O-RINGS VS. STUDS

Diesel Power - - Top Tech Questions -

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

via email

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.

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