Oh Magoo (Randy) You've done it again.
08-29-2008, 12:20 PM
#31
Captain Obvious
Super User
Super User
I owned a Laverda Jota motorcycle; quite rare Italian beaut............it had studs that screwed into the crankcase, the barrels then slid over these studs then the head all secured by nuts that were tightened in sequence at 3 different torque values. When first inserting the studs into the crankcase (read block) you had to 'double nut' at the head end and apply loctite to the block end. Then you had to ensure all the stud heads were on even plane minimising head distortion when tightening it all down. Given that the 928 studs are 'only' holding the head down the same principles should apply.
BTW.............is it Llamas your after AO or Luppins...............perhaps 2 different MP sketches
BTW.............is it Llamas your after AO or Luppins...............perhaps 2 different MP sketches
I’m working on a project car to generate some revenue to pump it back into the 928 and it also has a 3 step toque procedure to tighten the head down. It has bolts, not studs but that really doesn’t matter. What’s interesting is that this in just a plain old 2.0L Mazda engine. So the torque angle technique is getting more wide spread than before. The head bolts in this engine are supped to be one use only and you can actually fell them stretching when the last 90 turn is applied.
08-29-2008, 08:23 PM
#32
Nordschleife Master
Join Date: Dec 2004
Location: Guelph, Ontario, Canada
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The fact is the bolts, studs, whatever stretch at a very repeatable amount along the axis for a given amount of motion.
The amount of force that you put on the stud in rotation varies EXTREMELY with the amount of and type of lubricant that is on there as well as the surface finish of the thread faces.
At low torque these numbers are very close and separate and become larger as the amount of torque increases.
There fore ALL motor manufacture's that I have delt with (Ford GM Chrysler Toyota) use the torque to a low value (always the same no matter what the condition) then use angle of rotation to stretch the bolt or stud a predetermined amount. This results in a much better determination of the amount of force on the stud so that it is in elastic deformation and does not transfer over to plastic deformation.
and yes I stayed in a lot of Holiday inns as I worked in these engine plants installing gauges.
The amount of force that you put on the stud in rotation varies EXTREMELY with the amount of and type of lubricant that is on there as well as the surface finish of the thread faces.
At low torque these numbers are very close and separate and become larger as the amount of torque increases.
There fore ALL motor manufacture's that I have delt with (Ford GM Chrysler Toyota) use the torque to a low value (always the same no matter what the condition) then use angle of rotation to stretch the bolt or stud a predetermined amount. This results in a much better determination of the amount of force on the stud so that it is in elastic deformation and does not transfer over to plastic deformation.
and yes I stayed in a lot of Holiday inns as I worked in these engine plants installing gauges.
08-29-2008, 09:23 PM
#33
Rennlist Member
Laverda were a company thats was spawned from the ag. industry in Northern Italy close to where Ducati has there company. My bike was the 1000cc 3cyl model so each cyl. was 333cc @ 11:1 comp.
The 5.0l 928 motors are 625cc per cyl. at lesser comp with shorter studs and a lower rev. range should be more than fine with the aforementioned torque sequence IMHO.
