G Body Parts Body Bolt Kit

[pontiacgp]

So if I get the cheaper bolts, what toque spec am I using? And is it a lubed or dry spec?

dry toque is 52 ft lbs....if you want to lube the bolts then you need to lower the torque according the the lube you used. The reason for the torque is clamping and a lubricated shaft of the bolt does not bind like a dry bolt. calculated in when the give you the torque requirement. I torqued them dry with antiseize on the threads and torqued them to 52 ft lbs. The issue with antiseize if it affects torque is questionable by what I have read.

 

[joesregalproject]

Okay I'm going to get the 10.9 bolts and I'll put antiseize on them and torque them to 52 ft lbs. Thanks GP.

 

[pontiacgp]

and those are the correct bolts, not the cheaper ones. If you recall the A body Chevelle SS with their factory big block they used a grade 8 bolt for their body bolts which held those bodies on with all that power. The 10.9 is the metric equivalent to the grade 8 bolt

 

[joesregalproject]

and those are the correct bolts, not the cheaper ones. If you recall the A body Chevelle SS with their factory big block they used a grade 8 bolt for their body bolts which held those bodies on with all that power. The 10.9 is the metric equivalent to the grade 8 bolt

That's what I thought, but shouldn't there be more than 1.2 ft lbs of accommodation on the bolts? In other words, If I'm torquing them to 52 ft lbs and the max is 53.2 ft lbs, is 1.2 ft lbs enough leeway to make sure they aren't over torqued?

Either way, I already ordered the 10.9 bolts, but I am curious.

 

[pontiacgp]

The max torque is calculated 90% of the bolt's actual yield strength so you have more than 1.2, you'll have over 6 ft pounds above the 52 lbs before you hit the maximum. The other basis for which bolt to use is shear strengths. The grade 8 bolt used in the A bodies is identical in it's shear strength as the 10.9, no need the spend the extra money on overkill


SAE KSI Metric KSI
Grade 5 120 8.8 120
Grade 8 150 10.9 150
Grade 9 180 12.9 180

 

[joesregalproject]

The max torque is calculated 90% of the bolt's actual yield strength so you have more than 1.2, you'll have over 6 ft pounds above the 52 lbs before you hit the maximum. The other basis for which bolt to use is shear strengths. The grade 8 bolt used in the A bodies is identical in it's shear strength as the 10.9, no need the spend the extra money on overkill


SAE KSI Metric KSI
Grade 5 120 8.8 120
Grade 8 150 10.9 150
Grade 9 180 12.9 180

Okay, I see. Thanks GP, saved me a few bucks and taught me something.

 

[pontiacgp]

there is another aspect of torquing, if you are given a torque requirement for a nut with a bolt and you torque by the nut you use the torque value given, if you torque by the head you add 10% to the amount of torque applied. These body bolts are torqued by the head and the torque was calculated with that considered so if you were able to check the torque on the nut you would find it about 10% below the 52 ft lbs, you are actually well below the yield limit. If you wonder where I got this info from I worked building aircraft for more years that I will admit to and worked on test aircraft (CL 600) when they were going through tests for their FAA certification.