Originally Posted by
Stu @ M Developments
Its quite a common problem guys, I have never heard a good enough reason to believe why some blocks expand more than others although I suspect that oil/coolant temperature variations between engines and previous overheating will be an issue if its ever examined carefully, but the fact is this is a known problem, we used to have them brought to us at Ford when brand new with noisy cambelt / cover interference.
Tensioning them backwards causes a seperate problem, but its a problem all the same, I suspect in this particular case that one of your cars is tensioned backwards causing the stat housing interference you mention.
Regardless: Tension the belt when fully hot using a strain gauge and pull it to teh right hand side oof specification. remember, this chap isnt in the UK, when he says cold he desnt necessarily mean its only 10Deg C. LOL
I definitely have both tensioners on both cars tensioned in a clockwise rotation and the reason it hits the housing is the "flapping" motion of the slack belt not because the belt is routed differently i.e. if it were tensioned anticlockwise. It's not cold yet we are at +6C but Christmas will be -20C and January will be in -40C, February HELL freezes over!!