02-25-2016, 10:57 AM
Been there done that 
I torqued to spec on cold assembly and started driving around. I kept thinking I have to re-torque but never actually did it, thinking that at the 1000km service I'll do all the bits, head, rockers, oil etc. etc. So at 950km, coming off the highway at the off ramp, high heat, it blew out between 2 & 3. Lucky for me no water in this area. On replacement of the gasket, now paranoid, I used Spanjaard copper gasket spray, torqued, drove around the block, torqued, drove a little further torqued until there was no more movement in the nuts. The first hot torque was about a quarter turn.
I believe, apart from not re-torqueing early on, that my nuts may have bottomed out on the stud threads originally since the head is not what it was and the studs stick out further than other motors I looked at, so I put an additional hardened HV washer as well. If its a 11 stud head the stud next to the thermostat should also be torqued to half value as there is not much block in that area and there is a danger of breaking out the bottom end of the stud. (that said on the first attempt it was full torque and ok)
So far so good 3900km later, but I'll check them again at the 5000km service next week or so.
Also be aware that stray oil etc. on the threads affects the stud stretch and you may not be developing the clamping force you think, and torque wrenches should be calibrated at least once so you know its working properly. I got mine in about 1980 when I built my first bike engine and was pleasantly surprised to find it still accurate within a couple of percent 30 years later!
I torqued to spec on cold assembly and started driving around. I kept thinking I have to re-torque but never actually did it, thinking that at the 1000km service I'll do all the bits, head, rockers, oil etc. etc. So at 950km, coming off the highway at the off ramp, high heat, it blew out between 2 & 3. Lucky for me no water in this area. On replacement of the gasket, now paranoid, I used Spanjaard copper gasket spray, torqued, drove around the block, torqued, drove a little further torqued until there was no more movement in the nuts. The first hot torque was about a quarter turn.
I believe, apart from not re-torqueing early on, that my nuts may have bottomed out on the stud threads originally since the head is not what it was and the studs stick out further than other motors I looked at, so I put an additional hardened HV washer as well. If its a 11 stud head the stud next to the thermostat should also be torqued to half value as there is not much block in that area and there is a danger of breaking out the bottom end of the stud. (that said on the first attempt it was full torque and ok)
So far so good 3900km later, but I'll check them again at the 5000km service next week or so.
Also be aware that stray oil etc. on the threads affects the stud stretch and you may not be developing the clamping force you think, and torque wrenches should be calibrated at least once so you know its working properly. I got mine in about 1980 when I built my first bike engine and was pleasantly surprised to find it still accurate within a couple of percent 30 years later!
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