The Big Bang 6.0L Gen 4: Big Boost

Big-Boost Edi­tion

Hot Rod - - Contents - Richard Hold­ener

hBy now, ev­ery LS owner should be fa­mil­iar with at least one of the Big Bang LS en­gines. To re­fresh your mem­ory, we kicked off the Big Bang test­ing at HOT ROD in 2011, when we took a stock LR4 4.8L short-block (that we orig­i­nally thought was a 5.3L) and treated it to sur­fac­ing and a light ball hone, and in­creased the ring gap on the orig­i­nal stock rings. Then we added ported heads, a cam up­grade, and a new in­take man­i­fold. Af­ter pump­ing boost through the com­bi­na­tion with a pair of tur­bos, we even­tu­ally pro­duced more than 1,200 hp, and the thing was still alive!

We re­peated this pro­ce­dure with a larger 5.3L for Truckin mag­a­zine, then again with a 6.0L for Su­per Chevy. The 5.3L topped the 1,300hp mark, while the larger 6.0L thumped out 1,482 hp at 28.5 psi of boost. The one thing this trio of LS en­gines had in com­mon was they were all early Gen 3 ver­sions. When

GM in­tro­duced the Gen 4, the up­graded ver­sion in­cluded a re­vised block and stronger (full-float­ing) con­nect­ing rods. Since the rods were the even­tual weak link in the LS, we de­cided it was high time to ap­ply the Big Bang treat­ment to a Gen 4 en­gine.

The idea be­hind the Big Bang test­ing was pretty sim­ple: We wanted to il­lus­trate how much power the stock in­ter­nals could with­stand. Un­der­stand that just be­cause the en­gine will throw down a huge power num­ber for one dyno pull doesn’t mean it will do that all day—or even twice, for that mat­ter. As you in­crease the power out­put, you de­crease the life cy­cle of the com­po­nents. Run­ning at 350 hp, the en­gine will prob­a­bly last 250,000 miles or longer. Run at 1,482 hp, the rods in the Gen 3 6.0L only lasted one run. The stock com­po­nents were de­signed for the in­tended com­bi­na­tion of power out­put and longevity. Rac­ers have run these stock, bot­tom-end LS en­gines near the 1,000-fly­wheel-horse­power level for many passes. As you in­crease power, the num­ber of po­ten­tial (suc­cess­ful) runs de­creases, and who wants to oil down a track or drive over their own crank at 150 mph? The point is, the big num­ber does not mean you can go out and run it like that. These Big Bang en­gine tests were just ex­er­cises we did to find the break­ing point, which we failed at (but more on that later).

For years, many LS en­thu­si­asts scoffed at the 6.0L due to its larger bore. Their con­cerns in­cluded re­duced head-gas­ket seal­ing and thin­ner cylin­der-wall thick­ness, at least com­pared with the smaller 5.3L. Test­ing on the pre­vi­ous Gen 3 6.0L sure seemed to in­di­cate that nei­ther of these were a prob­lem, as the con­nect­ing rod let go well be­fore we ex­pe­ri­enced any is­sues with gas­ket seal­ing or wall in­tegrity. Of course, the 6.0L is more ex­pen­sive and harder to find than the

5.3L, so we sus­pect those are the ma­jor rea­sons for the con­tin­ued pop­u­lar­ity of the smaller en­gine. If you can get to the de­sired power goal with a 5.3, why go to the ex­pense of the big-bore ver­sion, right? This is es­pe­cially true of com­bi­na­tions look­ing for any­thing less than max­i­mum power. Prop­erly tuned, a tur­bocharged 5.3 LM7 (or other vari­ant) can ex­ceed 1,000 hp for race ap­pli­ca­tions, or it can be used to tow a trailer at lower boost lev­els—such is the flex­i­bil­ity of a turbo en­gine. A 6.0, how­ever, will make more power at any given boost level and im­prove spool-up, some­thing im­por­tant when run­ning a larger turbo(s).

