I'm in the middle of tearing apart my engine to replace the timing chain guides, and I've read on the forum that sometimes the crank pulley hex socket screws can shear.

so I decided to go ahead and replace the six of them with new screws. this began a journey into learning about hex socket screws.

I went down to my local ace hardware, and comparing my original screw it turns out these are M8 (8mm thread) x 30mm (length) and 1.25mm pitch.







They were listed as "grade 8.8". huh?

turns out metrics strength grades are different. standard fasteners range from grade 2 to grade 8, whereas metric grades range from 8.8 to 12.9. from Frequently Asked Questions on Bolting Matters






then I realized they had stainless screws as well. why not baby my baby for a few dollars more?






however, after reading about it, it turns out stainless fasteners aren't as strong as the strongest steel fasteners (mostly because they are low carbon so they can't be heat treated as effectively?).

so then I started searching online for hex screws, and I stumbled upon this:





score! the size I need in 12.9 strength, at $0.30 a piece!

I only need 6 of them, so if anyone else is planning on having their crank pulley off in the near future, PM me and I'll ship some to you.

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OM617 in a 67 chevy pickup http://tinyurl.com/projectgmbenz