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6M torque specs question?????

3161 Views 12 Replies 7 Participants Last post by  SupraFiend
I'm rebuilding my 6M and understand the differences that the 6M brings to the rest of the motor, but my question is what torque specs should I use when putting it back together?

Options are:

A.) Since it's a 7M crank and rods, should I use the torque specs for the 7M when putting the mains and rods together?

B.) Do I use the 5M specs which are all a bit lighter?

C.) Should I just close my eyes and reef on it till my "f'd up wrist from hockey" gives out?

Much appreciated..

As a side note, I'm letting my 11 year old son pick out the paint colors for the motor. this could be interesting and I'll be sure to put up some pics. I'm psyched he'll come out and help me with this so it's a damn good trade off.

Here is a "before" picture:

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I'm planning on using the head bolts that were born with it. I can't come up with any real good reason to get aftermarket studs or bolts. Bolts certainly can't be the weak link in the head.
I was thinking the same thing. The bolts must be able to handle more than 58ft/lbs torque.

Time for me to geek out a bit:

Reason being, the head bolts are socket head cap screws. These types of bolts are "usually" aircraft grade. Similar to a SAE grade eight bolts.

That means a bolt that's 1/2"x20 SHCS can handle around 126 ft/lbs. I know this isn't the size of our head bolts, but it must be close.

I think the head bolts are 12mm, so here is some torque specs:

Bolt size Low Grade Grade 8.8 Grade 10.9 Grade 12.9
12mm 39 59 83 100

As long as the bolt grade is above grade 8.8 were ok. Since it's a SHCS, my guess would be it is way above grade 8.8
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I think that the newer style head bolts are more of the "torque to stretch limit" head bolts. I was under the impression that the older cars never used these. That's part of my reasoning for re-using the head bolts.

I'm not trying to be a cheap ass. It's costing plenty to rebuild this thing, but I don't want to put on head studs just to make it look pretty either. I want it to make sense.

Let me know if anyone knows if Toyota was using the "stretch" head bolts for these motors.

Weather we come up with the right or wrong answer, I think this thread has some good info and I appreciate it.
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