Head Bolt tightening (1 Viewer)

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Hey All,

Doing a head gasket job and I finished the head bolt tightening sequence per the 29 ft lb and 90°, 90° method and something felt strange. All head bolts tightened properly, but two of the bolts felt like they had slightly less resistance on their final 90° turn. The two bolts felt like they had slightly less resistance on their final turn.

Is this acceptable? The bolts are brand new OEM parts. I've searched and found two threads where that was discussed and there were opposing views: remove and start over OR just keep going and run it.

I was super careful with this method and I am wondering, is this the head just adjusting to the new tension or is there a legitimate problem? If I remove the bolts again and start over, will I need a new head gasket?

I chased the threads with a bolt and they were clean and and I cleaned them out prior to and cleaned them with brake cleaner and blew them out dry before I did anything, put a light amount of oil on the new head bolts prior to torquing them in place.

This is annoying me and worrying me. Any thoughts?

Thanks
 
I can't imagine what 'starting over' would accomplish. But IF you elect to do so...you should not need a new Head Gasket provided you don't lift the head or otherwise disturb the gasket.

I've heard of others experiencing the same thing...but not with the use of new OEM bolts, so I don't know what the issue (if any) might be.

I will doing this also soon (torquing down head) and IF I run into the same thing (tactile feel that certain bolts turned easier) I would be inclined find the average torque value of the other bolts and bring the 'suspect' ones up to that (even though they are TTY bolts).

When removing my head....I found a single bolt (rearmost bolt on exhaust side, cylinder 6) that was clearly loose when compared to others. IF this bolt offers a disparity when torquing it down....I plan to 'sneak up' on the torque figures of the other bolts (29ft. lbs, then two 90° turns) and match that...regardless bolt angle involved (to a limit of course).

I am not offering this as a solution to your issue.....just putting it out there for your consideration. You might be just fine...following the factory procedure and letting it be.
 
I experienced the same thing! Recently too! Everything done with a lot of attention to detail on the specs in the FSM. On the last turn there were 2 bolts that felt like they stretched. I checked torque on all of them, they were all around 92 if I recall. The 2 in question were the same, but they may have stretched. IDK. In hindsight after my latest issues I would probably elect to remove the bolts according to FSM, get rid of the bolts in question, and then install them again per FSM. I'd also clean out the holes good, some good high pressure air or vacuum. Good luck, seems like there are more HG's than usual now. Post results here :)

Like @flintknapper said, in the future, I may not do the 90 / 180 method, and instead torque to 93ft. lbs.
 
That is normal. That last few bolt should felt slightly lest resistant because as progressively more bolt is been tighten the more clamping force that tight down the head. So the first few going felt more resistant than the last. From my experience, on the first 29lb past i usually do another two past to make sure is 29lb all across the 14 bolts. If you only 1 pass, the inside bolt especially #1 and #2 bolt is not going be 29lb when everthing is tight down.
 
A few additional thoughts on this:
  • I've felt TTY bolts fail during torque, including 1FZFE head bolts, and a true failure is obvious and a very noticeable difference from "normal" in my experiences with them.
  • I've had situations where one or more out of a set of bolts I was torquing turned more easily and felt/torqued different than their counterparts. @azngarage has one good explanation for why this may happen. I've "theorized" that differences in oiling, thread smoothness/compatibility, hole depth and air tightness (you may be compressing oil/air sometimes), variances in the bolts/studs, etc. may be at play but I don't usually know.
  • I personally would not apply more torque/tightening to any of these bolts unless you first completely untorque/loosen them.
My assumption is that you are fine and should be glad that you followed the proceedures so closely and that you used new head bolts. Imagine if you had reused bolts or not attended to detail closely, I'm sure you'd feel the need to dive back in. I bet most, if not all, mechanics feel the doubt/worry that it sounds like you are experiencing after completing a high-stakes (lots of work/$ to redo) job that they don't perform often.

Unless there is a clear issue (doesn't sound like there is) I recommend focusing on the positives of new bolts, clean threads and proper torque procedure done. Once you get a few heat cycles in the engine the worry should be gone :)
 
put a light amount of oil on the new head bolts prior to torquing them in place.

Just a quick question, was putting oil on the head bolt threads listed as an installation step in the FSM manual? The reason i ask, I've seen service manuals list installing head bolts both clean and dry, and with lube. The difference between lubed threads, and dry threads, will change the bolts turning resistance, thereby changing the amount of force/torque needed to turn the bolt to it's finial position.
 
Just a quick question, was putting oil on the head bolt threads listed as an installation step in the FSM manual? The reason i ask, I've seen service manuals list installing head bolts both clean and dry, and with lube. The difference between lubed threads, and dry threads, will change the bolts turning resistance, thereby changing the amount of force/torque needed to turn the bolt to it's finial position.

FSM does specify using a 'light coat' of engine oil on the threads AND under the head of the bolt. But it might also be a good idea to 'chase' the threads in the block before beginning.

HB tap.jpg
 
That is normal. That last few bolt should felt slightly lest resistant because as progressively more bolt is been tighten the more clamping force that tight down the head. So the first few going felt more resistant than the last. From my experience, on the first 29lb past i usually do another two past to make sure is 29lb all across the 14 bolts. If you only 1 pass, the inside bolt especially #1 and #2 bolt is not going be 29lb when everthing is tight down.

My heart sank when the 2 bolts suddenly felt a little easier to turn on the final 90° torquing. But I was also thinking (fantasizing) that it might be due to the head being cold and stretching out and getting quenched along with the new gasket. I tried to make myself feel better thinking that this is literally the reason Toyota used this technique for torquing precisely because upon assembly using a torque wrench would offer inaccurate resistance for a proper reading. I am sure I am being delusional about this because the 90° method still requires use of a torque wrench for initial 29 ft/lb sequence.

Right now I have the cams installed and would need to remove them to access he head bolts to loosen and re-torque them should I decide to do that. I REALLY would prefer not to release the pressure on the new head gasket as that must distort the crush it has from the first sequence.

Definitely bummed me out considering I bought new head bolts to avoid this specifically and was meticulous about tightening everything up.
 

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