So another off-the-wall from me.


I've been working on my progression of videos and one right now is titled head bolts, heads, and gaskets. I may need to break this down into three. Anyway, looking at the TTY and ARP stud situation, and I need to call ARP back and try to zero in on this.

The shorter version without a lot of writing. And trying to use on-line data so I don't seem off the wall without going too deep in the weeds or making up data.
















My graph with all the data I can grab. When the TTY method is applied to a bolt it is not yielded to a weaker state, it is strain (work) hardened to a higher yield point. We don't toss TTY bolts because they are weakened, we toss them because they have been stretched to higher yield value, and without an Instron, there is no way to know what the retightening angle should be to get back into yield mode. It's stronger with a higher yield, but less ductile, and the angle tolerance is more critical. The Modulus of Elasticity doesn't change.

The advantage of a TTY method (any bolt can be TTY) is the clamping force is obtained equally across all bolts by the dislocation of the metal, not the variation of friction when using the Torque method. The surprising thing is where the clamping force is between a TTY 10.9 and ARP A2000 using the stated methods.

Ferry C&S seems to have been dissolved between 2011 and 2019, so I haven't been able to find out what the 118R designation means. Any specialty fastener can have any designation on it, ARP does too. Is it arbitrary 118R or a hint to 11.8 value? Mahle's head bolts are the same as the Nav/Ford, made by Ferry C&S with the 118R designation. I haven't gotten a set of FelPro's.

ARP has the torque at the normal elastic region for bolts, which is lower than the TTY for the same diameter, but it looks like the same clamping force. Again, I'm trending that we do not have a bolt stretch problem, we have a too few bolt problem and heads that want to tent in the center because of too few bolts and the head design.

Not sure what we are gaining. Maybe someone knows better.......but not the subjective BS.

 

When I spoke with an ARP Engineer on how to properly install studs and torque them down, he mentioned that the key to getting the best clamping force was to:

-Follow their torque sequence

-When torquing, use 1 fluid motion of possible. I.e. try to avoid small turns, use big pulls until the stud reaches torque value.

-DO NOT OVER TORQUE, that being said, unless you have a calibrated torque wrench from Snap-On, Matco, Cornwell etc. there is usually a 4% margin of error meaning that a harbor freight torque wrench could be off by as much as 4%. This is why if I end up having to use one of those, I torque to 220 or 225 instead of 210.

 

I've got other data that shows how the torque can be all over the place due to friction. The margin of error for the torque wrench is one thing, the margin of error for the friction is another.

I agree that with the Torque Method, staying in a smooth motion and not getting into the static/dynamic small steps is the proper step. Actually, it should be done with any tightening method.

My points,

The use of the second methodology of preload, then angle to tighten (TAT) takes the friction and wrench calibration completely out of it, you stretch to a predetermined length. And while doing so, you allow the deformation to control the bolt tension for better consistency across all bolts. ARP goes nuclear with its lubricant to reduce the variability of friction, a different method and there is no data to looking at consistency, not saying there is when using it. TTY is the same method as TAT, it just takes the bolt stretch to a higher degree.

The second point, we tend to look to ARP studs as providing a higher clamping force then the TTY bolts. They don't, they are in the same range. When you get into the deformation of the block and head under clamping loads, more is not necessarily better. So we are spending a lot of money on a very, very well made stud, to clamp at the same force. Youngs Modulus is the same, we are not changing the elasticity of the fasteners. We have a clamping force issue down the center of the heads. Humping down the fasteners if you went higher in clamping force is not going to help that.

Mahle has a good pictorial that shows what I'm seeing with pressure contact tracing and is shown in many examples of using Fuji-Film Prescale. Clamping higher pulls up the area around the bolts in the block and distorts the head in the bolt area more. You can cause more of a gap in the center of the head due to the distortion. Which may be why ARP limits the clamping force at the OE level. There is a lot of room for the stronger stud to be increased in tension for its hardness.





Hiigh compression loading at the fastening area - FujiFilm Prescale.








The subtitle in the video I'm trying to produce states we are chasing the wrong horse. Not bolts, somewhat gasket, mostly head creep. The stainless o-rings pre-tension the heads in the center, the same that thicker fire rings in gaskets would do, maybe more so.

When we look at gasket failures without a loss of coolant in the heads, head bolts, studs, and OE gaskets, we see the failure right down the centerline; tenting heads. I've got dozens of these images from all the forums from the last 15 years. It's really no different than many other motors, including gas-fueled, we just see more of it. But maybe more related to the resultant stresses of induction hardening the valve seats, with the resultant creep. Both heat and pressure will move the creep to a more aggressive and shorter time period. Variations in the head castings would also move the creep phenomena to another level, why some trucks fail earlier than others, and maybe more often for the one set of heads.

