- Apr 8, 2022
Where did you find the 12 ft lbs max for torque on the head bolts? I found a chart here ( https://www.fastenermart.com/files/metric_tighten_torques.pdf) confirming your 17 ft lbs limit for grade 8.8 M8x1.25.The Studs & Nuts should be Metric Grade 8.8
Metric Grade 8.8 M8x1.25 bolts max torque is 17 ft lbs but obviously only torque your head bolts to 12 ft lbs
You would be surprised how little bit 12 ft lbs by hand can feel
Buy yourself an Inch lb Torque Wrench to be sure
Ft lb Torque wrenches aren't very accurate under 20 ft lbs
That's probably why most Inch lb torque wrench only go up to 240 inch lbs
Its tricky though finding M8x1.25 acorns, many dont have a grade at all, the one that did so far was grade 4.8 - ill keep searching.
Update: Pretty much all the acorn nuts are A2/18-8 (308) Stainless Steel. M8x1.25 = 5/16-18 bolt size. This chart (https://www.raajsagarsteels.com/fasteners_nut_bolts_screws_washer_studs/alloy_20_studs.html) says max torque is 132 inch-lbs (11 ft-lbs), so im guessing 18-8 Stainless Steel wont work?