head torque+rocker arm end play

[Rod Neff <rodneyneff@xxxxxxxxx>]

 Clive wrote
>>It is important to accurately establish the "starting" point of the 
90+90 angle torque with the initial 20Nm.<<
 
 I think this starting point is the root of the stripped head stud problem,
its rare but does happen. I have been to 2 different dealer to buy a head
stud for testing purposes, and neither had one in stock.

 Plotted out, the relationship between nut rotation and torque is not 
linear, for instance, just as an example, say a nut is at 10 ftlbs and you
turn it 30 degrees and thats put is it to 15 ftlbs, now with the nut at 30
ftlbs, turning it 30 degrees puts it at 60 ftlbs.

 Some testing on this.
http://www.pbase.com/image/41825708 

  I have only done rocker end play on 3 slightly used oil heads, which i
owned at one time, all had the 600 check up done at different local dealers,
i found the final torque and they were 34(95rs), 36(98gs), and
37(00gs)ftlbs..
 
 This is a very small test lot, but it tells me even the trusted
professionals have a 10% window.

  Why did i go with 400inch lbs.? about the middle of the page read what 
Hank writes,,
 http://www.advrider.com/forums/showthread.php?t=37535&highlight=300k 

 There is a final torque window, i am not sure what the extremes are, on 
the low end you need to keep from blowing head gaskets and stop weeping oil,
on the high end the weak link is apparently the engine case. 

 The 20nm then 90+90 system works good and stretches the bolt in the 
elastic range, it bypasses the many variables in regular torquing like a
burr on a thread or the amount and type of oil etc.. 

 But again, you have to have an accurate, calibrated torque wrench to
establish the starting point.

 Anyway this is a complex subject with many aspects, which i am no expert
at, or have alot of data on, however at regular job i am involved in bolt 
torque, but its in a structural sense, bridge/building etc. 

 Do what you think is best for you, but in conclusion, after you do your
90+90, set the wrench at 37ftlbs, if it clicks off easily you may or may 
not have a problem. on the low end try 33, if you are under this you may
want to double check your work.

 Rocker arm end play: i have large C clamps, same ones i used to use on the
airheads, after doing several different experiments, i found the easiest way
for me to set rocker arm end play was to just barely clamp end play to
.000", torque to 10 ftlbs, then remove clamps, then final torque,,, during
the final torque the end play spreads out to 3 to 5 thousands, without
looking i think the spec is something like 2 to 15 thousands, most of mine
were between 8 and 16 after the 600mi service,, noise wise, in my opinion,
is not as critical on the oilhead compared to an airhead.

 rod neff
 santa monica
 98gs
Take Yahoo! Mail with you! Check email on your mobile phone. 
http://mobile.yahoo.com/learn/mail 

------------------------------

End of oilheads-digest V2 #86
*****************************