Duramax Head Gasket Replacement

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Sounds good.....

Be interesting to see what actually happened...and why the pressure issue....

Robyn,

My thoughts about the causes of over-pressure problems are evolving. My thinking at the present time include:

1- The head gaskets simply wear out over years of use due to the friction caused by differences in the coefficient of expansion rates between aluminum and cast-iron. I suspect there's a direct correlation between thermal cycles and head gasket life (in the case of my GMC - 15+ years and 140,000 miles), at least with the original crimped head gaskets.

2- Head bolt(s) yield for whatever reason (especially when beyond stock power/boost levels), which reduces the clamping load - resulting in combustion pressure leaks. With Lil Red, there's a direct connection in time between a nitrous backfire at the track and the first appearance of the cooling system overpressure... What's interesting is that GM reduced the head bolt torque angle settings (reduced the torque) of the same TTY head bolts when installing the newest riveted head gaskets. Perhaps the earlier/original crimped tabs were interfering with head bolt clamping force.

3- The original head gaskets used crimped tabs at various places around the perimeter of each gasket. These crimped tabs were what kept the multi-layer gaskets locked together. The tabs are thicker than the surrounding gasket and are located between the head/block surfaces - making it harder for the head bolts to effectively clamp/seal the gasket. You can see what effect this has on the gasket and where most of the questionable sealing occurs. The new riveted design has the riveted areas outside the head/block mating surfaces, so they don't interfere with the effectiveness of the head bolts to maintain clamping load over time.

[More Power]

I watched an ARP video a while back where they discussed the "elastic" clamping load supplied by properly installed and torqued Series-2000 head studs produced for the Duramax. I like it that the ~$650 head studs have some elasticity designed-in.

However, we know that GM is still using TTY bolts in the newest L5P Duramax, which is rated for 445 hp / 910 lb-ft - and rated for up to a 35,000-lb GCVWR.

I interviewed the "Duramax Power Tour" team in 2000, who drove an LB7 equipped 3500-series truck towing a 20,000-lb event trailer. I rode in that truck as they wailed on it, on the I-90 continental divide pass just east of Butte, Montana. I asked them if they drove it like that all the time. I was told yes... They put in excess of 20,000 miles on that truck - hammer down all the time. I can also point to a 750,000-mile LLY Duramax used to commercial tow RV trailers all over North America, that I wrote about a few years ago. GM could acquire head studs equal to those offered by ARP (maybe even contract with them to provide) if they felt it was necessary.

I have a couple of debate points about studs that are hard to answer and difficult to challenge. 1- The aftermarket pushes anything that they can sell - ("while you're in there") type of stuff, including head studs. 2- Studs are simply easier to install than TTY bolts. You must mark the heads of each TTY bolt during the two angle tightening sequences or you'll mess up the installation. With studs, you only use a torque wrench. If you forget one or get out of sequence, it's really easy to check what the torque is for that stud. Personally, I think this is why many vendors/mechanics push studs (sell more expensive stuff and they are easier to install). Otherwise, they would/could point to actual durability tests involving direct comparisons between engines using head studs and TTY bolts (fleets would be the best source of information. Second best would be an accumulation of real-world reports from actual owners - like the story I did on the 751k mile LLY Duramax). For most, these head gaskets will wear out long before any real comparison can be done on the veracity of claims otherwise.

I plan to measure the actual torque applied to these TTY bolts after completing the 2-step torque angle installation. We know that GM/DMAX reduced the final TTY head bolt torque angle setting when they introduced the new updated head gasket in 2007. I suspect this was to reduce the Brinelling of the head gasket fire-ring onto the aluminum heads. Knowing what the torque is for current ARP studs (125 ft-lbs), it'll be interesting to learn what the actual torque value is for the installed TTY bolts. The current TTY installation takes the TTY bolts from a static torque installation setting of 59 ft-lbs then adds two separate 60 degree rotations for a total 120 degrees. The original Duramax TTY bolts saw a 150 degree sweep after the 59 lb-ft static tq setting.

[Robyn]

A six and a half with REASONABLE power levels will do fine with TTY bolts.

Try shoving big boost and a buttload of fuel into a 6-1/2 and it will suffer....

I tried a set of MLS gaskets on a 6.5.....NOT ENOUGH HEAD BOLTS IF USING TTY..

ARP studs may have worked better.......

The factory stuff is always right on the ragged edge.....You always need more when you plan on flogging it hard.....

[More Power]

A six and a half with REASONABLE power levels will do fine with TTY bolts.

Try shoving big boost and a buttload of fuel into a 6-1/2 and it will suffer....

I tried a set of MLS gaskets on a 6.5.....NOT ENOUGH HEAD BOLTS IF USING TTY..

ARP studs may have worked better.......

The factory stuff is always right on the ragged edge.....You always need more when you plan on flogging it hard.....

If money is no object, we would all live life differently and make different decisions regarding diesel engine service. Fact is, the ARP head studs are $650 and the factory TTY bolts are about $100.

