Diesel World – October 2019

Usingcompressedairandwitha custom-madeadapterinplaceofthethermostat,the

leak-downtestbegins.Again,thisis anotherwaythatthefolksatFleecedouble-check

alloftheirwork.Thistestis performedbeforetheheadmovesontoitsfinalstagesof

assembly.

WiththeManleyvalvesandfreshMahlevalvestemsealsinplace,it’stimetoinstall

theHamilton103-lbsprings.Withtheretainersarrangedonthesprings,a valvespring

compressortool(alsofromHamiltonCams)is usedtocontractthespringsenoughto

installnewOEMCumminslocks.

HamiltonCams’103-lbvalvespringsforthe24-valveCumminsareextremelypopular

intheaftermarket,andFleeceinstallsthemineveryPerformanceheadfora reason.

Theyprovidea 103-poundseatpressure(vs.78-to82-lbsstock),butmoreimportantlya

nosepressureof180-lb.Somecompetingmanufacturersofferspringswithhighernose

pressure,whichtendstoshortencamshaftlife,sometimessignificantly.

ToolsteelvalvespringretainerscomestandardwithHamilton’s103-lbspringsineach

Performancehead.Thetoolsteelunitsaremorethansufficientformostapplications—

mostapplicationsbeingenginesoperatingatorbelow4,500rpm—orwitha stockto

moderatecamshaftupgrade.

StainlessintakeandexhaustvalvescomestandardineveryPerformanceserieshead.

ManufacturedbyManleyPerformanceProducts,theyfeaturethickchromevalvestems,

hardtips,anda headdiameterof1.380-incheson6.7Lheads(vs.1.300-inchesstock).On

5.9LversionsofthePerformancehead,1.300-inchManleyvalvesareemployed.

Aftermakingitswayoutofthepaintbooth(whichtakesplacebeforethevalves,valvesprings,retainers,andlocksareinstalled),thefinishedproductcomesoutlookinglikethis.

Thankstothe5-anglevalvejobandlargervalves,CumminsownersthatoptforFleece’sPerformanceheadtypicallysee3 to5 psilesspeakboostpressure.Thisis a testamenttothe

head’simprovedflowandefficiency.Asa bonus,makingthesamepowerwithlessboostinthemix,it’salwayseasierontheengine.

TECH COMPETITION-READY, OFF-THE-SHELF AVAILABILITY

82 OCTOBER I 2019 • DIESEL WORLD http://www.dieselworldmag.com