Bolt torque discussion

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Duane

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I started this thread for anyone who wants to discuss bolt theory
Or torque on the sbm.
What do you torque your bolts or studs to and why.
 
Except for the misprints such as rocker shaft bolts I torque mine to whatever the shop manual says, unless using some aftermarket setup that says otherwise. Why is this a mystery? You can look up standardized fasteners, grade 5, grade 8, etc, and all of that info is published.
 
Except for the misprints such as rocker shaft bolts I torque mine to whatever the shop manual says, unless using some aftermarket setup that says otherwise. Why is this a mystery? You can look up standardized fasteners, grade 5, grade 8, etc, and all of that info is published.
Thanks for the reply. I posted this thread as a carryover from another thread where there was indeed plenty of disagreements on the torque when using studs.
Rather than hijack the other threads and out of courtesy I started this thread. Eg arp recommends a stud torque of 140 lbs with oil for 1/2 inch studs 45 lbs higher than stock.
 
I had a good link saved amongst my 100’s on bolts but couldn’t find it tonight. I will dig again tomorrow if I get a chance
 
I started this thread for anyone who wants to discuss bolt theory
Or torque on the sbm.
What do you torque your bolts or studs to and why.
I have read on this forum that some guys torque the longer head bolt studs to a higher torque than the shorter ones to get the longer bolts properly tensioned.
Another guy questioned whether the block itself would be damaged by this increase over stock to the block.
 
A lot of time if we stop and think about what we are torquing against it makes you rethink things. I totally screwed up a set of W2, 300 plus cfm heads by going by the book. They are wall learners in my shop that I can’t bring myself to scrap yet. I ran 9.80’s with them on BP93 pump gas.
 
A lot of time if we stop and think about what we are torquing against it makes you rethink things. I totally screwed up a set of W2, 300 plus cfm heads by going by the book. They are wall learners in my shop that I can’t bring myself to scrap yet. I ran 9.80’s with them on BP93 pump gas.
Can you elaborate, you said they cracked?
 
Before I call it a night for the go by the book guys proper torque to yield puts x amount of stretch on each bolt. Sooner or later the elasticity of that bolt is lost. How do you know when this occurred unless you Mic each bolt and mark each one for size. Some of my studs are over 30 years old so just something to think about
 
Before I call it a night for the go by the book guys proper torque to yield puts x amount of stretch on each bolt. Sooner or later the elasticity of that bolt is lost. How do you know when this occurred unless you Mic each bolt and mark each one for size. Some of my studs are over 30 years old so just something to think about
I do this with rod bolts
 
I use whatever manufacturer specs who made the bolts or studs. If using stock stuff, I go with the factory specs. ARP for instances gives specs for their bolts and studs. If I use ARP I use their specs. Kinds simple, really.
 
I use whatever manufacturer specs who made the bolts or studs. If using stock stuff, I go with the factory specs. ARP for instances gives specs for their bolts and studs. If I use ARP I use their specs. Kinds simple, really.


I was minus 10 pounds on my W2 heads and they cracked. Calibrated digital snapon torque wrench. I just read today about a guy cracking a set of 360-1 heads. Hmmmm
 
To spec., because there's a specification for a reason. Once in a while you have to go by feel because a torque wrench simply won't access the bolt or nut, but if you've been doing this (working on cars) long enough you develop a feel for torque. In fact the last aftermarket intake I did, I didn't use a torque wrench at all, I followed the torque pattern of course, but went with "snugged the f**k down" as my spec. :thumbsup:
 
To spec., because there's a specification for a reason. Once in a while you have to go by feel because a torque wrench simply won't access the bolt or nut, but if you've been doing this (working on cars) long enough you develop a feel for torque. In fact the last aftermarket intake I did, I didn't use a torque wrench at all, I followed the torque pattern of course, but went with "snugged the f**k down" as my spec. :thumbsup:
I worked with a guy who would use a standard pull bar and make the "click click" torque wrench noise with tongue to roof of mouth. Of course that was just in assembly. He would come back with torque wrench for final torque. He got lots of strange expressions and/or laughs though.
I can imagine the torque spec of aftermarket male stud or bolt exceeding the strength of the female threads ( 50 yr old cast iron ) its into. Good luck to all
 
I have read on this forum that some guys torque the longer head bolt studs to a higher torque than the shorter ones to get the longer bolts properly tensioned.
Another guy questioned whether the block itself would be damaged by this increase over stock to the block.
Interesting.... Just a wild guess on the thinking behind this, but it sounds like this particular concept of properly torqued is to try to achieve a set amount of stress in the bolt/stud. Are they looking at bolt stretch and trying to get the stretch to be in proportion to the length, or ????
 