Take an old truck to a diesel shop or dealership, and ask them to install a new head gasket kit ($400), ARP head studs ($650), new injectors ($2400), new injector hard lines ($650), new water pump ($125), new hoses and an endless list of "as long as we're in there" stuff, and of course at least $5k in labor - and you've made a bad decision regarding financial common sense - i.e. spending $10k+ on a truck that in even perfect condition is still only worth 10K. When faced with that reality, most thinkers will crush/part-out the truck and not spend a dime on it... We didn't even talk about brakes, ball joints, steering components, drivelines, tires, rust... and on and on and on...

Meanwhile, our performance 6.5TD Project ran without a problem to 300,000 miles in 7 years using TTY head bolts (till we sold it), and my 2001 GMC ran to 140,000 miles using TTY head bolts - even with the poorly designed factory crimped-style head gaskets. I get where the ARP stud advocates are coming from. This is partly why I installed ARP studs in my own 2001 GMC LB7 head gasket repair. I spent extra on this truck only because I did the work (and because I needed to install the studs so I could photograph it and eventually write about it). It's just that at some point, all those faced with a significant repair on an older truck need to make a decision... Do you crush the truck or do what is necessary to save it without compromising basic service and dependability while not violating financial common sense? As part of an overall budget strategy, I think the lower cost TTY head bolts fit into that paradigm. And... Lil Red is getting TTY bolts.

What would mean most to me regarding this studs/bolts debate is to study the actual service histories comparing engines built with studs/bolts along with a description of how the trucks were used, and then be able to discern some sort of recommendation from that. Right now, the stud advocates "say" they are better... We can read about tensile strength and a wide range of engineering theory, but what's that really mean in the real world to average truck owners?

[56pan]

"new injectors ($2400)" Are you writing about a 6.5 GM diesel? That's $300 per new injector?

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"new injectors ($2400)" Are you writing about a 6.5 GM diesel? That's $300 per new injector?

That price is for remanufactured Duramax LB7 injectors. "New" as in replacing what was originally there. Prices vary between vendors. You can buy suspect stuff off eBay for less or spend a lot more for newly manufactured Bosch injectors. The $2400 price is for reman from Kennedy. Injector prices for newer model Duramax engines are more.

I had hoped back more than 15 years ago that injector prices would fall for the older model Duramax. I knew that as the truck's book value dropped, a critical point would eventually be reached where the cost to repair exceeded the "drop dead" percentage of 50% of vehicle value.

There is light though... I'll need to spend some time investigating, but it is possible to do what was unthinkable just a few years ago and replace the wear items in these injectors using only basic tools and skills. This, I believe, will become a big factor in saving the older trucks.

[56pan]

If money is no object, we would all live life differently and make different decisions regarding diesel engine service. Fact is, the ARP head studs are $650 and the factory TTY bolts are about $100.

Take an old truck to a diesel shop or dealership, and ask them to install a new head gasket kit ($400), ARP head studs ($650), new injectors ($2400), new injector hard lines ($650), new water pump ($125), new hoses and an endless list of "as long as we're in there" stuff, and of course at least $5k in labor - and you've made a bad decision regarding financial common sense - i.e. spending $10k+ on a truck that in even perfect condition is still only worth 10K. When faced with that reality, most thinkers will crush/part-out the truck and not spend a dime on it... We didn't even talk about brakes, ball joints, steering components, drivelines, tires, rust... and on and on and on...

Meanwhile, our performance 6.5TD Project ran without a problem to 300,000 miles in 7 years using TTY head bolts (till we sold it), and my 2001 GMC ran to 140,000 miles using TTY head bolts - even with the poorly designed factory crimped-style head gaskets. I get where the ARP stud advocates are coming from. I can actually read the engineering specs and understand the logic. This is partly why I installed ARP studs in my own 2001 GMC LB7 head gasket repair. I spent extra on this truck only because I did the work (and because I needed to say I did it, could photograph it and eventually write about it). It's just that at some point, people need to make a decision... Crush the truck or do what is necessary to save the truck without compromising basic service and dependability while not violating financial common sense. As part of an overall budget strategy, the lower cost TTY head bolts fit into that paradigm. Lil Red is getting TTY bolts.

What would mean most to me regarding this discussion about the value of studs/bolts is to study the actual service histories comparing engines built with studs/bolts along with a description of how the trucks were used, and then be able to discern some sort of recommendation from that. Right now, the stud advocates "say" they are better... We can read about tensile strength and a wide range of other stuff, but what's that mean in the real world to average truck owners?

My mistake. You had replied to a post from Robyn where she was writing about power levels in a 6.5 and I assumed your prices listed were for that engine.

[arveetek]

I watched an ARP video a while back where they discussed the "elastic" clamping load supplied by properly installed and torqued Series-2000 head studs produced for the Duramax. I like it that the ~$650 head studs have some elasticity designed-in.

However, we know that GM is still using TTY bolts in the newest L5P Duramax, which is rated for 445 hp / 910 lb-ft - and rated for up to a 35,000-lb GCVWR.

