

Although the HHR fan is not overly deep at 4", the BBR needed it to be thinner to fit in between the water pump snout and the radiator. I test fit it and while it *did* fit, the back of the shroud behind the motor was just touching the water pump pulley.

So I did what any good gearhead does. I took a brand new part and started taking it apart. Upon close inspection I decided that the plastic area behind the motor could safely be removed. Removing this plastic (outlined in yellow) will give a net gain of 1/2". The back of the motor only sticks out 1/4" past the lip marked with a red arrow.



Next thing to be removed is the little locating tabs. They are 1/8" tall. Grind these off flush.







It's very cozy in there, but it fits and keeps the temps down. This is a 11.6:1 545" motor with a 19x27 radiator.