Where Are TTY Bolts Used?

In simple terms, you need torque to create tension in a bolt. You use torque to turn a nut onto a bolt and then to stretch the bolt, making it a solid spring that clamps the two materials together.

Why do manufacturers use torque to yield bolts?

Many vehicle manufacturers use torque to yield bolts; especially on engines with aluminum heads and or in conjunction with (MLS) head gaskets. Because, they provide more consistent clamping loads, across the entire head-to-block mating surface. … Reusing the old bolts, can cause expensive engine failure.

What happens if you reuse TTY head bolts?

Torque-to-yield (TTY) head bolts are designed to stretch when used. Once stretched, they are not as strong as before. Consequently, they cannot provide the same amount of clamping force and may break or shear off if reused.

Is it necessary to replace head bolts?

Bolts with any signs of damage, no matter how slight, should never be reused. Not only will the bolts eventually fail, but when they do, there is the potential for them to cause damage to your cylinder head. This results in a much more expensive repair than simply replacing the bolts in the first place.

Do you lubricate head bolts?

Yes, you should lightly oil head bolts when you install them. You don’t want to have the bores full of oil or anything, but lightly lubricate the threads and heads. Torquing a bolt that size dry will give an inaccurate and insufficient torque because of the friction of the bolt head against the head surface.

What is TTY bolt?

A torque to yield fastener (TTY) or stretch bolt is a fastener which is torqued beyond the state of elasticity and therefore undergoes plastic deformation, causing it to become permanently elongated.

What grade are TTY bolts?

The TTy bolts you will get from GM (or any pedders dealer) will be of the metric grade 10 variety, and they will have blue loctite on them. So yes, if you can find the exact same size bolts in a 10.9 locally, you can use them.

How many times can you use torque to yield bolts?

What is a torque-to-yield bolt? It is a one-time-use fastener that is designed to stretch during the torquing process (installation). Because of this stretching, the integrity of the bolt is compromised. These bolts cannot and should not be reused due to the stress caused to the bolt during its first installation.

What happens if you don’t torque to spec?

Insufficient torque

When you apply exactly the right amount of fastening force, you can rest assured that the bolt will transfer the ‘hits’ as well as the load of the belt to the bulk of the engine, which will absorb them. … This, in turn, will lead to incorrect belt tension and, eventually, to belt and/or engine damage.

What is the purpose of torquing?

Torquing is the most commonly used way to achieve fastener preload with bolted joints. Torquing produces this load through rotational force on a nut or bolt head.

Why do we need torque?

Torque is a crucial part of generating power from a car’s engine, as it represents the load an engine can handle to generate a certain amount of power to rotate the engine on its axis. … Multiply this torque force (in lb-ft.) by the axis’s rotational speed per minute (RPM) and you get the engine’s power output.

What are TTY bolts made of?

Most of the applications are aluminum. However, TTY fasteners also are used on steel components, because they create a more consistent clamp load on the bolted joint. A fastener is much like a spring, as it must be stretched to provide clamping force.

What is torque to spec?

Recommended torque specifications are unique for each type of vehicle. … By definition, torque refers to the amount of rotational force at the point of application. When attaching a wheel to a vehicle, torque specifications are the amount of force recommended on the hardware to ensure proper installation.

Can you reuse cylinder head bolts?

A head bolt should not be reused if the threads are galled or badly damaged. … Chasing damaged head bolt threads with a die will clean up the threads but also remove material (metal) and undermine the head bolt’s ability to torque down and hold to specs.

Can I replace torque to yield bolts with regular bolts?

With a standard bolt, a technician could torque the bolt to its yield point, and it would return to its original form and length when removed. It has elasticity; it can stretch and then return to its original form. … At this point, the bolt cannot be reused and needs replacement.

Can stretch bolts be reused?

stretch to ensure proper securing when tightened down. (Bolts with Specification: Torque plus Angle). Some of these bolts can be reused, if you torque them to the same torque that you would use for a normal bolt of the same size, pitch, lubrication factor, and strength rating.

When did GM start using TTY head bolts?

GM started using TTY (Torque To Yield) head bolts in 1996 and they should not be reused. However, you should identify the bolts before reusing them.

Are ARP bolts TTY?

No, ARP bolts are not torque to yield (TTY). TTY fasteners, when being torqued, actually stretch because of the elastic properties of the material. This gives them the needed clamping force, but the downside it that they aren’t reusable (well, at least they shouldn’t be reused).

Should I use threadlocker on head bolts?

Threadlocker dries around the bolts and will keep you from getting an accurate torque reading on the head bolts.

Why is cylinder head torque so important?

Torque Limits

Cylinder heads must be tightened to specific torque loads. If too much torque is applied, the cylinder head surfaces may become warped and allow burning gases to escape past the cylinder head gasket.

Why do head bolts break?

Fatigue failure happens when the bolts have not been tightened properly, or have loosened up during its service life. If enough force is acting on the loosened joint during use of the product, bending stresses can weaken the fastener, eventually causing it to fail.