Need bolt experts advise here

[my1stgn]

So Im putting the Valve body back on the trans and I end up snapping a bolt. The bolt is a M6x1x45mm bolt. According to the CK Performance book , this bolt should be torqued down to 140 inch lbs. Now if Im not mistaken, 12 inch pounds is equal to 1 ft lb correct?

So I go over to Napa and look at there bolts. My bolt says TR 10.9 on the head. Napa's bolt says W.T 8.8 on the head. So I ask the lady " Hey dont you have some stornger bolts like grade 8 stuff?" She tells me this is better than grade 8. Im like my bolt says 10.9 on it, wouldnt a 8.8 bolt be weaker. Shes says no, so me as a dumbass (Im ASE Master Cert., she's aprobly a High School Grad..... like 30 years ago) think, hey maybe this lady knows more than me. I get home and dont even think about putting them in until I look up some info. Turns out 8.8 grade bolts (metric) are weaker than 10.9 grade bolts which are weaker than 12.9 bolts. So now Im looking to order some from this website I find and look further and then another question pops up.

Is the CK Performance manual wrong? According to the link below, 10.9 bolts are good to 10 ft lbs. Using my calculation of 10 ft lbs = 120 inch lbs (1 ft lb= 12 inch lbs) would I just keep braking the bolts if I keep torquing down to 140 in lbs? The first one I torqued down would not stop at 120 inch lbs, it would keep twisting and twisting and I knw it was gonna break. So I did the second one and it kept twisting and twising till about 130in lb when it broke.

US & Metric Bolt Torque by Grade

So my question is :

1) Am I correct by saying 10.9 metric bolts are stronger than 8.8 bolts?

2) What is the torque spec for the valve body bolts?

thanks again fellas!

 

[my1stgn]

 

[Lee Thompson]

I use

90 in. lbs.

 

[87LtdT]

Your calculations are correct...1 ftlb = 12 inlb.

Grade 12.9 are stronger than 10.9 which are stronger than 8.8...etc...just like Grade 8 SAE are stronger than Grade 5, etc. Think of this when you see no grade marking on the bolts of your Chinese made engine stand!!! Generally, Grade 10.9 are considered approximately equivelant in strength to SAE Grade 8, and Grade 12.9 are about 15-20% stonger than Grade 8..

I do not know the torque spec.

When tightening capscrews you should also consider if oiled, dry, dirty, etc. If oiled, the recommended "dry" torque value should be lessened a bit because the oilier capscrew will turn easier than the dry one and stretch further (which might yield the capscrew) with the same amount of torque... For example, I believe the ARP head bolts have different torque specs if oiled, or if the ARP lubricant is used.

A link with some info:
Keeping It All Together, Part 1

Regards, Bob

 

[Project TNX]

I would PM Brian Hofer, he knows these tranny's like the back of his hand.

 

[Lee Thompson]

you will be fine

With 90 in. lbs.--Go to 100 if it makes you feel better.

 

[my1stgn]

With 90 in. lbs.--Go to 100 if it makes you feel better.

The funny thing is I had torqued all the bolts to 100 in lbs before I went to 140 in lbs and thats when 1 bolt stretched out (so I stopped short at like 130 inch lbs) and then the next one snapped. Should have went with my gut and left them at 100in lbs. Oh well, live and learn!