11/21/02
Because Torque can be different with different types of material. Oil alone
in the hole would change the TQ spec.
Ford is looking for a certain amount of Clamping force not TQ on the bolts. The
spec from memory is 28 ft lbs + a 1/4 turn.
Hammy, you're the engineer explain this better for me. I never explain stuff the
right way..
One other thing, $260.00 in parts is CHEAP unless you want to buy a $5000 motor.
Or to save the same motor from certain fate if done incorrectly. Mine will be
done (the one I’m selling) to Fords specs with all new Ford parts as required
then I will weld the cams. The next person that buys this car will have it for a
long time providing the tranny don't kill its self. I want the SHO to live
forever!.
That way Don has something to do :)
First off, all torque specs are dry unless otherwise stated.
We generally utilize 3 different types of torque specs at work.
Dry; no lubricants
Wet; petroleum based lubricants
AS; antisieze lubricants such as teflon, copper, moly, graphite, gold, silver,
white lead, etc based.
All very different torque values to attain the same force. Reason being that
lubricants reduce the friction, making it easier to "drive" the
fastener in thereby increasing the tension more than what was intended. Then as
well the torque values have to be mat'l specific to be accurate wrt transferring
force. e.g. A brass bolt and a S.S. bolt of the same size and class will deliver
a different force spec when torqued to the same value in identical scenario's
due to stretching and twisting.
Even then torquing is a crap shoot due to variables between holes, mat'l and
dimensional interface of the threads. For critical dimensions we use bolts that
are hollow from the head down almost through. We measure the stud length as is
from head to bottom of hole, and then keep measuring at intervals during
tightening to attain a pre-determined stretch of the bolt using depth mics. This
is the most accurate method. We also use x-ray and ultrasound as well to
determine stretch.
Having said all that I did a search and this says it better than my mind coming
off nights. It's short but to the point, applicable to all of us. And don't
forget to "warm up" the torque wrench prior to using, especially on
low range torques.
http://www.arp-bolts.com/pages/tech/fastener.html
John Hamilton (Hammy)
Ptbo, ON, CAN.
97 ES 105k km 91 Mocha/Mocha 150k km
Turbos Stock
Yoko db's