Interesting.... Just a wild guess on the thinking behind this, but it sounds like this particular concept of properly torqued is to try to achieve a set amount of stress in the bolt/stud. Are they looking at bolt stretch and trying to get the stretch to be in proportion to the length, or ????
Well theoretically all recommended torque spec are based on the optimum stretch for the material, but as I understood it the longer a fastener, is it would need slightly more torque to be optimum.
 
To spec., because there's a specification for a reason. Once in a while you have to go by feel because a torque wrench simply won't access the bolt or nut, but if you've been doing this (working on cars) long enough you develop a feel for torque. In fact the last aftermarket intake I did, I didn't use a torque wrench at all, I followed the torque pattern of course, but went with "snugged the f**k down" as my spec. :thumbsup:
I agree, but some fasteners are more critical than others.
I will not use a torque wrench on rod bolts anymore. Stretch gauge only because they have to be right.
My eagle rods with 7/16 cap screw bolts take an insane amount of torque(86ft lb) to get to the recommended arp stretch.
By feel I would not be even close.
 
I use whatever manufacturer specs who made the bolts or studs. If using stock stuff, I go with the factory specs. ARP for instances gives specs for their bolts and studs. If I use ARP I use their specs. Kinds simple, really.
I ordered a custom set of studs to fasten my front motor plate to the front of the timing cover.
The long 4 bolts go into the block,2 go into the aluminum thread cover, no recommendations from arp as this is custom.
What would you torque these studs to and would you torque the ones threading into the aluminum the same?
 
I watch some guys doing head bolts, main bolts, and head bolts not lubing the washer and bottom of the nut where it’s probably most important. When I torqued my aluminum rods in my 572 I called the and they gave me a number. I was told to slightly snug the bolts and go to full torque on one pull and move to the other side. That was different.
 
Bolts/studs are to be thought of as really stiff springs. You want to stretch them within the bolt/stud's elastic range. That is to say, so it will return to the unstretched length when loosened. This is the most accurate way to tighten a bolt. Next best is with a torque wrench. The torque wrench with a beam is the most accurate over time. I won't have a clicker.
 
Well theoretically all recommended torque spec are based on the optimum stretch for the material, but as I understood it the longer a fastener, is it would need slightly more torque to be optimum.
I wouldn't think a longer fastener would always need a little more torque. I can see where the thinking comes from.
With US Standard thread form, the load on all of the threads is not even. The threads nearest the end are doing most of the work (see the mst elastic deformation). So on a really long bolt, there could be torsional twisting between the threads at the end and the toirque wrench. How much would depend on the diameter, the length, the material and the form (AN, USS, SAE etc).
Metric thread forms has the same characteristic, some argue worse.
 
Clearly one disparity is the generalized torque specs are based on an assumption about what is being threaded.
Threading into a casting, I've got to think the cast material and shape is going to be a big factor.
 
I watch some guys doing head bolts, main bolts, and head bolts not lubing the washer and bottom of the nut where it’s probably most important. When I torqued my aluminum rods in my 572 I called the and they gave me a number. I was told to slightly snug the bolts and go to full torque on one pull and move to the other side. That was different.
Or the guys that dip the bolts in oil and stuff them in the caps. Oops!
 
Clean the bolt holes with rethreaders. Not taps! Rethreaders are bottoming by design and will clean the threads and won't remove metal. Blow all the bolt holes out clean and dry.
 
Off topic but I watch guys use locktite on bolts (often convertor bolts) and not remove the old locktite or clean the oil from them and then complain about locktite not working. Bolts must be cleaned.
 
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