THE IRON HORSE

LS3 your LY6

Chevy High Performance - - Contents - TEXT & PHO­TOS: Richard Hold­ener

LS3 your LY6

In case you haven’t been keep­ing up on cur­rent events, junk­yard LS en­gines are all the rage. You see, rather than spend big money to go out and build an en­gine, you can pull a com­plete run­ning one for pen­nies on the dol­lar. Ev­ery bit as im­por­tant is the fact that the com­plete en­gine comes with all the lit­tle nuts and bolts that can cause end­less hours of frustration and ex­pense when build­ing one from scratch. The most pop­u­lar junk­yard jewel is still the 5.3L, as it is both the most preva­lent and af­ford­able. Used in mil­lions of Chevy and GMC trucks, the ven­er­a­ble LM7, or other such 5.3L variant, has be­come the go-to swap en­gine for im­ports, turbo trucks, and early muscle cars. As good as the lit­tle 5.3L is, we had our heart set on some­thing a lit­tle big­ger. Af­ter all, big­ger re­ally is bet­ter.

Though the next step up the LS lad­der is the 5.7L, GM hasn’t pro­duced the LS1 for some time, and be­sides, we wanted the even big­ger 6.0L. Though the big­ger truck en­gines com­mand a pre­mium price, a 6.0L will al­ways make more power than a smaller 5.3L with equal parts. The ex­tra torque of­fered by a 6.0L will al­ways come in handy, es­pe­cially on a heavy ve­hi­cle.

Once we de­cided on a 6.0L we needed to hone in on the spe­cific ver­sion, as GM of­fered a va­ri­ety of dif­fer­ent 6.0L com­bi­na­tions over the years. The most com­mon ver­sion was the LQ4. Orig­i­nally equipped with iron LS heads (yep, that’s right), the LQ4 was quickly up­graded to alu­minum 317 heads in 2000. Used as the base 6.0L, the LQ4 fea­tured dished pis­tons, a mild cam (very mild in 1999-’00) and the 317 (cathe­dral port) heads. De­pend­ing on the ap­pli­ca­tion, the LQ4 was rated be­tween 300-325 hp and 360-380 lb-ft of torque. One step up from the LQ4 was the higher-com­pres­sion LQ9. The LQ9 was ba­si­cally an LQ4 with flat-top pis­tons and was rated at 345 hp and (oddly enough) an LQ4-match­ing 380 lb-ft of torque. What we had our eye on was a Gen IV LY6, and the rea­sons for this choice were nu­mer­ous.

The 2007-up LY6 6.0L fea­tured the Gen IV up­grades to the block and connecting rods, along with slightly higher com­pres­sion (9.6:1 vs. 9.4:1). What re­ally sealed the deal on the LY6

was the use of LS3-style rec­tan­gu­lar port heads. The 823 alu­minum heads of­fered peak flow num­bers of 317 cfm—a jump of over 65 cfm per run­ner com­pared to the 317 heads used on LQ4s and LQ9s. We like to think of the LY6 as a smaller, iron horse ver­sion of the all-alu­minum LS3.

Per­haps one of the big­gest up­grades to the LY6 com­pared to the LQ4 and LQ9 com­bi­na­tions was the use of Vari­able Valve Tim­ing, or VVT. The VVT mech­a­nism es­sen­tially ad­vanced and re­tarded the cam pro­file un­der dif­fer­ent driv­ing con­di­tions to im­prove things like idle, power, and drive­abil­ity, as well as re­duce emis­sions. Un­less you run the LY6 with a fac­tory ECU de­signed for use with VVT you will need to re­place the VVT cam with a con­ven­tional unit. This is the route we fig­ured most swap guys would take, and is ex­actly what we did on our LY6. To es­tab­lish a base­line be­fore up­grad­ing to LS3 sta­tus, we in­stalled a fixed LQ9 cam. This fac­tory cam pro­file was nearly iden­ti­cal to the

VVT cam, mi­nus the abil­ity to ad­vance and re­tard the cam tim­ing. We also re­placed the fac­tory drive-by-wire 90mm throt­tle body used on the LY6 with a man­ual 92mm unit. For both the LY6 and LS3 up­graded ver­sion, we re­lied on Hooker 1 7/8-inch long­tube head­ers, a Hol­ley HP ECU, and Meziere elec­tric wa­ter pump. Run in this con­fig­u­ra­tion, the LY6 pro­duced peak num­bers of 443 hp at 5,400 rpm and 467 lb-ft of torque at 4,500 rpm. Now it was time to LS3 our LY6. Since the LY6 al­ready fea­tured the rec­tan­gu­lar port 823 heads, all we needed to com­plete the LS3 trans­for­ma­tion was the LS3 cam and in­take man­i­fold. Truth be told, we com­pared the low-pro­file LS3 in­take to the LY6 (truck) in­take and there was al­most no dif­fer­ence in power be­tween the two. The LS3 in­take might be a bet­ter op­tion for tight hood-clear­ance ap­pli­ca­tions, but from a per­for­mance stand­point there was lit­tle to choose from be­tween the two. We swapped out the LQ9 cam (0.467/0.479-inch lift, 193/201-deg. du­ra­tion, 116 LSA) for the slightly more ag­gres­sive LS3 cam (0.551/0.525-inch lift, 204/211deg. du­ra­tion, 117 LSA). As luck would have it, the LY6 was fac­tory equipped with valvesprings that matched those found on the LS3 so no spring up­grade was nec­es­sary for the swap. The LS3 cam up­grade did re­quire the sin­gle-bolt cam gear and large cam-re­tain­ing bolt. The cam swap was com­bined with the low­pro­file LS3 in­take. Once up­graded, the LS3-cammed LY6 pro­duced peak num­bers of 475 hp at 5,800 rpm and 469 lb-ft of torque at 4,600 rpm. Ba­si­cally, the LS3 cam was worth over 30 hp mea­sured peak to peak, and more than 50 hp at 6,400 rpm. The iron horse LY6 was now ready for some boost, nitrous, or even more ag­gres­sive cam tim­ing. CHP

01 | The 6.0L LY6 is good, but with help from parts meant for an LS3 it can be even bet­ter!

03 | For our dyno test, we headed over to Westech Per­for­mance in Mira Loma, Cal­i­for­nia, where we first had to re­place the VVT cam and front cover assem­bly with a con­ven­tional cam and cover.

02 | The 2008 LY6 fea­tured an iron block, alu­minum rec­tan­gu­lar port 823 heads, and VVT cam op­er­a­tion.

05 | We re­placed the VVT cam assem­bly with an LQ9 three-bolt cam. This cam shared specs with the VVT cam, mi­nus the ad­justa­bil­ity.

04 | Off came the dam­per and front cover to al­low ac­cess to the sin­gle-bolt cam gear.

07 | The LY6 was equipped with a rec­tan­gu­lar port truck in­take de­signed to ac­cept the fac­tory drive-by-wire 90mm (mea­sured at 87mm) throt­tle body. We re­lied on a FAST 92mm throt­tle body for both the LY6 and LS3 in­takes.

06 | The cam swap re­quired a new front cover. Ours came from a GM block com­ple­tion kit sup­plied by Gan­drud Chevro­let. The front cover in­cluded the gas­ket, bolts, and cam po­si­tion sen­sor.

19 | Run on the dyno af­ter the LS3 up­grade, the mod­i­fied LY6 now pro­duced 475 hp at 5,800 rpm and 469 lb-ft of torque at 4,600 rpm.

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