How do you know if a bolt is torque-to-yield?
You can identify a torque-to-yield or stretch-style fastener by the narrow shank just below the washer face and before the thread run. A bolt of this design is intended to be installed in the plastic range and cannot be reused after being tightened once.
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. They provide more consistent clamping loads, across the entire head-to-block mating surface. Reusing the old bolts can cause expensive engine failure.
Are ARP bolts torque to yield?
Yes, ARP rod bolts can be reused. We don’t reuse the stock bolts because they are designed to stretch when torqued to yield point. The ARP stuff is hardened and does not stretch, which is why we just use normal torque ratings.
Are torque yield bolts better?
Torque to Yield (TTY) fasteners are used in many modern engines. When torqued properly, they provide better clamping force than standard fasteners. All TTY bolts are 1-time use only. However, some rod bolts and main cap bolts can be tightened up to 3 times for assembly purposes.
How does a torque to yield Bolt work?
Stretch bolts for cylinder heads Stretch bolts, or torque to yield bolts, when properly torqued, loose some of their diameter to the stretch, but are elastic, and if variations in the gasket material or other things occur they keep their clamping force by varying their diameter slightly, but frequently, like breathing.
Why do aluminum cylinder heads have torque to yield bolts?
Aluminum cylinder heads expand at a different rate than cast iron blocks. As an engine warms up, bolted together parts have to move against each other or slide on their gaskets. Therefore the elastic properties of the torque to yield bolts, allow movement between parts; yet maintain even clamping loads and sealing.
How much torque do you need for a 5 bolt fastener?
With a 5-bolt pattern, 11,917 lbs. of force is needed per bolt. With a 6-bolt pattern, 9,930 lbs. of force is needed per bolt. This then becomes the initial load needed from each head bolt in order to seal the gasket.
What happens when you tighten a torque to angle fastener?
When you tighten a critical bolt to specs, you’re actually stretching the bolt. As you stretch the bolt, it wants to return to its original length. Based on the quality of steel used in the fastener, the diameter of the fastener and how far you stretch it, the load or force applied to the joint (the two pieces being fastened together) changes.
What does “torque to yield bolt” mean?
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. Fastener. Jul 10 2019
What does torque mean when tightening bolts?
When you tighten a bolt in a bolted joint, you use a twisting force, called torque. Torque is related to bolt tightness , but many additional factors – such as friction – combined into a single “nut factor” can have a significant impact on the relationship of torque to the tightness of the bolted joint.
What are torque to yield head bolts?
Torque-to-Yield (TTY) head bolts are used on many late model engines to clamp the cylinder head to the block. They differ from ordinary head bolts in that TTY bolts are designed to stretch slightly when they are tightened down.
What are the torque settings for head bolts?
SOURCE: head bolts torque settings According to my haynes manual for G-S reg, 1989-1998 it goes as follows, Stage 1:- Tighten all bolts by hand until bolt heads just contact cyl. head. Stage 2:-Tighten all bolts to 40Nm or 30lb ft. Stage 3:-Angle tighten all bolts a further 60 degrees. Stage 4:-Angle tighten all bolts again a further 60 degrees.