The Gen 4 6.0L cho­sen for this test was a 2008 LY6. This par­tic­u­lar ver­sion had a num­ber of de­sir­able fea­tures, in­clud­ing rec­tan­gle-port 823 (LS3style) heads, a free-flow­ing in­take, and vari­able valve tim­ing (VVT). Se­cured on­line from LKQ, the high-mileage LY6 was well-worn and used for nu­mer­ous

com­par­i­son tests be­fore be­ing drafted into Big Bang duty. Prior to run­ning, the LY6 short-block was dis­as­sem­bled and treated to sur­fac­ing, a quickie ball hone, and a fresh coat of paint. The real rea­son for the dis­as­sem­bly was to in­crease the fac­tory ring gap on the orig­i­nal pis­ton rings. In most cases, pis­ton fail­ure un­der pres­sure is caused by in­suf­fi­cient ring gap. The rings heat up and the ends butt to­gether and seize mo­men­tar­ily in the bore. The re­sult is a bro­ken ring land on the pis­ton, but the cul­prit is ac­tu­ally in­suf­fi­cient ring gap. For our LY6, the ring gap was in­creased from a mea­sured 0.019/0.024 inch to a lit­tle more than 0.030 inch for both top and bot­tom rings. The orig­i­nal rod bolts were also re­tained, as were the pro­duc­tion lifters, but we swapped out the VVT tim­ing setup for a 4X cam gear and a used chain.

Though we re­tained the stock ro­tat­ing as­sem­bly, we made changes to the cam and top end. To en­sure plenty of power, we se­cured a Lil John’s Mo­tor­sport So­lu­tions Stage 3 twin-turbo cam from Brian Too­ley Rac­ing. This cam was a sig­nif­i­cant step up the per­for­mance lad­der com­pared with the stock LY6 cam and of­fered 231/243 de­grees of du­ra­tion at 0.050-inch tap­pet lift, 0.605/0.614-inch valve lift, and 115+5-de­gree lobe-sep­a­ra­tion an­gle.

The cam was teamed with a set of CNC­ported Trick Flow Spe­cial­ties Gen X 225 heads. Why re­place the fac­tory rec-port LS3 heads with cathe­dral-ports, you ask? Tested on the nor­mally as­pi­rated 6.0L, these Gen X 225 heads were worth 30 hp more than the stock rec-port heads. More power nat­u­rally as­pi­rated (NA) equals more power un­der boost!

The heads were se­cured us­ing GM LS9 head gas­kets and ARP 625 head studs. Top­ping it off was a Hol­ley Race Sniper in­take. De­signed for boosted ap­pli­ca­tions, the heavy-duty in­take is ca­pa­ble of with­stand­ing more boost than the stock bot­tom-end ever could, with rac­ers re­port­edly run­ning as much as 40 psi. The short­run­ner Race Sniper was also cho­sen to help re­duce midrange torque pro­duc­tion, some­thing that re­ally takes a toll on the cast in­ter­nals. The Race Sniper was teamed with a match­ing 92mm Sniper throt­tle-body and 120-pound Hol­ley in­jec­tors fed by an Aero­mo­tive pump, which was fur­ther aug­mented by a 17-volt Kenne Bell Boost-aPump. Dial­ing in the all-im­por­tant air/fuel and tim­ing curves was a Hol­ley HP ECU with a 3-bar MAP sen­sor.

With our en­gine at the ready, we in­stalled it on the dyno at Westech Per­for­mance Group to estab­lish a base­line in NA trim. The 6.0L did not dis­ap­point us, generating peak num­bers of 548 hp at 7,000 rpm and 462 lb-ft of torque at 5,500 rpm. Sat­is­fied with our start­ing point, it was time for boost.