 

If torque was super critical, I would assume (always risky) they would spec a specific stud stretch, measured with a dial indicator on the stud, or an degree/angular torque (torque to X ft. lbs. then tighten Y degrees of rotation) rather than traditional torque. Traditional torque with high quality, calibrated equipment simply is not very accurate. 5% +/- is the best case scenario, commonly it is worse. That being the case I would not blindly torque to a higher value "just to be sure" torque errors can be plus or minus and there is a long list of variables that affect it. I would recommend using a torque wrench that has been tested so you know what it does and following the torqueing instructions to the letter...everything matters Good luck, Russ

 

That doesn't address what I'm posting. No one is saying the torque should be higher, far from it as I posted why it shouldn't. It's worse than 5%.

 

I agree, I was addressing Toreador Diesel's response that had recommended raising the ARP torque number due to having a Harbor Freight Torque wrench. Russ

 

I’m sorry, mistook the comment.

 

Not to muddy the thread but I torqued my ARP2000 studs to 225 in ten steps instead of three using a Teton torque wrench. My heads were o-ringed so probably not applicable to this thread. Just an FYI I guess, still holding strong.

 

That would have brought the tension up less than 10% of the stated value, not a worrisome amount IMHO. Their target is at normal clamp load percentage, the yield is so much higher.

 

Love this kind of analysis. Rather than assume all the stories are true, analyze in depth if it makes sense.

As a question then. Why is there this meticulous process to ensure the heads are flat when resurfacing them. If you know they will tent at some point because there are too few bolts, why not surface them to account for this tenting?
Have a wave like surface on the head where the tent prone areas will sit slightly higher (assume that would be the low bolt pressure areas) than the high bolt pressure areas. When head bolts/studs are tightened the slightly higher areas would have more clamping force and be less prone to tenting.
Then again maybe this is a stupid idea, or not possible.

 

LOL, I was thinking about that, especially when looking at this image after lapping them. That's not machining I would want to do with the standard automotive machine shot mill.

I haven't seen anyone else comment that these heads "tent". I don't think any looked for it.




Those measured under my 0.0005" feeler gauge, and later after going over them again, minor light under the straight edge. (My head lapping video).

But what you said, "When head bolts/studs are tightened the slightly higher areas would have more clamping force and be less prone to "tenting" is exactly what the head gaskets do, especially the FelPro gaskets, which are thicker in the fire ring then the OE, as do the o-rings. As long as it conforms. There is another issue I found with the OE gasket.

In the last TSB relating to checking head flatness, Ford got all hyper about changing the criteria, and the change from a machining perspective makes a big difference. We need a good flat material to start, it's going to creep, but we need to no do things that enhance the creep, and we need to pretension for the creep.



Images I have for the video I'm doing. The second is a Prescale pressure image when altering torque sequence, but in both cases, the proud fire ring has a higher contact pressure.






Carbon paper impressions from the initial lapping work on my engine heads and block. You will still have upwelling from the block at the bolt holes and high compression under the head bolt holes.

 

Another way to look at the waviness issue. And gasket loading along with clamping load necessary for diesel combustion pressures.

 

I wonder what effect differing grades of cast iron and/or aluminum used in manufacturing the various heads has on the tenting when torqued and during changes in temperature....many aluminum alloys expand more than cast iron when heated. Hmm Russ

 

The casting process can have a lot to do with it. My old company had major activities in the casting of railroad and other products, but I did not pay significant attention at the time. It wasn't until the mid-90s, when we were all deep into rotor issues, that I got a handful.

The tenting of heads is not new, a number of engine designs have done it, to the point where OH cams have had binding issues. I remember heads moving being an issue in the 70s when I worked at a machine shop while in college. There are some normal head castings that do the same, and well as other castings, often machinists are used to it right after machining. It follows the standard creep diagrams. You can have hot or cold rolled steel do it too after machining.

The funky thing is you can reset creep after re-machining; you've changed the stress.

From my experience, when a supplier has an issue, Ford sends in several levels of teams, depending on if QC or design issues, or they boot to another supplier. No proof, but I have a suspicion that was part of the "commonized" head change, but the post change engines still had gasket issues.

The 6.4L does not have the same head issues. Some say its due to the increase in head bolt size to 16mm, I'm not so sure about that. More power, more clamping load. The 6.4L is punched to allow more coolant to flow in the center of the heads, maybe something, maybe just needed for the higher power.

Maybe I just need to lower the vitamin loading.

 

First of all: Jack another great piece of work! Why I quoted AK is: wasn't somebody making aluminum heads for our 6.0s? Whatever happened to them and did they work any "better"?