You have several options:
- The internet is a vast resource ... use your Google-Fu and figure it out. You can always ask on here. There are enough of us on here we can get you the torque value for your fastener.
- You can use the following torque chart from the Bolt Depot:
- If all else fails, get a dial indicated torque wrench. Put it on the fastener and turn the handle until you just start to feel the fastener turn. Do this slowly and pay attention to where this happens. Round it to the nearest 5lb-ft and you should be right there. I know this is basically reverse engineering the torque, but it should put you in the right range of torque.
While torque specs are very important, what is more important is getting the torque specs even between fasteners, especially with things like head bolts.
Another thing to be aware of when torquing bolts is to figure out whether the bolt is torque-to-yield (T2Y). These fasteners are one use only and must be replaced once taken apart. These fasteners will also most likely have the final torque sequence which works from the stretch of the both and not from the torque itself. The final sequence is done by turning the fastener a certain amount of degrees. A torque sequence may look like:
- First: 20 lb-ft
- Second: 40 lb-ft
- Third: 60 degrees
(NOTE: These are just numbers I've thrown out there for understanding.)
You cannot tell by the way a bolt looks as to whether it is a T2Y bolt or a regular one ... you have to look up the spec. If you don't know and don't do it right, you'll most likely blow a head gasket. This is very important.