On VW diesels when we do a cylinder head, the TTY bolts are torqued and then given 1/2 turn.
Warm it up, pull the valve cover and give them another 1/4 turn.
1000 miles later, another 1/4 turn.
That adds up to one full turn beyond the torque spec, just to provide the correct clamping load to the head gasket.

 

Dan... that term "clamping load" is one of those funny little things I had never heard about before this week. It is fascinating (to me, at least) to learn how you can tighten a bolt to the "proper torque" and still not have the intended or designed "clamping load".

I'm not suggesting that your approach is by any means wrong, Dan, but for those of us who might choose to go beyond the "torque spec" to ensure proper clamp pressure, it's sometimes easy to go too far and break the bolt either with the wrench or when it's stressed again after being placed back into service.

 

Bump for the good of man kind.

 

this is for the ARP studs

http://67.19.132.3/dieselinnovations...stallation.pdf


the H-11 head studs TQ differnt..i cant seem to find the PDF on that one right now..

 

I was already subscribed to this but dang, there is some amazing tech in here. Looking forward to seeing you fix your problem and teach all of us something!

 

Well of course the head bolts or studs are stretched by much more than the 0.001 in due to differential thermal expansion or there would be quite a leak! Since head gaskets fail due to excessive CP=Cylinder Pressure just how much CP can a head gasket withstand?

A head gasket's MSP=Maximum Sealing Pressure psi is given by MSP={clamping FORCE}/{material AREA} psi where the clamping FORCE lb is provided by the head bolts or studs and the material AREA in^2 is the area of head gasket material that's between the cylinder wall and some critical passage like for oil or coolant to flow between the head and the block.

For example if the head bolts provide a 3,000 lb clamping FORCE and there's a 0.5" x1" section or 0.5 in^2 area of head gasket material between the cylinder wall and a coolant passage the MSP={clamping FORCE}/{material AREA}={3,000}/{0.5}=6,000 psi.

However to provide a 50% safety margin to account for the strength of the head gasket material itself and for variations in clamping FORCE due to material deformations resulting from surface irregularities, temperature variations, bolt patterns, etc.., it's probably a good idea to limit the maximum CP to about 3,000 psi. Well a CP=3,000 psi is about twice as high as you'd get from a stock engine but it's about equal to the CP I estimated for your engine!

Torque locks tension into the head bolts or studs and this provides a clamping FORCE that depends on the tensile strength of the material. For example a stainless steel (AISI 302) bolt has a tensile strength of 75,400 psi so that a 1/2 in diameter bolt which has a cross sectional area of about 0.2 in^2 has a yield strength of (75,400)(0.2)=15,080 lb and such a bolt can provide up to this much clamping FORCE before stretching to the point of yielding.

However the maximum tension that can be safely applied to head bolts or studs is typically determined by the threads and not by the bolt itself. Threads are loaded in shear and the shear strength of bolt threads or stud nut threads depends on the thread pitch, the number of threads engaged, and on the material strength.

Since head bolts or studs are threaded into a cast iron block and since cast iron (4.5% C, ASTM A-48) has a tensile strength of only 18,850 psi compared to the tensile strength of 75,400 psi for steel the cast iron threads in the block are the weakest link.

I know this from experience because many years ago just as I was reaching maximum torque while assembling one of my sporty car race engines I had a head stud come flying out of the block and it went half way through the garage roof! That's why you should keep all body parts out of the line of fire when tightening head bolts or studs!

So even considering the limitations of the cast iron threads I still get a maximum clamping FORCE of at least 3,000 lb and that leaves the question as to what's the maximum area of head gasket material that's between the cylinder wall and a coolant passage and someone that's got a head gasket handy will have to measure that area and post it!

 

if it is any count. this exact deal happened to my work truck with the 6.0, they redone both head gaskets though. no gauges other than stock, i do know it would spit out the fluid while towing our 7K lb trailer. the truck is already 9K lbs. but it ran fine, idled fine, i ran it like this for a few months, then one morning, it coughed twice and then was sputtering real bad, it finally let loose.
not that any of this will help prolly. just what happened t me.

 

I believe you can't just remove the thermostat, if I recall correctly. I seem to remember when the 'stat opens to the main flow of coolant, it also closes a bypass port.

Taking out the thermostat won't close off the bypass.

I'd take it out and boil it on the stove with a thermometer.

Pop

 

Actually, it helps immensely. Thank you for sharing it.

Yep...I remember it that way too.

How does the composition of the gasket itself factor into the equation? Comparing a sock graphite impregnated composite with say a copper, or multi-layer steel gasket.

 

Actually, Scott, it can make a great deal of difference, depending on several factors:

1) the material itself (its composition, resistance to heat set, compressibility, etc.)
2) how much clamping pressure it has seen versus it's rated compressibility
3) how long it saw those clamping pressures, and
4) what temperatures it went through at those clamping pressures

I don't have any data on the various gasket materials, but I can get in touch with an industrial gasket manufacturer who was just in our office presenting information on the sciences behind bolted connections and the use of gaskets. If you can point me to where I can get some specs on the different gaskets you mentioned (or at least the manufacturer of those gaskets), I can pursue this, but it will probably take me a day or so to get my sources to respond with helpful information. Just email the info to me at my office email and I'll see the message right away and can make the calls... pete.cleveland@kbr.com

 

Before I answer your question I'll give these quotes from posts #77 & #78 here... https://www.ford-trucks.com/forums/7...it-work-6.html ...and please don't misinterpret this as a "I told you so" deal because I'm trying to understand how the IDM mod and the HPOP mod interact to advance the injection timing and I'll have more to say later about how "pushing the timing advance to the limit" using both mods together increases the maximum CP.

