Type Three Tuning Page -- Cylinder Head

Please select the area of interest:

Just to clarify something...

Because the factory torque spec for an 8mm stud is 18 ft-lb and for a 10mm
stud is 23 ft-lb, many people draw the incorrect conclusion that the 10mm
ones have a higher preload.  They think that the 8mm ones are too weak to
hold.  This is absolutely false - they get the SAME preload!

What they don't realize is that the emperical approximation to relate
tightening torque (i.e. how hard you are twisting the wrench) to actual
preload (i.e. how hard the stud is holding the things together) is:
Torque = PreloadForce x ThreadDiameter x Coefficient

While determining the exact coefficient is a rather difficult task (it
depends on everything!), it doesn't take too much effort to understand a
general trend here: the bigger the bolt, the more torque needed to get the
same preload.

And, look at this:
23 ft-lb * (8mm / 10mm) = 18.4 ft-lb.

VW specified *approximately* the SAME preload for both kinds of head studs!

Take care,
Shad Laws
LN Engineering - Aircooled Precision Performance
http://www.lnengineering.com

While the engine is on #1, you can check both #1 valves, the intake on
#2 and the exhaust valve on #4. Now turn the engine over 360 degrees and
check the valves on #3 and the intake on #4, and the exhaust on #2.

...Also, the factory had star washers under the heads of the
bolts originally. Some silicone gasket adhesive over the heads of them
after ther are tight will keep them from backing out. 
Don't forget to put the thermostat bell crank under the 2 top center
head bolts, if your engine had them originally. Stuff rags in the intake
ports until you are ready to install the manifolds...

-- 
russw @ www.classicvw.org