I don't care for any auto part that is throw away after a single usage. The damn things are prone to breakage when being removed which creates more problems.
 IMO, could be wrong but TTY was created by the auto industry to reduce the amount of metal used in making hardware.

Last edited by Rudi (2/14/2016 11:41 AM)

TTY bolts are junk.  They are absolutely 100% designed for ease of installation on an assembly line because they do not require accurate torque calibrations for their installation.  Think of it this way, a TTY bolt is in effect already failed.  You torque the bolt to the point where it becomes permanently deformed, which is why these bolts are one time use.  A regular bolt is torqued until it is stretched, but still within the limits of plastic deformation, meaning that the bolt becomes in essence a spring.  It holds its load under tension, but when tension is released it springs back to its original shape without permanent damage.  Now, there's a limit to this, due to the fatigue life of the material from which the bolt is made, which is why I would not reuse a regular head bolt more than about 3 times, but that's not the whole story.

The real issue is the idea of a TTY bolt being in essence already pushed past failure.  Without launching into a three page treatise on metallurgy here's the gist of it.  Steel at the molecular level is arranged like a lattice.  The lattice is strongest when it is uniform and undistorted.  Tempering steel actually improves the lattice structure by opening the lattice under heat, allowing carbon atoms to migrate into the lattice, and then constricting the lattice around them under cooling.  This creates a more uniform distribution of carbon, and a more stable structure.  When you permanently deform a piece of steel it rends the lattice and actually starts to cut tracks through it.  This both weakens the structure, and those tracks make it easier for the metal to undergo further deformation with less effort than the yield strength of the material, because the yield threshold has already been breached.  So the TTY bolt is both weaker and more prone to failure than its regular brother.

Now, in an engine where there are a lot of head bolts this isn't that big a deal because like rivets in an airplane the strength lies not on any one fastener, but on the overall strength of the assembly.  But when you get into engine designs like the SBF, LS1, or my personal favorite (and why I know so much about this) the Ford/IH 6.0 Diesel each fastener becomes critical when there are only say 10 bolts holding each head to the block.  In these instances the TTY bolts are basically a time bomb, especially when you add forced induction into the mix.  In such instances the best course to ensure longevity and prevent head gasket issues is to install studs and sometimes cut o-ring grooves into the cylinder head deck and/or block deck.  The studs produce a much greater clamp load than even regular bolts could.  The o-rings preload the seal around the cylinders to prevent combustion pressure from leaking outward.

So, in a nutshell I would avoid TTY bolts for critical jobs. 

ARP...torque em down and forget about them...reusable too....jj

I promise I'm not trying to be argumentative, but that's simply not correct.  A TTY bolt is not relying on the elasticity of the bolt material.  A TTY bolt has been deformed past the point of elasticity, as its been permanently deformed.  Once that happens the modulus of elasticity no longer matters because you are now in the realm of yield strength.  A TTY bolt has been pushed to the point of yield and slightly beyond. 

If the issues you were having with HGs prior to the introduction of TTY bolts were HGs from the factory then the issue was the reason why they started using TTY bolts in the first place; the factory assembles engines too fast to constantly keep calibrating the machines used to torque the bolts.  In this instance TTY bolts offer superior repeatability and much more consistent results, which is why they are used. 

SBFs are usually not an issue until you run forced induction. 

Overhead cams with the cam lobes acting directly on buckets atop the valves.  If limited to a cam in the block arrangement, if there were no other concerns (cam lobes hitting the rods for example) you'd be best off running the lowest rocker arm ratio possible and doing it with the cam.  Higher ratio rocker arms can play havoc with valvetrain geometry and put more stress on components.  Really they are a crutch to get a little more cam without having to swap the cam.  I remember an Engine Masters Challenge winner from some years back that ran 1:3 ratio rockers citing less stress and thus more accurate cam timing.  But he was also running an engine where he had carte blanche to make internal modifications, so I'm not sure exactly how he did it without having anything hit.  This is more of an extreme example of what you could do, but not what most guys are going to do.  Point being, given the choice I'd run lower ratio rockers and the appropriate cam.

Why aluminum heads?  If anything aluminum heads move around more than iron and need a better clamp load to ensure proper head gasket sealing.  With aluminum heads I almost always use studs. 

The biggest issue with TTY bolts would be worse on aluminum heads.  Every material has a fatigue life.  Starting fresh a material has a certain yield strength, the amount of force required to achieve permanent deformation; the point after which it will not spring back to its original shape.  But, that's not the whole story.  Materials also have a fatigue life, which is the point at which they have endured so much plastic deformation (deformation from which they can spring back, below the yield threshold) that they become permanently deformed WITHOUT having ever been subjected to force in excess of the yield strength.  Think of it like a boxer.  Yield strength is the one punch knockout, fatigue life is when the cumulative effect of many blows causes the ref to end the fight.  The big problem with TTY bolts is that they have already been permanently deformed, which means that their yield threshold has been reduced, AND the fatigue life has also been reduced.  So now, not only will the bolt continue to deform from force below the material's yield strength, but also have a shorter cyclic life, because the fatigue life is also reduced.  Every time a cylinder fires force is applied to the fasteners holding the head to the block.  Think about how many times that happens per minute (125 times at 1,000RPM and 750 times at 6,000RPM just for points of comparison).  Every time it happens that's one cycle.  A fastener only has so many cycles before it stretches, and a TTY bolt has fewer cycles in it than a regular bolt, a stud has more than a bolt.  With aluminum heads the head gives less resistance, forcing the fasteners to take up the slack, putting more stress on them, and reducing the cyclic life.  So a TTY bolt with aluminum heads would to my thinking cause an already shorter lived fastener to live an even shorter life.