Fun subject, not really. I wish the 7.3 used larger hold down bolts !

No symptoms, but thought I'd check injector torque as loose injectors is bad JuJu. When I replaced my injectors, I used Brake cleaner in the hold down bolt holes, blew them out and used new bolts with blue loctite. A couple month's later, did a hot torque on them and got about a quarter turn to 125 in/lbs. Yesterday I decided to check the hot torque and again got about a quarter turn to 125 in/lbs. Each injectors needed a nearly identical amount of turning to achieve proper torque. Not sure when this stops, but I guess I'll need to check this again in a few months.

 

Once you twist on them (hot or cold) after they are installed with the loctite, you've broken the loctite loose and it's no longer providing any benefit.

In my opinion, the biggest key is getting the injectors all the way seated to begin with. The o-rings are fighting you while trying to push the injector in there. If you don't get it 100% seated, then you're resting on the o-rings and will require re-torquing until it's fully crushing the copper washer.

I'm also of the opinion that you are pushing against the o-rings to a certain extent even when you think you're fully seated and the specified torque values are not enough to properly crush the washer during initial install. Tugly disagrees and believes you just need a good hot torque.

Whichever you believe, just keep in mind, that when you re-torque something, if you want the loctite to hold, torque it down, then remove the bolt to apply new loctite, before re-installing and re-torquing.

 

Not telling you which to believe... just explaining our difference of opinion and allowing you to form your own thoughts: F350-6 feels you are pressing down on an O-ring in there, effectively pinching it to form a seal. I hold the opinion the O-rings are outside a "piston" that slides into a cylinder. The O-ring seal is on the walls, not on some face that bottoms out.

The only seal that "bottoms" is the copper washer around the injector nozzle. This is held flat by a "see-saw" of a lever on top and the two bolts that hold them down.

I use a slow-setting thread locker (blue) and I hot-torque as quick as possible after installing all bottom bolts at the same time. I have an engine warm-up tune that keeps the EBPV closed full time while idling. It takes about 15 minutes to get the engine from dead cold to operating temperature, and that is well before the set time of my thread locker. I hot-torque to 130 (with a wrench set by an electronic torque "verifier" I rigged up) and button it up.

It took me many months, a special tune, a purchase of an electronic torque adapter, and dozens of times under the VCs to develop my method... but it's the only thing that works for my engine.

 

I'm with Rich on the o-ring causing any side effects to the injector torque. Is there some minute resistance? I'm sure, but I doubt any here can measure that small number.

 

We've seen it multiple times here. Folks who achieved the proper torque specs without fulling seating the injectors and it lead to problems. That's why the old recommendation was to hit the solenoid with a rubber mallet until the sound noticeably changed to be sure the injector was seated before trying to torque.

If you don't believe me, pull an injector, replace the o-rings, drop it in the hole and tap it with your hand, then torque it down. After you've reached the specified torque, whack the injector with a rubber mallet a few times (you're not going to affect the crush washer doing this) and check your torque values again. Are you still anywhere close to being in spec?

 

I could see that would be possible and wondered if it could be done without damaging anything on the injector.

 

FWIW, when I installed the injectors, I used a dead blow to seat them until I heard the solid sound one is seeking with this method. I then used a straight edge across them to confirm they were level with each other. I understand and agree with the loctite being defeated with additional torquing but so be it. The factory didn't use Loctite.

 

1. I use a dead blow with a socket extension and strike the point where the bolt will go.

2. I can hear and feel the injector fully seat against the copper washer.

3. I use a straight edge to make sure all are level.

4. I have torqued many injectors that are still "factory fresh" - even on OBS engines. They are never fully torqued, and the engine is quieter after a hot-torque. I'm not saying the factory should have used Loctite, but I will say this became a "thing" because the factory upped the injector bolt torque spec... and one might wonder why.

 

Oh, trust me, you whack an injector solenoid with a dead blow hammer, you ARE going to deform the dead soft copper crush washer....until it won't be deformed any more.

I'm certainly not going to build a gauge which simulates the injector bore and measure the initial clamping force of the injector hold down system....but, it could be done.....and SHOW the clamping force and how it changes when the crush washer gets crushed more. But to think that the friction of the o-rings against the bore is what is causing the torque valve to change? That isn't anywhere near the cause.

 

Have you ever looked at a crush washer after installing an injector with your hammer? The one where you're whacking it hard enough to deform the washer, but not hard enough to damage the injector cups? Have you ever tried torquing an injector down without seating it or even touching the crush washer? If it's not the o-rings providing resistance that require you to whack it in the first place, then what is?

But I'm sure you and your dead blow hammer are right. Please ignore me.

 

Yes... the tight fit of the O-rings resists inserting the injector - that's why the injector needs to be heavily lubed before installing.

Food for thought: When an injector is loose (up to a point), it doesn't bleed oil or fuel. What does leak into the cup is combustion gasses. Once the combustion gasses either compromise the bottom O-ring or the injector becomes exceedingly loose - only then do we see a fluid bleed or mix with something else. The diameter of the injector holds the seal of the O-rings against the cup and head, but the torque holds the copper washer against the bottom face of the cup.

This sounds more like a dispute of how things are worded than one of how things work in there.

 

I am of the school of thought that the O-rings provide resistance which, in turn diminishes the pressure at the bottom. Yes, the injector should bottom on the washer and that resistance should be overcome but...it provides backpressure of a sort and eats up some of that torque (in my mind and maybe in my mind only). Use of the injector and quite possibly the heating of it and its cup seems to release that resistance. Is it because of the jackhammer effect and the vibration, or is it because the O-ring softens as it heats and sinks in a little more, or is it because the cup expands and releases some of the pressure on the in O-rings? Or maybe a combination of the three? I do not believe that there is enough heat there to expand the length of the bolt to loosen the torque. As prevalent as this seems to be and as much as it's discussed it is surprising that there hasn't been a meeting of the minds on it.

 

Ever spent any time working with hydraulics? Maybe a o-ring on a spool valve? How does the spool valve ever move in the bore if the o-ring is "resisting" to such a degree that it would effect the torque of the injector?

And perhaps, just maybe, if you'd lay off the snark, we could have a discussion....But I rather doubt it will happen.

 

What is a spool valve? And I have two toilets that have O-rings in the plunger that have to be disassembled and siliconed every couple of years because the O-rings bind up and stop the plungers from seating.

 

Actually, yes I've played with hydraulics some. Spool valve isn't the same situation as we have here.

I agree.


But then again, it takes two to tango and absolute opinions tend to not leave any room for discussions, only snark comments.

Tugly and I have disagreed about this particular thing for some time now. I have no issue having a discussion with him on the subject and have several times. I have no problems with him and don't make any snide comments towards him either.

It's only when someone claims to know more than everyone else that I tend to take exception. (especially since you never addressed your personal experience with the topic on hand, namely our 7.3 injectors as opposed to spool valves )