Engine building geek question:
 

I'm assembling another Ford 7.3 Power Stroke diesel engine for my work truck and having a conundrum; the spec for head bolt torque is 95 lbs. on lightly oiled threads in 3 stages, 65/85/95 lbs.

When it was time to bolt down the heads over the weekend, I could not find my little old fashioned oil can, so I poured some oil into the cap of an oil bottle and just dipped the bolt ends in oil before inserting them in bolt holes. Of course, everything was pristine clean, bolts/block/heads. I guess I thought that the oil on the ends would be forced up the threads and coat all threads as bolts went in. That did not happen and when I did the final torque, (95 lbs.), it was very apparent that I had hit dry threads by the increased friction and resistance to initial tightening.

The correct protocol is to completely wet the threads w motor oil and let it drip off, hence "lightly oiled." Even though the early 7.3s had a factory spec of 85 lbs., I'm really OCD about engine assembly and this is bugging me. I was thinking about removing each bolt one at a time and re-oiling, then re-torquing. There are 18 bolts on each head.

#1) Am I worried about nothing? #2) Any reason NOT to do what I'm considering?

TIA. :cool:

It would suck, but I’m leaning towards removing all bolts and reinstalling them per the manual. That would mean new head gaskets as well.

Otherwise, it would always be on my mind if I was going to have a problem down the road.

We had a Loctite rep give a presentation years ago showing proper use. He had a clear plexiglass block with a threaded blind hole. He put loctite on a bolt and threaded it into the hole. Virtually no loctite entered the hole since the air already in the hole kept it out. Lesson was: put the loctite or oil into the hole and not on the fastener.

Are they the original head bolts?

Aren't they torque to yield?

Did you oil under the head of the bolt or washer?

Also, I think you are worried about nothing. You do not hear of 7.3' spitting out their head gaskets very often .

I just spoke with a certified tech that has done dozens of 7.3s.

He said that taking 1 bolt at a time is OK to do, he would. But, that you would problably be OK if you did not.

Yes and no.

As I stated, they are torque-to-number, not TTY.

I like what NY65912 said, but I’m certainly no expert. I’d be curious what “lightly oiled” really means. To me dipped and dripped sounds like too much.

No, but would not be a bad idea. These bolts do not have washers, they are just shoulder bolts. The spec is for lightly oiled threads and it’s always worked well on final torque until now.

If I thought that the torque was way off, I’d be with you. Head gaskets are not that expensive. The thing is, everything was fine up through the 85 lb. sequence, so they are all close. I’m just trying to be precise, as we all should w engine assembly.

Completely understand this but the “lightly oiled threads” means that the threads are just wet w oil going in. You would not want excessive oil in hole, that could really change torque accuracy.

True. It’s an over-engineered situation if there ever was. 18 large bolts holding down a 100 lb. slab of iron.

Thanks a lot. I know that removing one at a time doesn’t change anything wrt clamping of the other 17 and probably will for peace of mind. Thanks, all. :)

I used to think it meant using light oil, (like 3-in-1), then I read that they want engine oil on threads but only the minimal amount. If you squirt some on the threads from an oil can w bolt horizontal, the oil runs around the bolt and it’s just right. Nothing should be dripping off when you install them.

A little oil on the back of bolt heads is not called for but seems like a good idea. The whole thing is about not having additional friction screwing up the torque measurement.

That's the crux of the matter. What do they say about re-torquing after initial break in? In my mind I would think the heat cycle would help out a lot in this scenario to get the bolts spot on.

My friend mentioned that the bolts will not have to be re-torqued after break in if the steps below are followed.


"Take out 1 bolt at a time in the correct sequence

4 steps:

On new gasket with lightly oiled New Bolts:

65 ft lbs
90 ft lbs
110 ft lbs
110 ft lbs again

No need for re-torque."

While that is called for on certain engines, not this one. They torque them down once at the factory and then tow heavy for many hundreds of thousands of miles. They are an over-built Diesel engine and the only way to shorten their life is through improper maintenance, which happens a lot. The last couple I’ve rebuilt were “dusted” from people installing a K&N or similar “cold air intake” that allows too much dirt into the intake and destroys the seal between rings and cylinders. It’s very common.

If you ever buy a used one, walk away from anything that has an aftermarket intake and/or evidence of dirt getting past the air filter. Just unscrew the big rubber tube betweeen air cleaner and turbo, it should be as clean as an operating room inside.

If you are thinking about re oiling them, I believe it is common practice to remove one head bolt at a time, when changing over to ARP studs. I know of several guys who have done it this way, without ever removing the head . These were all on trucks that got the wick turned way up after wards, and I know of no failures .