I interviewed the "Duramax Power Tour" team in 2000, who drove an LB7 equipped 3500-series truck towing a 20,000-lb event trailer. I rode in that truck as they wailed on it, on the I-90 continental divide pass just east of Butte, Montana. I asked them if they drove it like that all the time. I was told yes... They put in excess of 20,000 miles on that truck - hammer down all the time. I can also point to a 750,000-mile LLY Duramax used to commercial tow RV trailers all over North America, that I wrote about a few years ago. GM could acquire head studs equal to those offered by ARP (maybe even contract with them to provide) if they felt it was necessary.

I have a couple of debate points about studs that are hard to answer and difficult to challenge. 1- The aftermarket pushes anything that they can sell - ("while you're in there") type of stuff, including head studs. 2- Studs are simply easier to install than TTY bolts. You must mark the heads of each TTY bolt during the two angle tightening sequences or you'll mess up the installation. With studs, you only use a torque wrench. If you forget one or get out of sequence, it's really easy to check what the torque is for that stud. Personally, I think this is why many vendors/mechanics push studs (sell more expensive stuff and they are easier to install). Otherwise, they would/could point to actual durability tests involving direct comparisons between engines using head studs and TTY bolts (fleets would be the best source of information. Second best would be an accumulation of real-world reports from actual owners - like the story I did on the 751k mile LLY Duramax). For most, these head gaskets will wear out long before any real comparison can be done on the veracity of claims otherwise.

I have the opportunity to purchase some new ARP head studs for my 6.5L for the same cost as new TTY head bolts. Is there any reason NOT to use head studs in my application? This is a stock 6.5L with 375K on the clock and no other issues other than a blown head gasket. John Kennedy recommends studs.

Thanks,

Casey

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I have the opportunity to purchase some new ARP head studs for my 6.5L for the same cost as new TTY head bolts. Is there any reason NOT to use head studs in my application? This is a stock 6.5L with 375K on the clock and no other issues other than a blown head gasket. John Kennedy recommends studs.

Thanks,

Casey

I can easily make the case for TTY - which includes the quote you included in your post. What was not in that quote was the head gasket durability I saw with our 6.5TD Power Project, using TTY bolts (300K miles of mostly towing/performance miles without a single head gasket problem).

It's disappointing that "some" get perturbed when asked to provide support for their position. I don't understand it. If studs are better, state why you believe that... I have nothing to gain otherwise by promoting one type of fastener over another (I actually lost a vendor over this very issue). As an information resource (thedieselpage.com) I have more to gain by promoting the "best" option. There are several criteria for what could be considered "best". "Best" could defined as proven better - sorta like how the FDA approves new drugs (blind studies - direct comparisons). "Best" could be defined as being more than adequate for the vast majority of the owners while saving them a lot of money in the cost of fasteners. What's not "best" is theoretical or an arm chair opinion. I would ask the stud advocates to put some verifiable high mileage examples of head stud usage on the table to consider - like the following high mileage TTY head bolt example I talked about a couple of years ago - 772,470 miles, which backs up the story I did on the 751k C2500 Duramax RV hauler and our own 300k-mile 6.5TD Power project... Read more about high mileage Duramax trucks here: https://www.thedieselpageforums.com/...-March-updates



It used to be back in the early days of the 6.2/6.5 that GM's head gasket suppliers hadn't figured out how to design a gasket that worked for these engines. Far too many head gaskets failed in these engines because of poor gasket design, and that's when the aftermarket (and others) began advocating for studs for the 6.2L/6.5L. Then one day Fel-Pro designed the best head gasket, and head gasket failures almost disappeared. Turns out that the problem was never the fastener but the gasket design. But, old opinions die hard. By the way... throughout the early years of the 6.2L diesel engine production, GM used head bolts that were not TTY. They were simply torqued to a specified torque value in steps... like stud nuts are now. GM could have stayed with non-yielding head bolts, but they switched to TTY early and continued through to the end of their own production of this engine, and AMG continued to use TTY when they took over 6.5 production.

So, to answer your question.... because of their elastic head clamping design that compensates for thermal cycles and gasket compression (and my own verifiable long-term experience/success with them), I prefer TTY, especially for the 6.5. Now, for the Duramax, if cost is taken out of the equation, it's more of a toss-up in choice except perhaps for a high power (2x+) application, then ARP's engineering data "begins" to sway my opinion. But, even that is simply theoretical. ARP's own ad claims in the Northern Auto Parts catalog, when talking about diesel stud kits, say that their studs are preferred among "racing" enthusiasts. That said, I'm quite content in my choice of TTY for Lil Red's Duramax because it has been retired from any sort of racing/dyno/nitrous duty. The 6.5 I'm putting together right now will get Fel-Pro TTY head bolts along with Fel-Pro head gaskets... just like our 6.5TD Power Project did in 1999. Besides, due to the limitations in fuel delivery of the DS/DB fuel injection system, the 6.5 can't be made to produce a horsepower level that justifies studs... in my humble opinion.

Jim