I used 140 inch pounds on a hot torque Summer of 2017. It been pretty good since. All of mine were sitting at 90 and #1 was almost finger tight.

 

Why isn't some type of thread locker used for these from the factory, it is very common for anything critical that can't be accessed conveniently.

 

I wish I'd checked mine when I was in there, didn't know it was so common for them to loosen. I wonder if the bolts are actually rotating and loosening or if it's just stretch/wear/settling going on. Many have reported loose ones, but I haven't heard of any coming completely loose.

 

It’s just not necessary? The max temps in this area also likely make thread locker ineffective.

To be honest, I do not use a torque wrench for things that call for this little torque. Unless you are using a high dollar torque wrench and have had it calibrated - you still must use your best judgment when tightening these bolts.

The only harm from over-torquing would be breaking the bolt off in the head. I feel like my extensively calibrated wrist is qualified to prevent that.

FWIW, I’ve never used a torque wrench on a spark plug either...

Maybe the often-quoted 140in lbs is not adequate? That is just under 12ft lbs. Seems really low to me. (Even water pump bolts, etc call for like 20ft lbs IIRC and some of them go into aluminum threads!) Again, there is no harm in over torque until you break the bolt.

Maybe there is something I’m not thinking about here???

I remember when the FTE crowd started the injector torque discussions...

 

I believe someone looked up the max torque specs for that sized bolt a while back, and 140 is pushing the upper limit of what I'd feel comfortable tightening something you don't want snapping a few hundred miles from home.

A Monday/Friday produced bolt and a torque wrench off by 10% could equal a broken bolt in the head

I'm having trouble attaching lab test results pdf for loctite 242 and 243 while mobile. But the thermal cycles and temp ratings are well within our engine's operating envelope. Will try to post tonight from wifi

 

That is interesting...

I am going to say that is not nearly enough and that would explain the FTE injector torque phenomenon.

The injector hold down bolts and rocker arm bolts should be about the same (same size and Seems like rocker bolts call for like 30 or even 40ft lbs????)

I’m tempted to borrow a high-end inch pound tq wrench and see what my ‘calibrated wrist’ is pulling them down to. I typically pull them down as far as my little craftsman right angle impact will go (20-30ft lbs?) and then use 1/4” drive ratchet to give them the final snug. I go to all of the rocker bolts and do the same thing while I’m in there.

I have a few heads laying around here. Maybe we need to do some destructive testing and see what the limits really are??

I completely understand not everyone is comfortable doing what I do. If you don’t turn wrenches often, this is a daunting endeavor. The consequences are extreme and I do know someone who broke an injector bolt (using a tq wrench...) and he pulled the head and found cracked pistons and then ended up rebuilding the engine. Started out as an injector swap......., Y’all are not wrong to give this careful consideration.

 

If that happens in your driveway it's an inconvenience, if it happens on the road later on it could be real sucky. Before a bolt breaks it stretches and becomes weaker, it can later stretch more and/or break in use. I have pretty good faith in my feel in most situations, but I'd still use a torque wrench. There's no reason one can't combine the two.

 

My issue was never as bad as Tugly's but it did quiet down the "sewing machine". After that first time I did it a few more times but my OCD is more than most. Add to that my truck was my daily driver and I put about 25K miles a year on the odometer.

After I installed new injectors (plus hold-down bolts) and hot torqued them there was a question on whether the bolts were stretching or walking out. I did another hot torque about 6-7 months later and put a mark on them at the 12 o'clock position with a welder's pen (recommended by Walleye Hunter) to get a definitive answer on that question. Unfortunately my truck got totaled before I went back for another hot torque and position check of the markings.

As a shadetree mechanic having an expensive precision torque wrench was not in the cards for me, let alone having it calibrated on any sort of schedule. I did, however, try to be consistent with my approach:

1. I used a 0-250 in-lb torque wrench so my target torque was somewhere in the middle-ish of the range (the Navy taught me use a torque wrench from 20-80% of its range to be more accurate).
2. I applied counter-torque at the head so that the majority of the force translates to the tightening force.
3. I applied slowly and consistently for each "pull" to keep things as even as possible.
4. I stepped the torque: 60 in-lbs, 80 in-lbs, 100 in-lbs, then 120 in-lbs (those bolts are small so never had the cojones others did to go past the spec).
5. Every torque met only got the first *click* except 120 in-lbs. For the final run at target value gets 2 *clicks* (tighten to the first *click*, then back off and tighten to *click* again).

I'm sure there were inconsistencies due to the uncalibrated torque wrench but I seemed to have an issue with them loosening. I've had some below 100 in-lbs but never below 80 in-lbs.

As SkySkiJason said, each truck seems to have its own personality and things to deal with. Some are quieter, some get better fuel economy, some injector hold-down bolts loosen, etc.

 

Yeah that's not always the case. Rocker bolts and injector bolts do both take an 8mm socket, but the bolts are not the same. Different grade ratings, and diameters

One could be a 3/16" diameter at the threads, and the other 3/8" @ the threads, but have reduced or enlarged heads for the smaller/larger footprint at the top. I've encountered it countless times before, and had to take a trip from our massive bolt bins to the storeroom for an overpriced specialty bolt. That's why torque ratings for the specific bolt used are important

 

I think we are really reaching to think an ‘over-torqued’ bolt will break later down the road.

I guess if it was on the ragged edge of breaking, the thermal cycling could push it over the edge - but I think there is a good margin between ‘tight enough’ and danger of failure.

I’m willing to sacrifice a head to test this. Perhaps we will put this on the agenda when we have a little GTG here next month.

 

I'm not saying you are wrong and I'm right, just that i definately lean to the side of caution, especially throwing out info on a public forum that little 16 yr old Johnny may take as gospel and after performing his 1st oil change ever buys a 40 yr old Chinese torque wrench from a garage sale that was used as a hammer by the wife and cranks er down on a set of used bolts, then runs into snapped bolts and finger pointing

Like Byron i went above factory spec, but i also have decades of daily wrenching experience and a touch of OCD. After a couple hundred snapped bolts you eventually learn where to stop and feel that point approaching

 

At least it won't be devastating if it does fail.

I had two bolts break off in the head when I was installing injector cups. The loaner tool comes with some bolts to use in the holes to hold the tool in place while you install/remove the cup. I thought for sure I was going to have to explain to my wife why I needed a new head but soon after realized that the bolts weren't bottomed out. I was able to fish them out with a couple of pick tools.

 

I agree 100%, That is why I am cautious to just say don’t use a torque wrench - but also caution that a harbor freight or parts store torque wrench are not fit for lug nuts, much less something as precise as 130in lbs.

I would venture to say that very few people who will read this even have access to a torque wrench I would trust for this job....

 

One of the benefits of working for a major airline in maint is that we have a precision measurement equipment department and that's all they do is calibrate. If we buy the same tools for our personal that the airlines uses they will even repair ours if they need it when sent in for cal. My little Snap on 30 to 150 inch lb is perfect for this job. I'll bring it to the GTG if able. Not sure what the dates are.

 

I just installed my re nozzles pis injectors and torqued them all too 122 ft/lbs. today I pull the valve covers and checked them all cold or 60 in my shop and not one of them was still at torque. Lowest I had was 97 and the rest were all in the 100-102.