head torque

[jdbubb at verizon.net (Dan Bubb)]

Gee, last time I torqued head bolts, I got the distinct impression that the torque required to turn the bolt that 1/2 turn very much leveled off.
i.e. the bolt was in the plastic region and was stretching.
150lb-ft?? Definitely not that high!

Mark, if I was you I'd call ARP even though the other Mark's data looks like it.

I have a torque meter. Next time I tighten head bolts I'll use it and see what the actual torque is. Obviously it'll vary due to friction variations which is why they went to the low torque, 1/2 turn approach, but it'll at least establish a ball park.

Forgot to mention the possibility of thread pitch affecting torque vs. clamping force.
Dan
  ----- Original Message ----- 
  From: LEF 
  To: Dan Bubb ; Mark F. ; Mtl-Marc 
  Cc: scirocco-l@scirocco.org 
  Sent: Sunday, July 30, 2006 11:34 AM
  Subject: Re: head torque


  Consider this:

   The Bentley for the '85 - '93 engine calls for tightening the bolts to 43ft/lbs, then adding another 1/2 turn.

  Now, as one who has tightened enough JP and JH head bolts over the last five years, I can tell you that the effort to reach that final 1/2 turn is 3-4 times what it was to achieve 43ft/lbs. ;)
    My calibrated arm says it's close to 150ft/lbs.

  54ft/lbs (or even 61), is about another 1/32 turn beyond 43ft/lbs.  

  larry
  sandiego16v


    In the days before the low torque then tighten a specific angle, VW head 
    torque is 54 ft-lb, 61 for a diesel.
    This is straight from the 1977 VW repair manual.


    I hope you are not assuming that the final torque setting for a head 
    bolt/stud is 65ft/lbs.  !!!

    larry
    sandiego16v