O-RINGS VS. STUDS
QUESTION: I have an ’06 Dodge Ram 2500 with a 5.9L engine. I purchased and plan to install the revised ATS Diesel Performance Aurora 3000/Aurora 5000 compound-turbocharger kit with external wastegate. I have already installed Mads Smarty BBI Stage 1 injectors, a Hamilton Camshafts 178/208 cam with valvesprings and pushrods, and other supporting fuel mods. I also had ARP 625 cylinder-head studs put in and the head milled for flatness.
I read the Diesel Power article on O-ringing and your answers to tech questions regarding O-rings. While I don’t disagree that the modification helps (when done correctly), your recommending O-rings for boost pressure above 40 psi seems to conflict with your own advice. Most Diesel Power articles I’ve read typically have only recommended head studs for larger single or mild compound-turbo setups. The ATS website says, “When boost levels are more than 48 psi, head studs are highly recommended.” There is no mention of needing O-rings. Many online forum posts show plenty of engines making 60 psi and 600-plus hp using head studs only. The article in your July 2018 issue mentions the engine had 200,000 miles on it when the head studs were installed but doesn’t say whether the head was checked for flatness or milled. If the head had been milled, would studs only be perfectly fine?
Regarding requirements for clamping the head, is there more that has to be factored in, such as head flatness, drive pressure, injection timing, and such? It would be nice to see an article that discusses the variety of root causes that can lead to head-gasket failures and when the variety of head mods are required. Also, are there any drawbacks to O-ringing? I know the issue with fire rings and heat cycles, but can
O-rings have a similar issue? Does the head have to be retorqued? What about trucks that are subjected to very cold winter temperatures? Brian Lumppio
ANSWER: We sat down with Bill Allen, manager of Source Automotive and NHDRA competitor who did our O-ring work, and asked his advice regarding newer Cummins engines. “We would not O-ring the ’06 Dodge Ram 2500’s head. Under 40 psi of boost, from our own experiences, the second-generation trucks are the ones that benefit most from the O-ring addition. The newer engines have a multi-layered-steel gasket that does not include a fire ring around the cylinder (as were found in the ’94-to
’02 composite-style gaskets). The head we O-ringed was completely rebuilt and checked after the head-gasket failure. Prior to that, the gasket was replaced, but the head was not checked for flatness, as the owner was trying to save some money on the build. Would studs alone be fine? Not in my experience, especially with younger enthusiasts starting to purchase these trucks, and their unawareness of how to properly handle warm-up and such with a high-powered Cummins. I would always err on the side of more protection than none when it comes to the expense of losing a head gasket. Head flatness, injection timing, coolant pressures, and drive pressures all effect head-gasket longevity. Any issues with one or more of those can cause a failure. O-rings do not have the same heat-cycle failures as the fire rings do. We currently have a local customer with a ’95 Dodge Ram 2500 that makes more than 525 hp. The engine has been compounded and O-ringed since January 2011. He drives it daily for personal and work use, and to date he has experienced zero head failures. The head has been retorqued three times since initial head installation, and now we only see that truck for normal maintenance. Procedure for cold winter temperatures is the same as mild: Let the engine warm up before ripping out high boost numbers. Our rule of thumb is nothing over 20 psi of boost until we see a full thermostat cycle.”
At less than 40 psi of boost, second-generation Cummins engines benefit from having the cylinder head O-ringed because their composite-style head gasket includes a fire ring around each cylinder. The multi-layered-steel head gaskets on later models can withstand higher boost without O-ringing the head.