Steve did a NICE write up on how to properly install studs.
Some further details beginning with *
fiatfactory, post: 286278
If you wind them in tight, then undue stresses are placed on the top thread (where the stud screws into the block) and creates a possible failure point...actual torque is applied at the other end, bolt to stud. If you want to mount the studs more permanently then you can loctite them into the block so they don't unwind.
*Improperly installed studs WILL cause at the least a problem to a serious and fatal threaded joint-part failure.
Correct method for stud installation.
1. Clean the threaded holes in the block with a M10/M12 x 1.25 tap (or preferably a thread chaser)
*Taps used for cleaning out threaded holes should be chosen carefully as proper machine tool world taps are very different than the stuff found at the local hardware store, Horrid Freight and similar thread cutting tools. Proper taps are precision ground from High Speed tool steel, powdered metal technology, solid carbide and brazed insert carbide. There are high quality carbon steel ground thread taps that work well.
Proper machinery taps are graded and made for a specified thread fit per ISO specifications. The fit class designator for "normal clearance" can be 4G, 5G, 6H. Beyond this there is more and less thread fit clearances depending on host part design needs.
https://www.sandvik.coromant.com/en-gb/knowledge/threading/tapping/choice_of_tools/thread_tolerance_class
*Use a bottoming tap if possible to reach the bottom threads of an internally threaded hole. Most common tap is a Plug or taper tap which is designed to produce new threaded in a drilled hole. The Bottoming tap is designed to reach the last few threads of a threaded blind hole.
and rinse them clean with A GOOD SOLVENT, I use Isopropyl alcohol. (this makes fantastic engine final assembly cleaner) Isopropyl alcohol dries 100% RESIDUE FREE so will not affect the bond strength of the Loctite. (Solvents like brake cleaner, petrol and even acetone will leave a residue that does.)
*Alternatives to Iso Alcohol, Acetone, Brake Cleaner (pricy), Loctite Primer (very pricy). Solvent purity matters, common grades of solvents can have all sorts of impurities that will leave a residue causing other problems. There are Reagent Grade, Electronics Grade and other grades of industrial-lab solvents that have certified purity. The local lab supply house like
https://us.vwr.com/store/
will have this stuff.
*Ideally if the internally threaded hole to be cleaned should filled with cleaning solvent. allowed to soak, they flipped upside down to drain, rinse and repeat then blow dry with clean compressed air. Hint, lower air pressure works fine for cleaning out blind internally threaded holes.
2. Clean the threaded end of the stud going into the block with isopropyl.
*Same as above applies to the stud. Know ARP studs are shipped with a thick petro based anticorrosion protective coating, this MUST be removed before installation.
3. Test fit the stud into the internal threads of the block. They must fit and rotate smoothly with uniform friction during this test fit.
4. Remove the stud from the internal threaded block hole.
5. Apply Red Loctite (# 262 or #271) on the threaded end of the stud.
*Using high strength loctite Red or Green Loctite RC609 retaining compound is the way to prevent those studs from working loose under the most stressful conditions.
*The Loctite-ing the studs into the block prevents the studs from coming loose. What should never be done is over tightening the studs into the internally threaded holes in the block. This will cause the junction between the threaded and non-threaded area of the stud to crash into the entrance of the internally threaded hole, resulting in a threaded joint failure or at the least damaged threads.
^Historically in the US machinery world a class 5 interference stud to threaded hole was implemented between threaded hole and stud as the method of retention. This can be done when the design of the parts involved are to be jointed using studs. Since some of the original internally threaded holes in the Fiat block were not specifically designed and produced for studs. This procedure of using Loctite to secure the stud into a threaded hole is mandatory or there will be loose studs when they should stay put.
6. Assemble the threaded stud into the block.. hand tighten, not more than 4 INCH POUNDS.
*This is REALLY important. The common practice when installing studs is to crank them in as tight as possible into the threaded hole. This almost assures crashing the unthreaded area of the stud into the threaded hole entry. This WILL cause cracks and induce a LOT of stress on to that area of the threaded hole and stud producing a high risk of joint failure.
*The other way over tightening a stud into a blind hole causes problems is crashing the end of the stud threads into the bottom of the blind internally threaded hole. Once this happens, the threaded joint is under a LOT of stress, now add more stress by the remainder of the assembly process is a recipe for failure.
*Examples in this .pdf:
http://hhh.gavilan.edu/hspenner/iLe...rocessHardware/InterferenceFitStudsClass5.pdf
7. Apply some nickel (or silver) based anti-seize sparingly on the entire length of the UN-threaded area of the stud. This will help reduce the corrosion between the cylinder head and stud.
*This helps to prevent the dreaded cylinder head stuck on the studs syndrome. Between electrolytic corrosion, casting porosity and more adding a layer anti-seize or corrosion inhibitor like
https://www.vannay.com
to the entire length of the stud can make a very significant different when the cylinder head or stud jointed part is disassembled.
Previously discussed:
https://www.vannay.com/index.php?m=4&s=7
8. Apply the same anti-size or assembly lube on the remaining threaded end of the stud where the cylinder head nut goes. Different lubricants or no lubricant has a very significant effect on the clamp load produced with a given torque setting.
Here is that video again illustrating
Torque isn't Tension
9. Fit the cylinder head with a cheap disposable head gasket (I have a guarnitauto gasket that I use over and over again for this, I would never use this brand for final assembly) and torque the nuts in sequence to about 40lb/ft. Let sit for a few hours so the Loctite can set. This step ensures the newly fitted studs are completely square to the head surfaces while the Loctite sets.
*Loctite is an "anaerobic adhesive" or to cure-bond the adhesive the air must be removed. This requires applying enough tension into the threaded joint to drive out any air between the threaded surfaces. If this is not done, the risk of a loose stud during final parts assembly is high.
10. Remove the head again and remove the gasket and hang it up for next time... the studs should now be firmly in place and sitting exactly perpendicular to the block face.
11. go about with final assembly when the time is right.
This same method would also be used to set main cap studs into the block.
ARP also recommends applying tension / release several times before final torquing, for all studs / bolts (including their rod bolts when tightened with a torque wrench), The 'friction factor' changes from one cycle to the next. That is, friction is at its highest value when the fastener is first tightened. Each subsequent time the fastener is torqued and loosened, the amount of friction lessens. Eventually the friction levels out and becomes fairly consistent for all following repetitions. This phenomenon is known as preload scatter or preload error. This is basically the difference between the amount of preload achieved on the first installation of the fastener and the amount of preload achieved on subsequent torque/loosen/re-torque cycles.
*Do follow these ARP recommendations.
** Note on torque wrenches, the precision flat beam torque wrenches are the most accurate rugged-durable for a shop environment. The least accurate are the common micrometer clicker torque wrenches. These can go out of cal easy due to pushing beyond the click and the spring can changing spring designed in spring force if stored at a higher than lowest setting of the torque wrench. There is also a common practice of pushing the clicker torque wrench to click several times to "assure" proper torque. This often results in applying more torque to the joint than set on the torque wrench due to what is effectively an impact wrench effect. If the user is not careful with a clicker torque wrench, over torquing a fastener past it's stretch or yield point can and does happen resulting in significant grief. Using a precision flat beam torque wrench goes a long ways to preventing both of these common problems from occurring by allowing the user to "feel" the amount of torque applied and stopping if the fastener begins to feel soft (up to and past the material yield point) possibly preventing the dreaded broken fastener while being "torqued" syndrome.
*Best of the clicker torque wrenches are made by Stahlwille or Precision Instrument's or similar split beam clicker.
SteveC
*Bernice