For this test, we du­pli­cated the twin-turbo sys­tem run on the pre­vi­ous Gen 3 6.0L. The stain­less turbo head­ers from DNA Mo­tor­ing fed ex­haust to a pair of S475 BorgWarner tur­bocharg­ers sup­plied by LJMS. Orig­i­nally equipped with larger T6 ex­haust hous­ings, we re­placed them with smaller T4s for this ap­pli­ca­tion. Each S475 fea­tured a cast im­peller wheel, an 83mm tur­bine, and a 1.0 A/R. The tur­bos were cho­sen not only be­cause they were ide­ally sized for maxi-

mum spool-up on our 6.0L but be­cause they could sup­port 1,000 hp each—more than enough for our stock bot­tom-end test. Con­trol­ling the boost was a pair of Hyper­gate45 waste­gates from Tur­boS­mart. We also com­bined dif­fer­ent springs and a man­ual waste­gate con­troller to reach our even­tual ceil­ing of 29.2 psi. Cool­ing the heated charge temp was a dual-core, air-to-wa­ter in­ter­cooler from CXRac­ing. Run with ice wa­ter, the core dropped in­let air temps by a good 200 de­grees.

Af­ter run­ning the Gen 4 6.0L in NA trim, we ap­plied boost grad­u­ally, al­low­ing us to dial in the tune. Since boost is the great mul­ti­plier, it doesn’t take much for a 548hp en­gine to start mak­ing some se­ri­ous power. Run at 14.4 psi, the twin-turbo 6.0L pro­duced 1,078 hp, while 16.0 psi upped the ante to 1,150 hp. Crank­ing up the boost knob to 17.5 psi al­lowed us to eclipse the 1,200hp mark, with a peak of 1,213 hp, but big things started to hap­pen be­yond 20 psi. Run­ning 22 psi, the 6.0L pro­duced 1,349 hp, but 26.6 psi put us at 1,433 hp. We were just be­low the power out­put of the pre­vi­ous Gen 3 6.0L, which broke at 1,482 hp. This is when we started to worry whether this Gen 4 en­gine had enough in re­serve to eclipse the Gen 3. An­other tickle on the old power knob brought the boost to 29.2 psi, where the 3-bar MAP sen­sor called it quits. We are happy to re­port that the MAP sen­sor gave up the ghost at the top of the rev range and al­lowed us to make a full pull to the tune of 1,543 hp and 1,256 lb-ft of torque. Imag­ine that: an en­gine orig­i­nally de­signed by GM to pro­duce ap­prox­i­mately 400 hp was now mak­ing close to four times that amount.

It is safe to say the Gen 4 rods are stronger than the Gen 3 ver­sions, and that these dang LS en­gines never cease to amaze us.

01] This Big Bang ad­ven­ture started with a 2008 LY6 en­gine. Out came the stock pis­tons to al­low ac­cess to the fac­tory rings. Note the dual valve re­liefs em­ployed on this VVT ap­pli­ca­tion.02] The key to run­ning big boost on a stock bot­tom-end is in­creas­ing the ring gap. We mea­sured the fac­tory ring gaps on the high­mileage pis­tons af­ter re­moval. The stock rings checked in at 0.019 inch (top) and 0.024 inch (bot­tom). These same rings were then re-gapped with a go/no-go min­i­mum of 0.030 inch. We gapped the rings us­ing this trick ring-gap­ping tool from To­tal Seal.03] The block was sur­faced to en­sure proper seal­ing un­der boost, then given a quickie ball hone and a fresh coat of black paint. The orig­i­nal stock LY6 crank was then re­in­stalled.04] The Gen 4 en­gines come with stronger con­nect­ing rods rel­a­tive to the pre­vi­ous de­sign. We torqued the rods ac­cord­ing to the fac­tory specs us­ing the orig­i­nal, high­mileage bolts.

01] Be­fore adding boost, we ran the 6.0L in NA trim. Equipped with the turbo cam and Sniper in­take, the TFS heads and Stage 3 cam pro­pelled our 6.0L to 548 hp at 7,100 rpm and 462 lb-ft of torque at 5,500 rpm.02] Straight from the pre­vi­ous Gen 3Big Bang 6.0L, we reused the S475 BorgWarner tur­bos from Lil John’s Mo­tor­sport So­lu­tions. Since they can sup­port nearly 1,000 hp each, there was more than enough boost for the Gen 4 party.03] The bounty of boost was fed through this dual-core, air-to-wa­ter in­ter­cooler from CXRac­ing. We feared that we may have been get­ting near the flow and cool­ing lim­its of this in­ex­pen­sive cooler, but it fit and worked well on our pre­vi­ous Big Bang test en­gines.04] Con­trol­ling boost was a pair of 45mm Hyper­gate waste­gates from Tur­boS­mart. Our even­tual spring com­bi­na­tion pro­vided a min­i­mum boost of 14.4 psi, which we raised with a man­ual boost con­troller to a max­i­mum of 29.2 psi.

