Desert Rat

I'm afraid I may have just done something fairly bonehead. I just got my heads done and I'm in the middle of putting everything back together. I got new head bolts and torqued the heads down per the FSM, and installed the cams/bearings. Lo and behold, I notice on my workbench that I didn't install the plate washers that go with the head bolts. Realizing that the bolts are T-T-Y, I'm hesitant to pull them out again just to put the washers on - experience has shown on other vehicles that you can't/shouldn't reuse these bolts.

My question is: am I safe with keeping the head bolts as is, without the washers and if not, can you reuse head bolts on Toyotas?

ChickenLover

I can't say for sure whether you actually need the washers or not. During my top end rebuild I ran into a problem that required me to remove one of the heads again after it had been properly torqued with new head bolts. I was hesitant to reuse the bolts, but I did. It's been almost 20k since, with no problems.

ThomasJ

I would put them on. It evens the load on the soft aluminum. Without them the head bolt holes may collapse and "unload" the head gasket.

I have not seen it happen on the toyota heads but I have seen it happen on aluminum small block ford heads. If you dont use them, the aluminum around the head bolt hole deforms and causes the bolt to lose its torque. I would imagine that the toyota head would be no different. I would not want to take the chance anyway.

tc

From an engineering point of view (the often wrong "in theory"), it is OK to undo the head bolts to install the washers. It would be VERY bad to accidentally install extra washers, then take them out. Here's why:

All threaded fasteners work by elongating and locking together the threads. TTY is a more accurate representation of that than "regular" torquing bolts. The extra distance for the washer will provide that slight extra amount of fastener to stretch ensuring the heads are torqued properly when you reinstall. If you were to go the other way (taking a washer out) you would be trying to restretch a part that was already stretched, and could lead to an inaccurate torque.

Once again - this is just theory. I would ask engbldr for the "real world" answer.

Silver_Truck

when i was helping my dad do his 3.0 rebuild we had the heads on and torqued down before we realized that one of the heads was ˟˟˟˟ up from the machining from the guy he got it from. engnbldr said that it was porbably ok to reuse them because they hadn't been heat cycled.

Desert Rat

Okay, thanks guys. I'll take the chance and reuse the bolts with the washers. Kills me that I was being so careful in the rebuild and missed this.

Radyota

It happens to everyone at some time or another. Good luck, Desert Rat. I was also wondering about the affects of "heat cycling" on head bolts--thanks, Silver Truck! I've been learning all I can about these head bolts before I put my heads back on, and I've found a lot of contradictory opinions! I went to St. Cloud Toyota yesterday to get a new knock sensor wire (recommended on this site) and I asked the parts manager about new head bolts. He said it was OKAY TO REUSE the old ones!! He also said that they USUALLY REUSE the old ones too!! What the?? Makes me wonder if that's why they had so many head gasket issues? I told him that I often visit an online Toyota forum, and that there are master toyota techs with many years of experience that all strongly suggest using all new head bolts. He STILL insisted that it's not necessary! Even after I told him that it's a torque-to-yield fastener that stretches! I try to educate people. :pat: Oh well, he wanted over 10 bucks apiece for new bolts anyway, and I can get them cheaper from engnbldr. What's funny is that I reused the old bolts before on my dad's truck (long before I knew about Yotatech) and it's still going strong! He's probably got 25,000 on the rebuilt head job (250,000 on the truck). I maybe just got lucky. Anyway, this place has a WEALTH of useful information, and I'm thankful to everyone for posting their probs/solutions. I AM going with new head bolts, and if anyone goes to St. Cloud Toyota, don't believe the parts guy. Research your stuff here first!

ChickenLover

That's some good advice. I once had a parts guy at Kragen tell me that my 3vze didn't have a throttle body.

Needless to say, I walked out and never went back.

FastCat

Maybe I'm reading your post wrong, but adding more (or less) washers won't make bolts stretch more (or less). If you apply the same amount of torque on a bolt, it will stretch the same amount regardless of whether it has 1 or 5 washers under it - provided it hasn't exceeded it's yield point!

Re-using a TTY bolt that has been installed already is gamble. A bolt that has already been stretched to the yield point has lost it's elasticity and could eventually fail as a motor heat cycles (causing expansion and contraction). Most reputable engine builders will recommend buying new head bolts, as whatever they cost, it is cheap insurance when compared with the cost, time and hassle of having to replace a blown head gasket later on.

As an aside, there are some differences in "true" torque vs. measured torque, depending on what kind of lubricant you use on the head bolts. For example, using no lubricant at all will cause a measured torque (using a torque wrench) to be read that is actually greater than the true torque on the bolt. The better the lubricant, the more the measured torque approaches the true torque. That is why (typical) TTY bolts final "torquing" is done by angular measurement, not with a torque wrench.

tc

My point was adding a washer will move the nut "up" the bolt, exposing unstretched threads, thereby allowing the TTY method to work. Once the bolt has yielded, there is some residual plastic deformation, and it is now longer (and stronger BTW). This will change the pitch of the threads (albeit very slightly) so a 1/4 turn is not the same amount of stretch that the designers really wanted.

Example: If you take a paper clip and bend it a little, it will spring back just like before - this is called "elastic deformation". At some point, the force required will exceed the strength of the steel, and the paper clip will stay bent a little due to "plastic deformation" after it releases the elastic deformation.

FastCat

The thing is, it isn't just the threads that are stretched, but the entire bolt.

My point about not re-using a TTY bolt is that when a bolt is stretched beyond it's yield point, it is now brittle and can no longer stretch without breaking. When a motor composed of disimilar metals expands (aluminum heads on cast iron block, for example), the disimilar metal parts expand at different rates and the bolts MUST be able to accomodate this expansion by stretching and then contracting back when cold.

Don't be concerned about the deformation characteristics of the bolt, like bending, because these (head) bolts don't encounter sheer forces of any significance, just longitudinal ones.

txchoo

The tech manual says to measure the bolt with a vernier caliper at the elonqate d thread and if it is within the specified values it is O.K. to reuse the bolt. That is the word from Toyota themselves.