80 series head bolt Q

[BionicCruiser]

a buddy of mine has an 80 that blew the head gasket. he is having it fixed. he had some questions and i had him go over to Am. Toy. and talk to Dan. Dan told him the head bolts could be reused IF they met a minimum diameter at a certain point on the bolt, but didn't have those specs on him. i posted in the 80 series section, but only 17 reads and no answers yet. that list moves fast! only a couple hours and it was on the second page already!
does anyone have a FSM or know where to find those specs? thanks.

 

[alia176]

28. INSPECT CYLINDER HEAD BOLTS
Using vernier calipers, measure the thread outside diameter of
the bolt.
Standard outside diameter:
10.85 – 11.00 mm (0.4272 – 0.4331 in.)
Minimum outside diameter: 10.6 mm (0.417 in.)
If the diameter is less than minimum, replace the bolt.

 

[BionicCruiser]

cool, thanks!

 

[juane]

Do head bolts wear out? Or do they get thinner from being stretched?
My feeble brain wants to know...

 

[marcfj60]

When you torque them, you exceed the yield stress by an 'acceptable' amount. So you stretch them out, causing them to neck, or thin slightly in places. It helps to get the maximum possible preload on the bolt to hold the head to the block during heating/cooling cycles, hopefully dealing with the expansion and the contraction of the metals while still maintaining a tight block to head interface.

 

[alia176]

Yeah, what he said.....

 

[Beowulf]

My feeble brain wants to know...

The 1FZ-FE engine uses TTY (Torque to Yield) head bolts and we use TTT (Torque Turn to Tighten) during installation.

Threaded Fasteners Torque-to-Yield and Torque-to-Angle: Engine Builder

The above link explains this very well.

-B-