Ok here's the story I bought a motor which is a 468bbc and I dropped it in my car a few days ago and went to install the harmonic balancer and found out someone had tapped the hole out! A 5/8" 18 thread bolt is to big and a 9/16 18 thread bolt is to small! So it has to be milimeter! Someone told me it's got to be a 14 or 15mm fine thread and these bolts are used on bseries and kseries motors? Someone please help me! The machine shop I picked the motor up from mostly worked on inports so that explains why they would tap it out to a milimeter bolt. I dont have the name of the shop or number sobi can't call them! And it's a long ways away from where I live. Somebody please help me! The bolt needs to be about 1.5long.