My equation... MSP={clamping FORCE}/{material AREA} psi ...assumes that the composition of the gasket material is adequate for resisting the clamping FORCE and that the gasket material pushes back against the surfaces of the head and the block with an equal and opposite FORCE! If the gasket material is damaged during installation or can't withstand the repetitive pounding of the power strokes and loses its ability to act like a spring and rebound then the actual sealing pressure falls below the MSP predicted by my equation.

Since you realize that "you gotta pay if you wanna play" is an upgrade from a stock head gasket and bolts to a Cometic gasket and ARP studs the way to go? Well it doesn't take much searching to find contradictory views! I'll give my thoughts along with some quotes from reference links.

The Cometic is a MLS (Multi Layer Steel) gasket that's comprised of three layers of stainless steel. This construction is advertised as providing increased strength, corrosion resistance, and the ability to rebound.

A general internet search reveals... "Most late model engines now use Multi-Layer Steel (MLS) head gaskets because they are much stronger and more durable than nonastestos or graphite cylinder head gaskets. Aftermarket MLS head gaskets are now available for many "problem" engines that are known to eat head gaskets".

So the above suggests that a Cometic gasket is the way to go but then you find... "We had problems with the Cometic gaskets"... lil update- test drive complete - Powerstroke Nation ...and I think FN74 said something to this effect during his engine rebuild saga?

Is it possible that Cometic gaskets are too stiff and rigid to allow for the slight movement of the head during high BP operation? Keep in mind that cylinder #6 fires and then immediately cylinder #8 fires so that during the same 1/2 (180 deg) revolution of the crankshaft both rear cylinders on the driver's side bank are trying to lift the rear surface of the head from the block at nearly the same time!

So is it better to stick with a stock gasket? ..."I'm using factory head gaskets with ARP head studs. I know a lot of guys are running stock head gaskets with big HP numbers, they seem to be more than ok for the application. The head bolts are the problem, not the gaskets."... 7.3 Head Gasket Recommendations - Powerstroke Nation ...read this thread because the OP there had a milder version of your problem!

So what's the deal with ARP head studs? ... "These ARP studs are rated at 220,000 psi tensile strength, and provide the clamping force required to keep cylinder heads from lifting due to higher combustion pressures. The studs are manufactured from proprietary ARP 2000 material, with threads rolled after heat-treat to provide optimum fatigue strength. They are centerless ground to assure perfect concentricity."... ARP

Of course the ARP sales pitch fails to mention that the cast iron threads into which the "220,000 psi tensile strength" ARP studs are threaded only have a tensile strength of about 18,850 psi! The ARP sales pitch could've legitimately claimed that studs are better than bolts because 1) studs fully engage all of the cast iron threads and bolts don't and 2) it's easier and safer to apply a full and honest torque to steel nut threads engaging steel stud threads than for steel bolt threads engaging cast iron block threads but I guess touting their "220,000 psi tensile strength" sounds far more glamorous to the unknowledgeable customer!

If you assume that the OEM 7.3L head bolts are at least as good as the OEM 6.0L head bolts and believe this report... "Stud Update: We have tested these gaskets with the ARP head stud option and there was no extra sealing performance gained over factory bolts."... Hypermax - Product Display ...then the higher cost of ARP head studs might not be justified!

Now "these gaskets" that are referred to above are... "Gasket bodies are made from steel perforated sheet metal covered in graphite composite material with aircraft stainless combustion rings." ...and that's close to having groves cut for "O rings" and "these gaskets" would be the way to go but they're only available for the 6.0L engine.

Even with "these gaskets" you're warned... "If you have more than 500 BHP or stack boxes the gaskets will fail." and ..."Stacking of boxes will also fail the gasket. This is using an in-line programmer along with programming the factory PCM. This is due to the extreme timing advance that is produced by both modifications."

...well here we are full circle back to the issue of "excessive timing advance" which was my lead in to this post and my HP comment in my first post here... "That 310 RWHP corresponds to about 375 FWHP and "still pulling strong at 114 MPH" probably corresponds to at least an additional 75 FWHP for a total of 450 FWHP which is 80% higher than the stock rating of 250 FWHP."

I don't pretend to know what the best solution to your problem is because as I always say you need to understand the "Physics" of a problem before you can begin to determine its solution and I still don't fully understand the "Physics" of this problem but I strongly suspect that "excessive timing advance" is part of it!

I'll keep doing some analysis of how advanced injection timing increases the maximum CP but the best way to understand how the IDM mod and the HPOP mod interact to advance the injection timing and increase CP is by using a glow plug hole to measure the CP under full load.

The best way to do this is to use a cylinder pressure transducer and an oscilloscope so that you can see the complete CP waveform which will be similar to the "green" PP, PS Piston Pressure, Power Stroke curve in this graph which is from my computer model for my CAT C7.

Note that even for my relatively puny 300 FWHP C7 the peak piston HP (Blue curve) exceeds 1,000 HP!!! After doing enough analysis to see what's really going on inside the C7's combustion chamber for the stock HP tune I decided not to indulge myself with a "pressure box" to get an extra 30 HP because I wasn't prepared to "pay to play"!

 

Gene... where does this information come from? My limited understanding of bolting and threading is stuck at the rule of thumb which says that "80% of the clamping force is contained within the contact zone of the first three threads". If that rule-of-thumd is true, then how much extra benefit really exists by "fully engaging all of the cast iron threads"?

 

Well guy's we will get Big Blue on the trailer and to the shop ,probably this weekend ,start the tear-down and see whats there . I just hope that we can see the damage to the HG when the heads come off.

 

Yea, what a disappointment it's going to be if you go through all that to find it's something else.

And we all know what that "something else" could be.....

"Course, you have to go through all that if it IS the "something else", too.

Pop

 

Pop I really can't think of anything else that could generate that much pressure only when the boost is up.