© DenLorsTools.com Some head gasket sets come with replacement headbolts included automatically.

Summary: This automotive tech article is on TTY (Torque to Yield) head bolts. Headbolts that stretch require different tools, procedures and precautions compared to using conventional bolts. Improper procedures can result in bolt breakage and head gasket failure. Suggestions in this article help to insure the repair is done correctly the FIRST time.

Most torqueing procedures require several passes. The following example is for a Chevrolet 3.1 Liter engine: In the process of replacing head gaskets, the cylinder heads sitting back on the block; ready to torque the head bolts. The service manual has the proper torque sequence and torque procedure. The service manual also says to use a torque angle meter – first pass 1. torque to 44 foot pounds in certain pattern… ok. 2. Use a Kent Moore specialty tool J-36660-A to then turn the headbolts 95 DEGREES.. what? That’s right, degrees. It’s not as simple as it once was to torque the head bolts. TTY (Torque to Yield) bolts are designed to stretch more than regular bolts. Tip #1 DON’T reuse them. These are a one time use design. Reusing TTY head bolts or TTY bolts used to clamp any other components such as bearing caps or connecting rods may lead to bolt breakage and a costly come-back.

Suggestions when working with TTY bolts.

1. Clean out bolt holes/threads to help obtain the correct initial torque. Any rust or rough threads may affect initial torque, that can affect the tightness of the bolts in the final step.

2. Unless specified by service manual DO NOT use lubricant anti seize or sealer they may cause an incorrect initial torque also. Note that if the bolt enters a water jacket, sealer may be required (refer to a service manual).

3. Reusing Torque to Yield bolts can result in failure. Replace TTY head bolts to help insure the quality of the repair. Like with any rule, exceptions may apply – check the service manual.

4. When removing TTY bolts it may be helpful to first use a hammer and punch to tap on the top of the bolt sharply. Many technicians have used variations this tip for years when dealing with seized or overly tightened bolts. GM actually recommends this in a TSB (Technical Service Bulletin) specifically to help prevent breakage when removing TTY bolts. GM also says that hand tools seem to be the best method to help prevent breakage (although this could be debated).

5. Previously only a very expensive (over $1200) special service tool was available to measure the torque angle (J-36660-A). Then Snap On came out with an option for around $500. Now KD Gearwrench now has a high quality specialty tool at a great price that has a dual purpose (less than $300). It is an electronic torque wrench that has a torque angle meter built in. They are available in 3/8″ drive and 1/2″ – see the links below for more information.

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