Another Head bolt question/problem

Hi there, I joined recently trying to find info on head bolts for my 06 head gasket project. I found the bolt vs stud thread on here and I have never dug in this deep for repairs but can’t bring myself to pay the going rate shops charge for this repair. I did get factory gasket set and water pump but couldn’t bring myself to spend 10+$/bolt so ended up with felpro at about $50 set thinking they were hopefully better than eBay 39cent head bolts . Finally got to point of torquing down bolts and wanted to follow the actual torque after the initial 27lb and then 180 deg. Thinking that discrepancies in final torque could be part of the problem of failures in these gaskets.
I torqued bolts down in 10 lb increments and at 70lb was getting close to the 180 deg final torque but varied per bolt and some bolts turned easier and farther than others per 10lb. If that, or any of this, makes sense.
On drivers side head some of thd bolts were 80ftlb and still not at 180deg and one of the bolts I believe stretched/stripped/failed as it got easier to turn at the last of the 180. And that bolt is intake side between cyl 4&6.

Now wondering what to do, if I should try to replace that bolt or if that may stretch adjacent bolts or any other options?
Thanks for any responses that may help.
Please forgive any typos, dropped phone the other day and can barely read thru all the cracks...

 

Steve,

I feel your pain on this.

Head bolts are really not bolts but machine screws as they are threaded into the block. Therein lies most of the problem with getting a consistent tension in the bolted union for some engines. Securing the heads and getting uniform clamping across the entire surface area of the head gasket (HG) and block is a very important assembly step to assure HG integrity. On the last three engines that I have rebuilt (4.6L Rover V8, Lotus 907 and 3VZ-E) and had to address this step I have used and will only use ARP head studs to do this job.

The stretch needed is very important and getting all of the studs or bolts to manage this evenly can be a challenge. The studs offer advantages over the stretch bolts because of several design features that make this a better choice for critical engine assemblies. First off the ARP stud is deeply rooted into the threads in the block and they do not turn as the preload is applied. When this is an aluminum engine block this is very key factor that needs to be removed from the equation. Secondly the thread form used by ARP head studs where the hardened washers and nuts are threaded use a finer pitch thread form than the threads in the block. This higher pitch thread form increases the leverage and reduces variation that torquing of the nut has as it stretches the stud and hopefully provides more consistency as the tension is increased to specification. When the moly grease is applied and the nuts and studs are run back and forth before installation this burnishes the threads with each other which reduces variation as a load is applied to the thread. It is only then that you have taken the best steps to try and get the same amount of stretch on all of the studs as you apply the tightening pattern and needed number of incremental steps to get the preloading of the studs to a specified level of tension and therefore torque or degrees of rotation about the nut. The key thing to realize is that the alloy used for the ARP stud and hardened steel nuts and washers will always be much more the same than will be the block and a bolt especially when the block is not steel. Torque is a very ambiguous mechanical specification and is affected buy many factors. ARP takes great strides in reducing some of these factors that have to do with the stud and the nut and the washer as the tension increases. Surface finish and the fact that the thread form is rolled into the stud assures the best made fastener is used to keep the energy from your combustion engine going only back into the pistons instead of rupturing your head gaskets.

The 3VZ-E has a notorious internet reputation for HG failure. So far my 91 4Runner which now has ARP's, MLS-HG's, DG-headers, EGR delete and a Flowmaster 2-1/2" HP-2 in place of the CAT with custom made 2-1/2" Cat-back with FlowFX for a muffler, it now has almost 30K miles since the purchase and after the FeldPro HG's let go when it was completely stock and at 235K miles.

Stretch bolts are usually use once and then discard them. ARP head studs can be reused over and over as the tensile yield is not exceeded during the tightening so that should be a consideration!

 

What do you think on the one that appears to be fatigued? Remove and replace? I think I should have verified accuracy of my torque wrenches also.
Looked on ARP site awhile back to research but didn’t see the 1gr-fe engine listed.

Yeah followed the torque sequence and have factory mls gaskets.

 

Steve,
The problem in part maybe that the bolts have been tightened to yield are of questionable quality which is why you are seeing variation in the tightening process. I went through three head gasket jobs on my 4.6L HSE Range Rover and am on number two in the Jensen Healey's Lotus 907 engine but this last time ARP-studs are in the motor with up-rated torque values over the OEM studs that top had topped out at 75 ft-lbs. The first two HG jobs on the Range Rover and one other on my wifes Discovery both used stretch bolts on composite HG's that came from eBay (conduit to China). The method used a preload torque of some value that I don't remember and then two 90° twists of the bolt head to stretch the bolts. On the last around I put in ARP's on the 4.6L V8 and Cometic copper HG's in the hope that I might solve the T-top linered blocks coolant consumption problem. After 18 years of toil in owning this Land Rover I finally sent it to the scrap yard where it belongs. The tensile strength of the ARP head studs is the highest of any fastener you can find for securing heads to blocks. I suspect you have Chinese made head bolts that you are working with even though they are FeldPro branded. China is a nightmare and unlike Japan doesn't know what quality control is for on anything they copy and make. If one in the group of your head bolts has yielded I'd pitch whole lot and do the job over with high quality fasteners that you can get from the Toyota dealer if you cannot see that ARP offers a solution for you engine. You want to do this once and get it right because doing your HG's is not a small feat in work and time. There is a damn good reason the bolts you have were inexpensive!... Also you have to follow the pattern defined in the factory service manual for your engine as you tighten the bolts. That is really important in allowing the composite HG to start seeing even compression as you bear down in stretching the head bolts over the entire head. Usually this pattern starts from the center bolts and sequentially works you out toward the end pair of bolts that are at the ends of the block. Hopefully Toyota designed the 1GR-FE with head bolts that are all the same in length?