^^^

For 7.3 engines, those are incorrect numbers. The final torque is 95 lbs. and the earlier engines, (‘95-‘97), called for 105, IIRC. I was remembering wrong in post above, the number went down, not up during the production run of the 7.3.

110 lbs. would be significantly higher than factory spec for my engine, which is stock.

Factory shop manual:


http://forums.pelicanparts.com/uploa...1529356261.png

And sure enough, it does say to oil the bolt flanges. Missed that previously.

I'll have to give him a talking to about this. I guessed that it was a 2000.

Funny part is he works for Ford. Maybe that says something ;)

Sorry if this was misleading. Last time I ask him for advice!

I would not be that hard on him. Those master techs have so much info floating around in their heads that it's impossible to remember everything, especially numbers.

Always check the book, (and the TSBs if they supersede). :)

IMHO, the dry feel friction you felt was not the threads but the dry flanges. Doesn't matter one bit, still the same problem of achieving the exact torque. So, will you remove one at a time? I assume these are not single use bolts.

It's been many years since I built an engine but IIRC if you remove all the bolts and start over you would need new head gaskets. A small price to pay for your confidence that things are correct. Since the engine is apparently out of the truck on a stand, it would seem easy to re do it.

Only my opinion.

I looked on the Ford Powerstroke forum which I used a lot when I had my 2000 F350 with the same engine. I also called the fellow I raced with who works at a diesel repair shop just east of San Diego and posed your question. He and the forum both said the head bolts are single use only as the stretch and due to the metal they are made of will not stretch correctly if you try to reuse them. He said he dips each threaded end in some engine oil (new and clean) and sits them on a shop cloth to let excess run off. He uses an acid brush to oil the seating surfaces just before they get closed up. He also noted to not remove a stud at a time due to the need to replace them and once you remove the head due to wrong bolt tightening you have to use a new head gasket.

Off with your heads!

Sounds like it would be easier to do it right now vs worry later. You can’t really base the decision on that engine’s history, as it’s based on engines that were assembled correctly (if there is a difference).

I have a spreadsheet at work that calculates the % of yield on different fasteners based on toque and friction factor.
The difference between dry and lightly oiled with machine oil is huge.
It takes almost twice as much torque to reach the same % of yield with dry threads.
But ..... if there was oil on the threads and it had a little time to soak in, consider them oiled.
Even if the majority of the oil was wiped away or pressed away or whatever, it's still there and working. It gets into the pores and that's where it does the work.

Here's an interesting study we did one time:
We took two identical centrifugal pumps driven by 40 hp motors. we assembled one pump with new SKF ball bearings with no lubrication whatsoever except the preservation film they were shipped with.
IIRC the radial bearings were 6310 C3 and the thrust were 7310 BECBM.

We assembled the other pump but soaked the new bearings in shell turbo 32 mineral oil for about 10 minutes prior to assembly.
We started both pumps under load with no lubrication.

The pump with the bearings we soaked in oil ran for over 24 hours but was obviously eating itself up by that time.
The other pump lasted less than an hour before vibration levels exceeded safe limits (approx .8 ips).
Most of the pumps at that plant ran on nothing but a very fine mist of oil that was barely visible.
And that's all they needed.

There was a great point made there about "shipping preservative or oil" and I remember when a couple mechanics in #2 engine room on the USS Enterprise reassembled a sea water cooling pump with new bearings and did NOT grease the new parts. The pump ran about 10 minutes before it seized and ended up ruining the shaft as the inner bearing spun! We had two of those pumps in each reactor plant and no more spare parts so we sweated bullets while off the coast of Vietnam until Ingersoll Rand could get us a pair of shafts and several sets of bearings! Fortunately the case was not hurt, not sure why, guess the outer race was nice and tight?

Single use. Well, there you go. It's do over time.

Are you sure that he was thinking 7.3 engines? I have the entire FSM pages for engine assembly, (posted a screenshot above), and it does NOT specify using new bolts. And it is very detailed. I’ve never used new head bolts. No one I’ve ever known or read on a forum used new bolts. If you go to a dealer parts counter and ask for all new head bolts for a 7.3 Powerstroke, they will look at you confused and ask, “why?”

Ford sells a comprehensive rebuild kit for the 7.3 under a Motorcraft part number that has not only everything you need like new pistons and every imaginable part, plus things you really don’t need, like a new oil cooler. It does not come w new head bolts, because you don’t need them.

So I’m going to say those people are mistaken. I’m OCD as all get-up when it comes to building engines and I would never cheap out on something like that. If new bolts are specified, I get them, period.