I’m wondering why the hell this little 4cyl has head studs that cost as much as the big v8s?

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I’ve decided not to do the head studs for the moment. My tune is relatively mild and I’ve been enlightened a little as to why the oem use tty bolts and i now know there are reasons they do and down sides to rigid studs.

These studs are cheap! You should price out the ARP 625 studs I use at work in all my Cummins builds... then get back too me!


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And what exactly are the "downsides" to studs? The factory uses TTY bolts because they can be installed by a machine that doesn't need a torque sensor requring constant calibrations, the stepper motors can be set for a certain angle and it will always hit that angle on every install.

HOWEVER in operation on this engine, the heat cycling WILL cause the factory bolts to either weaken or back out (same result) and lose clamping force, and the 2500+ psi of combustion pressure will push out through the layers of head gasket and into the water jacket, pushing the coolant out through the overflow port. Low coolant alarms are the first indication of this leak, and once it has happened (and it will) the soot from combustion will also travel into that gap between the gasket layers and holds it open - allowing the coolant to migrate back into the cylinders when the engine is off (pressure in the coolant system but not in the engine) and resulting in oil contamination.

The studs resolve ALL of these issues. After working on over 110 engines, most of which have gotten the studs (anything that received more of my services than just a basic timing belt) NOT ONE has come back reporting a reoccurance of the leak. NOT ONE has reported any downside to having the studs in the engine. Many hundreds more engines have had studs installed by their owners, and I have again not heard of a single engine with any negative report of any kind about use of studs.

I was not involved with the engineering discussions around development of the stud kit when it was originally conceived and worked out with ARP, only coming on board as the first installer and reporting findings back to the original member who developed the upgrade. The factory clamping force is about 17,000 PSI, the studs as we are using them are putting down about 19,000 psi and are (from ARP) at about 75% of their elastic range for the fastener. WELL WITHIN the capabilities of the materials.

You’ve put 100 sets of studs in? That’s a lot of head gaskets. How many were this engine or what engines?

I've worked on over 110 CRDs - this is the ONLY vehicle I work on professionally. Not all of those were head gasket jobs, some were just a timing belt and some were studs / rockers / glow plugs (installing the studs one at a time). The studs can be installed without removing the head IF the engine passes the cold test and doesn't have a head gasket leak YET. But once the leak presents itself, you have to do the gasket too, the studs won't close up that gap.

I figure I've installed probably around 80 sets of studs now, and of that, probably around half have been with a head gasket and valves too. There have been a lot of valve jobs.

NOT ONE has come back with a head gasket leak or a subsequent valve failure after the valves have been replaced. If the engine is closing in on 200k miles, it REALLY doesn't make sense to skip doing the valves, b/c they have proven themselves to be a design weakness that is far more than a statistical blip. Yeah it's more work and parts... But when it is done, if all the upgrades are done at the same time, the engine is bulletproof for the life of the truck. That's saying something.

Why don’t you just save us all a little time and tell us since you clearly want to.

https://www.dieselpowerproducts.com/p-4824-arp-ca625-diesel-head-stud-kit-985-18-59l67l-dodge-cummins-247-4204.aspx


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geordi,
Have you any customers that have done over 200,000 miles on replaced valves?
I am wondering if replacing the valves makes the problem go away or will it be an ongoing issue with high mileage CRD's.

the kJ crd is a relatively cheap diesel to build on, do arp head studs and upgraded valves and arp connecting rod studs and ceramic coat the head and valves and pistons and exhaust manifold and have fun that’s my recipe I am building in my spare time to drop in my dd... you can’t spell the word diesel or performance without a few dollar signs


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I've worked on over 110 CRDs - this is the ONLY vehicle I work on professionally. Not all of those were head gasket jobs, some were just a timing belt and some were studs / rockers / glow plugs (installing the studs one at a time). The studs can be installed without removing the head IF the engine passes the cold test and doesn't have a head gasket leak YET. But once the leak presents itself, you have to do the gasket too, the studs won't close up that gap.

I figure I've installed probably around 80 sets of studs now, and of that, probably around half have been with a head gasket and valves too. There have been a lot of valve jobs.

NOT ONE has come back with a head gasket leak or a subsequent valve failure after the valves have been replaced. If the engine is closing in on 200k miles, it REALLY doesn't make sense to skip doing the valves, b/c they have proven themselves to be a design weakness that is far more than a statistical blip. Yeah it's more work and parts... But when it is done, if all the upgrades are done at the same time, the engine is bulletproof for the life of the truck. That's saying something.

...and upgraded valves and arp connecting rod studs and ceramic coat the head and valves and pistons and exhaust manifold and...