Cir­cle of Con­fi­dence

Adding O-rings helps keep the cylin­der head down and val­ve­train happy when boost pres­sures in­crease

Diesel Power - - Contents - Words by BRUCE W. SMITH + Photos by BRUCE W. SMITH

NOTH­ING BEATS the feel­ing of rolling a Dodge Ram pickup with a freshly com­pound-tur­bocharged Cum­mins diesel engine out of the shop and onto the street for the first time and ex­pe­ri­enc­ing the re­ward for the hours and dol­lars in­vested to gain a big bump in power. After mak­ing a few easy loops to get ev­ery­thing warmed up prop­erly, you fi­nally mat the throt­tle and feel all the torque come alive as the com­pounds do what they were de­signed to.

Ev­ery­thing hap­pens si­mul­ta­ne­ously: The nee­dle on the boost gauge rises to 20 psi and sud­denly whips north of 40 psi as the tur­bos work their magic. Tires smoke. The ex­haust cleans up. You’re pushed into the seat. Yes, ev­ery­thing is work­ing bet­ter than you imag­ined. What a rush!

How­ever, just when you think you’re now all set with brute power at your dis­posal any time your right foot is mat­ted, boost

sud­denly falls and white smoke starts pour­ing from the tailpipe. The power is gone as quickly as it be­gan, and the acidic smell of burn­ing rub­ber fill­ing the cab is re­placed by the heart­break­ing odor of hot oil and an­tifreeze com­ing from places it shouldn’t. Your rig’s com­pounded Cum­mins just blew the cylin­der-head gas­ket—or worse.

“We’ve seen a num­ber of cus­tomers come through here over the years who have in­stalled their own com­pound tur­bos and ended up hav­ing head gas­ket is­sues,” says Bill Allen, gen­eral man­ager of Source Au­to­mo­tive, an Ore­gon-based dieselper­for­mance shop that spe­cial­izes ex­clu­sively in Cum­mins. “They in­stall ARP head studs and bolt on the tur­bos think­ing all is well. Then they find out studs alone aren’t enough to hold the gas­ket in place when those boost pres­sures head north of 40 psi.”

While high-qual­ity head studs add a needed level of engine dura­bil­ity, those who hot-rod 24-valve en­gines with com­pound tur­bos need to con­cen­trate on tak­ing mea­sures on the head it­self when boost pres­sures head north of 40 psi. If you don’t, head-gas­ket fail­ure is guar­an­teed. That was the sit­u­a­tion we found our­selves in with our Ford F-250 “Fum­mins.”

Our project rig’s sal­vage-yard ’00 5.9L pow­er­plant had more than 200,000 miles on it be­fore it was dropped into our Su­per Duty’s engine bay. Since we were on a tight bud­get, only ba­sic up­grades were done. It was cleaned up ex­ter­nally, ARP head studs re­placed the fac­tory bolts, and we ran it on an engine stand to make sure all was good be­fore per­form­ing the trans­plant.

It held to­gether with the big sin­gle turbo. But when the com­pounds were added, the head gas­ket blew out after the third hard pull on the dyno (about the same time the nee­dle on the boost gauge flew past 40 psi). The ex­pen­sive les­son we learned is that if you’re go­ing to put com­pounds on any diesel, it’s im­per­a­tive the head be pre­pared ac­cord­ingly. Tight bud­get or not, this means hav­ing the head re­built and

O-ringed to ac­com­mo­date in­creased boost pres­sures. If the engine is out of the truck, the block should be ad­dressed as well.

Prepping a used 24-valve 5.9L or 6.7L Cum­mins head for com­pound tur­bos in­volves sur­fac­ing the head, re­plac­ing valve guides, and clean­ing the seats, as well as up­grad­ing valves, seals, and springs. Once all of this is done, then the head is O-ringed.

We turned to Bear­ing Ser­vice Com­pany in Port­land, Ore­gon, an ex­pert diesel-engine ma­chine shop, for the re­build por­tion. Owner Brian Schut­zler says his com­pany has spe­cial­ized in engine re­build­ing since 1929, and all the work is cus­tom. They don’t cut corners when it comes to mak­ing sure the work is done with tight tol­er­ances and ex­treme at­ten­tion to ev­ery de­tail.

BSC’s work on our Cum­mins cast­ing af­firms this ethic. After Brian cleaned, Mag­nafluxed, and resur­faced the head (which was slightly warped and prob­a­bly the cause of the ini­tial gas­ket fail­ure), tech­ni­cian Ja­cob Por­tillo han­dled the re­build. In­take and ex­haust valves were re­placed with higher-qual­ity ver­sions, which Ja­cob trued be­fore in­stal­la­tion. “We do that to en­sure they are per­fect be­fore assem­bly, be­cause mass-pro­duced valves can have some wob­ble. We take .001 to .002 inch off the face to make sure they are true,” the vet­eran ma­chin­ist says.

Ja­cob also pays spe­cial at­ten­tion to valve heights, clean­ing out the oil-re­turn pas­sage and the in­jec­tor hold-down thread holes so there are no is­sues dur­ing re­assem­bly. He also checked our set of Moun­tain High Per­for­mance cryo’d 125-pound spring pres­sure rates and heights. “This is just your ba­sic diesel head re­build,” Brian says. “It’s noth­ing re­ally spe­cial. We do a lot more ex­otic stuff when it comes to build­ing an engine for sled pulling or drag rac­ing.”

The two big­gest up­grades done to our head were re­plac­ing the orig­i­nal valvesprings with 125-pound Moun­tain High Per­for­mance pieces and re­plac­ing all the valve stem seals

with S.B. In­ter­na­tional’s Vi­ton seals.

