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#1
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Torque specs - wet vs. dry
A general question:
Just read an old article on torqueing fasteners correctly. Pontiac manual says final torque on heads should be 95 ft-lbs dry. Rotella book on rebuilding Pontiacs also says 95 but to lubricate threads and under head with 30W oil assuming use of original head bolts and studs. Based on article, using oil as lubricant reduces torque needed by as much as 25% - 40% depending on whats used. Anyone take into account lubricant when torqueing or do you just use manual Question is also applicable to pan bolts, timing chain cover, etc. |
#2
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Everything you stated is correct except possibly the 95 lbs. dry. Could you tell me exactly which service manual you saw that in? I have all the chassis manuals from 1958-1975 for Pontiac and I will look at them to verify for you. It would be unusual to state dry torque specs for assembling an engine, since it's naturally oily. Generally, when nothing is stated, the factory torque specs are for fasteners clean and lightly oiled on the threads and under head. The only common exception is for lug nuts. That is a dry torque spec for them. Also, when using aftermarket fasteners like ARP, use their torque specs and their lubricants, nothing else.
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#3
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1972 Pontiac Service manual states 95 lbs final torque
Good to know what is assumed when they give torque specs in the manual. Appreciate that info. Actually manual states "Cylinder head bolts should be installed without thread sealer of any kind" so I guess thats different. Agree on ARP comment. I was just referring to Pontiac factory hardware. |
#4
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"Dry" probably meant "moist but not puddled to cause hydro-lock". See ya gotta assure the holes are filled with oil.
let's use some sense here. Oh, I use grease on lug nuts. |
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#5
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To try and word the general question better....do you adjust torque specs based on what lubricant, if any, you use on thread bolts?
I never thought about this until reading an article recently that recommends a reduction in the torque based on the type of lube. Table attached. Given the table, I would assume its important to know what lubricant, if any, Pontiac assumed when providing their recommendation on bolts. |
#6
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Lube is definitely a factor with regard to applied torque. I work on aircraft and there is a separate spec for lubed vs dry. In the same vein, there are separate specs depending on if you are torquing the head or nut side on a through bolt. (Torquing the nut is preferred)
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67 LeMans, 326, M20, 3.31 12 Bolt |
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#7
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Thats interesting that there is difference depending on the bolt side or nut side. Never thought about that.
I was surprised by how much the adjustment is for a dry torque vs. one with ARP or even oil vs. ARP (see table from previous message) |
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