01] Tur­boS­mart also sup­plied a Race Port blow-off valve to elim­i­nate the pres­sure spike that oc­curs un­der lift-throt­tle con­di­tions.02] We ran the turbo com­bi­na­tion with a 92mm Hol­ley Sniper throt­tle-body. Throt­tle­body siz­ing is less crit­i­cal on turbo ap­pli­ca­tions, as rac­ers have made much more power breath­ing through a 92mm open­ing.03] Use of the stain­less-steel turbo head­ers from DNA re­quired some creative work with plug wires. We ran these Ac­cel wires with ce­ramic boots where we could, but Westech’s Troy Goldie also whipped up a few ex­tra-long plug wires to wrap un­der the head­ers.04] Us­ing Hol­ley’s HP ECU, we di­aled in the 120-pound Hol­ley in­jec­tors at each suc­ces­sive boost level. Start­ing at 14.4 psi, the 6.0L pro­duced 1,078 hp, while 16.0 psi brought 1,150 hp and 1,213 hp at 17.5 psi. Pump­ing things up to 22 psi al­lowed the 6.0L to ex­ceed the 1,300hp mark, with a peak of 1,349 hp. The next step up in boost to 26.6 psi un­earthed al­most 100 hp, with the power nee­dle now reg­is­ter­ing 1,433 hp. The fi­nal run of the day (where we maxed out the 3-bar MAP sen­sor) crushed the 1,482hp mark set by our pre­vi­ous Gen 3 6.0L. With the boost gauge read­ing a full 29.2 psi (nearly 3 bar), the Big Bang Gen 4 6.0L threw down an in­cred­i­ble 1,543 hp and 1,256 lb-ft of torque.

Run­ning 118-oc­tane race gas and ice wa­ter through the in­ter­cooler core al­lowed us to get se­ri­ous with the boost on this 6.0L. This graph shows the power curves at the var­i­ous boost lev­els. Note that each suc­ces­sive jump in boost brought a sub­se­quent in­crease to the power through most of the power curve. This is why turbo builds are so ad­dic­tive. It is so easy to dra­mat­i­cally in­crease the power out­put, but take care not to get too greedy!

Here are the var­i­ous boost curves associated with the power curves pre­sented in Graph 2. Note that our over­sized S475 tur­bos spooled up the same at each boost level; the dif­fer­ence in boost pres­sure came only af­ter the de­sired pres­sure was reached. Each in­crease in boost brought a sim­i­lar in­crease in power. Ba­si­cally, the boost curves mir­rored the torque curves. We stopped at 29.2 psi af­ter top­ping out and dam­ag­ing the 3-bar MAP sen­sor.

This is an in­ter­est­ing com­par­i­son, as it shows the power out­put of the 6.0L at 1 bar (NA), 2 bar (14.7 psi of boost), and 3 bar (29.4 psi, or as close as we could get to these boost lev­els). Run in NA trim (1 bar or at­mo­spheric pres­sure), the 6.0L pro­duced 548 hp at 7,000 rpm and 462 lb-ft of torque at 5,500 rpm. Adding an ex­tra 1 bar of boost (ac­tu­ally 14.4 psi), the twin-turbo 6.0L pro­duced 1,078 hp and 869 lb-ft of torque. Step­ping up to nearly 2 bar of boost (3 bar to­tal or 29.2 psi), the power out­put of the 6.0L sky­rock­eted to 1,543 hp.

Newspapers in English

Newspapers from USA

© PressReader. All rights reserved.