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By MarkMontereyBay - 14 Years Ago
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Harmonic Balancer crank bolt torque? My manual says 130 to 145 Ft pounds for a 312. I have it to 125 now. I don't like the way it feels. Feels like it will twist the bolt. Is this spec correct?
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By 46yblock - 14 Years Ago
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That sounds like more than enough Mark. I usually go for 95.
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By MarkMontereyBay - 14 Years Ago
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Mike,
I searched around the net and all results for 312's are 130-145. 292's and smaller are 80-95. I am using a Snap-On clicker torque wrench so it is fairly accurate. I am going to leave it where it is now unless someone here with more knowledge than I says go the rest of the way. Seems like overkill to me and stripped crank threads or a broken bolt in it is not a good thing.
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By PF Arcand - 14 Years Ago
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Mark: It seems odd that the 312 would have that much higher a torque figure than the 272-292s. Seems like it could be a similar situation to early 1956 312 main cap specs, which were way to high & led to disastrous cracked blocks! Hopefully an engine guru or two here may comment....
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By Ted - 14 Years Ago
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85-95 lbs. for the damper bolt torque is more than sufficient. Both the 292 and 312 engines use the same damper bolt so the torque is expected to be the same for both. That 130-145 number found in the footnotes in the ’57 service manual would appear to be just one more typo in that book to add to the list.
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By MarkMontereyBay - 14 Years Ago
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Thanks Ted, I will back it off and re-torque it this morning. Truly pissed off about the possibility of damaging the crank and glad I followed my gut checking in here. I searched the archives for something on this but didn't find it. Maybe I was entering the wrong search words.
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By PF Arcand - 14 Years Ago
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Mark: would be a good idea to put a line thru that spec in the manual, so that mistake won't happen again to u or someone else..
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By MarkMontereyBay - 14 Years Ago
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Paul,
I definitely won't repeat this error. I tend to remember stuff like this, even at my age. I did have some stronger plans for the 1957 Service Manual but have cooled off for now. I will obliterate the footnote for anyone who comes in contact after I am gone.
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By Jimz Bird - 14 Years Ago
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More torque clarification please.
Here is the chart from the 56 Shop Manual and again there are other variances in the torque values.
What should they really be for 272-292 and 312?
Thanks!
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By MarkMontereyBay - 14 Years Ago
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The chart is incorrect for damper torque. 312 inch engines are shown having a damper to crankshaft torque of 130-145 pounds. The correct 312 damper to crank torque is 85-95 pounds. I also wonder about the spec for the cam sprocket to cam bolt.
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By aussiebill - 14 Years Ago
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MarkMontereyBay (7/23/2011)
The chart is incorrect for damper torque. 312 inch engines are shown having a damper to crankshaft torque of 130-145 pounds. The correct 312 damper to crank torque is 85-95 pounds. I also wonder about the spec for the cam sprocket to cam bolt.Mark, i think the bolt torques you want to apply to these old bolts can lead to broken bolts in some cases, most bolts you get a feel for initial tightness then sneak a little more controlled tension by feel, thats all they need. this is referring to most external bolts, regards bill.
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