What is the correct sequence in tightening cylinder head bolts?
These head bolts need to be tightened in a very different fashion. Normally you would tighten conventional head bolts in a crisscross pattern in three steps, to one-third, two-thirds, and then to the final torque.
What is the torque setting for cylinder head bolts?
Tighten the cylinder head bolts in 2–3 steps in the proper sequence. The final torque specification is 59–64 ft. lbs. (80–86 Nm).
Why are cylinder head bolts tightened to a specific torque?
Cylinder heads must be tightened to specific torque loads. Too much torque can cause bolts to become loaded past their limits when cylinder pressures in the engine rise, resulting in catastrophic failure of the bolts and thus the seal between the cylinder head and the engine block.
Can you over tighten a cylinder head?
Overtightening head bolts can damage the block threads, yield the bolts, and in extreme cases crack the cylinder head. Some heads are actually fitted using torque to yield (sometimes called stretch bolts), where the bolts must be replaced after use, or they loose some of their strength.
Why are cylinder head bolts loosened and tightened in a specified sequence?
“Why is the cylinder head tightened in a correct sequence?” Because the head gasket “flows” under pressure to assume its final shape, and correct distribution of the material and relieving tensions can be ensured by the correct tightening order.
Why are torque specifications important when installing head fasteners?
That’s why you must make sure your head fasteners are in excellent condition and install them properly. Adhering to recommended torque specifications and torque sequences is key to achieving a good, strong seal.
What determines the torque value of a bolt?
These torque values are usually based on oiled fasteners. Lubricate the threads and underside of the bolt head with motor oil or aftermarket lubricant. The slicker the lubricant, the greater the preload scatter (or error) during installation, according to ARP.
How can I improve the accuracy of my Arp bolts?
Some manufacturers, such as ARP, recommend cycling the bolts to improving loading accuracy. This involves torquing the fasteners to about 50 percent of their recommended spec several times before reaching the final number. If you’ve had your cylinder heads resurfaced, you’ve altered their overall height.