“On a head for any com­pound-tur­bocharged Cum­mins, we in­stall tophat–style seals be­cause the valvespring it­self holds them in po­si­tion and will not al­low the seal to fail from higher com­bus­tion tem­per­a­ture and boost val­ues,” Bill says.

“We use the green ex­haust ma­te­rial on our seals specif­i­cally for the higher tem­per­a­ture rat­ing of high-horse­power diesel en­gines. As for the cryo-treated valvesprings with the in­creased seat pres­sure, again, we want to elim­i­nate pos­si­ble valve float or bind un­der the higher rpm and boost pres­sure own­ers see with the com­pounds.”

Source Au­to­mo­tive’s lead diesel tech­ni­cian Robert Gates han­dled the O-ring pro­ce­dure us­ing BHJ Prod­ucts’ spe­cial Oring reg­is­ter plate and cut­ter kit. The cut­ter is a crank-style, hand-op­er­ated de­vice that at­taches to a jig that is torqued atop the head. Both tools are pre­ci­sion-ma­chined, with tol­er­ances greater than .001 inch.

The O-ring­ing process is quite sim­ple: A groove that’s aligned with the head gas­ket’s fire ring is cut in the face of the head, and then a stain­less steel wire is in­serted in the groove. But cut­ting grooves to the ex­act depth that’s nec­es­sary and de­cid­ing how much the wire pro­trudes above the fire deck is any­thing but sim­ple. Ex­pe­ri­ence plays a huge role in such fac­tors.

BHJ of­fers a wide ar­ray of jigs and spe­cial heat-treated stain­less wire for O-ring­ing diesel cylin­der heads. BHJ’s Chris Ouel­lette says, “We tell Cum­mins cus­tomers they should get per­fect re­sults us­ing .041-inch wire in .039-inch grooves and let them go their own way from there. We do rec­om­mend a pro­tru­sion of .006 inch (+/- .001 inch) for MLS gas­kets and .011 inch (+/- .001 inch) for com­pos­ite Cum­mins B gas­kets.”

Bill’s ap­proach to O-ring­ing—step up one size, us­ing .048-inch grooves set at a depth of .040 inch to hold .051-inch wire—stems from hav­ing more than a decade of ex­pe­ri­ence in both build­ing and rac­ing 1,000-plushorse­power, street-strip diesel rigs. This size groove sup­ports a pro­tru­sion of .011 inch above the fire deck, so the wire bites into the fire ring with­out cut­ting so deeply that it af­fects the gas­ket’s struc­tural in­tegrity. Source Au­to­mo­tive says it has never ex­pe­ri­enced a gas­ket fail­ure us­ing that O-ring pack­age on en­gines tak­ing in more than 70 psi of boost.

8. Our 5.9L head re­ceived a set of cryo­genic-treated 125-pound valvesprings from Moun­tain High Per­for­mance. The stronger springs are said to keep the valves from float­ing or stick­ing un­der high boost pres­sures (40 to 75 psi) and engine speed north of...

6. Ev­ery diesel head and block that runs through Bear­ing Ser­vice Com­pany gets a thor­ough clean­ing and Mag­naflux­ing. They are fur­ther cleaned with spe­cial brushes dur­ing the en­su­ing re­build­ing process to en­sure oil gal­leys and pas­sages are de­bris-free....

7. Ja­cob mea­sures ev­ery as­pect of the head, mak­ing notes on a build sheet. Here he checks in­take-valve heights, which are kept to .038 inch as per Cum­mins spec­i­fi­ca­tions (.035 to .038 inch).

1. Set­ting the heat-treated stain­less steel wire into the O-ring groove around a 24-valve cylin­der head re­quires pre­ci­sion work­man­ship and great at­ten­tion to de­tail.

4. Ja­cob Por­tillo, lead ma­chin­ist at Bear­ing Ser­vice Com­pany, re­built our project’s head, which in­cluded the three­step process of refac­ing the valve seats. 5. Ja­cob takes the ex­tra step of touch­ing up brand-new valves to en­sure they are per­fect be­fore...

3. This is the re­sult of a stock Cum­mins cylin­der head be­ing sub­jected to 45 psi of boost from com­pound tur­bocharg­ers. The blown head gas­ket could have been avoided if the head had been sur­faced and O-ringed prior to the tur­bos be­ing in­stalled.

2. In­stalling a spe­cial stain­less steel wire (O-ring) locked in a groove that matches up with the fire ring of each cylin­der of a stock Cum­mins head gas­ket will en­sure good re­li­a­bil­ity for en­gines run­ning 40 to 75 psi of boost.

Source Au­to­mo­tive’s lead tech­ni­cian Robert Gates uses old-fash­ioned mus­cle power to op­er­ate a BHJ Prod­ucts cut­ting tool while in­stalling O-rings on a 24-valve 5.9L Cum­mins cylin­der head.

13. The cut­ter is placed into the hole in the reg­is­ter plate and then locked down us­ing four hand-tight­ened screws. Depth of the cut (down to .0005 inch) is ad­justed by turn­ing the click-stop wheels un­der the han­dle at the top of the head. 14. No...

11. Our newly re­built Cum­mins head was taken to Source Au­to­mo­tive, where lead tech­ni­cian Robert Gates per­forms O-ring in­stal­la­tions. Here, he po­si­tions the dow­els to align the BHJ reg­is­ter plate with the head. The plate is then torqued down to 50 ft-lb...

12. The pre­ci­sion-made BHJ O-ring cut­ter has a tri­an­gu­lar-shaped head with three car­bide cut­ting blades. When one blade wears down, the head can be quickly ro­tated to the next one.

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