Mucci

I'm wondering if it's a requirement to replace the head bolts while doing a head gasket job on the 3VZE. The Toyota head gasket kit doesn't seem to come with them as part of the job.

Mine's an '88. No free recall unfortunately

slacker

iTrader: (1)

YES , they are torque to yield bolts



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Mucci

Ok, thanks

slacker

iTrader: (1)

lots of people reuse them with no problems , but for the cost just do it , fixing a broken head bolt is not fun


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scope103

The head bolts are NOT "torque to yield" bolts, and can be reused.

Don't believe me? Ask Toyota: http://www.toyotapart.com/3VZ-E_CYLI...T-EG98-002.pdf

That TSB was written for trucks 17 years newer than they are now. (Geez, who would expect a truck to last for 27 years?) So go ahead and spring for the $45.

Mucci

The hell does this mean?

"IF ANY ONE OF THE BOLTS DOES
NOT MEET THE TORQUE
SPECIFICATION, REPLACE ONLY
THAT BOLT. IT IS NOT
NECESSARY TO REPLACE BOLTS
IN SETS. ONLY THE BOLT(S) THAT
DO NOT MEET THE TORQUE
SPECIFICATION SHOULD BE REPLACED."

The only way I can imagine figuring out a bolt "does not meet the torque specification" is it snaps.

Tfalley

The reason the bolts are tightened as they are, 33 ft lbs, 90 deg turn, another 90 deg turn is that they are indeed TTY bolts. Standard non TTY bolts might be torqued in a graduated series of values, but to an overall final spec value.

Do not loose the washers, they are "special" and may or may not come with the bolt set.

TTY bolts are engineered to yield at a given value, which is supposed to make for a more even overall clamping force across the head. It takes a pretty good "heft" to make the final 90 deg turn, if one is yielding too easily it should be apparent.

scope103

Tfalley -

You're confusing Torque to Yield with Torque to Angle.

The point of tightening any fastener is to stretch it; it acts like a very stiff spring holding the parts together. Measuring torque is only an indirect measure of stretch, but direct methods are very difficult. But when bolts are very tight, all the friction in the system (bolt-head to washer, for instance) means it takes more (and not well known) torque to get a certain amount of stretch.

So when you have a tight fastener that must be very precisely stretched, you first torque to some moderate value (like 33 ft-lbs) where friction isn't as much of a factor. Then you stretch the bolt a precise and easily measured distance (by turning it an easy to measure number of degrees), and Hooke's law gives you the amount of clamping force.

Torque-to-yield bolts are a completely different technology, and those bolts cannot be reused. Naturally, they do require precise tightening, so they are usually tightened with an angle method. But just because you use an angle method (like on Toyota head bolts) doesn't mean it's a Torque to yield bolt.

This article might help: http://www.enginebuildermag.com/2001...rque-to-angle/

Unless, of course, you're telling us you know more about Toyota head bolts than Toyota does.

MudHippy

Bingo!
1. These are TTT not TTY. http://www.enginebuildermag.com/2001...rque-to-angle/

2. That's not usually the case. From what I've heard. But I've reused mine 3 times without breaking any. So I wouldn't know for sure. But in general, high grade hardened bolts don't tend to stretch much without cracking.