What's The Difference Between Gm's L86 & L87 Engines?

The biggest quality betwixt L86s and L87s is that L86s have occasional complaints and 28,000 L87 failures happened earlier GM recalled 600,000 trucks successful nan U.S. alone. The 2014-2018 L86 and 2019-current L87 engines are portion of Chevrolet's Gen-V LT "small-block" V8 family. Sorry for nan quotes, but group emotion arguing astir Chevy's small-block V8 architecture and whether LS and LT engines are successors aliases portion of nan aforesaid lineage. Anywho, L86s and L87s are 6.2-liter overhead valve — aliases pushrod, if you for illustration — V8s pinch aluminum blocks and heads, nonstop injection, adaptable valve timing, and oil-jet piston cooling. They each nutrient 420 hp and 460 pound-feet of torque.

The 6.2-liter V8s successful Corvettes and Camaros are called "LT1," which is simply a sanction pilfered from nan '70s Gen-I and '90s Gen-II 350s. GM loves reusing classical motor designations to make it difficult to find nan nonstop V8 you want successful a Google search. Trucks get nan L83 (which was besides nan moniker of nan Cross-Fire Injection Gen-I 350 successful '82 and '84 Corvettes) successful 5.3-liter displacement, arsenic good arsenic nan 6.2-liter L86 and L87. The motortruck engines besides characteristic "EcoTec3" branding.

Where nan L86 and L87 disagree is successful efficiency-managing technology. L86s person Active Fuel Management (AFM) that shuts disconnected 4 cylinders nether ray loads. L87s person Dynamic Fuel Management (DFM) and tin run connected immoderate cylinders they want, which tin beryllium arsenic fewer arsenic two. Unlike nan L86, L87s besides gained automatic start/stop capability. Oh, and thousands of L87s person grenaded themselves because of grounded connecting rods and crankshaft main bearings, that's different difference. And yet J.D. Power featured Chevrolet Silverados and Tahoes successful its 2023 Dependability Awards, moreover though that twelvemonth is successful nan bosom of L87 problem territory. 

There person been complaints of both L86s and L87s (and moreover LT1s and L83s) experiencing lifter failures. Reports bespeak nan AFM and DFM systems origin lifter noise and accelerate their demise, so Engine Labs tore unfastened 3 L83s and an L86 pinch grounded lifters. They discovered that it was nan normal lifters that grounded alternatively than those responsible for cylinder shutoff. Some of nan lifter problems could stem from nan truth that each direct-injected Gen-V LTs tin build up c connected nan intake valves, which is simply a communal problem for direct-injection engines successful general. After capable c cakes on, usually astatine nan apical of nan valvestems, nan valves tin get stuck and put other accent connected nan remainder of nan valvetrain — nan lifters, pushrods, and camshaft.

That covers immoderate similarities, but what are nan differences betwixt engines for illustration nan L86, L87, and LT1? Well, not much, really. Basically, nan L86 and L87 person longer runners connected nan intake to stress low-end torque, arsenic opposed to nan higher-rpm powerfulness nan LT1 is tuned to deliver. Also, nan motortruck LT has a deeper lipid pan. Other than that, nan LT1, L86, and L87 engines are identical*.

Oh, there's that darn asterisk. Obviously they're not identical; aft all, LT1s and L86s aren't presently nether investigation by nan National Highway Traffic Safety Administration for motor failures, nor are they nan taxable of a monolithic recall. This isn't truthful overmuch owed to nan L87 having creation flaws arsenic overmuch arsenic suffering from manufacturing defects. Missing wrist pin clips connected connecting rods, improperly vanished crankshafts pinch incorrect dimensions, and rod bearings that build up sediment support sidelining L87s. In nan end, cranks from supplier Questum Macimex and connecting rods from American Axle & Manufacturing may beryllium to blame.

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Let's not attraction connected L87 failures astatine nan moment. Rather, let's item really start/stop and DFM improved substance ratio successful nan L87 complete nan L86. The U.S. Department of Energy's ratings astatine fueleconomy.gov show that an L86-equipped 2018 Chevrolet Silverado four-door pinch each wheel-drive (AWD) gets 20 mpg highway/15 mpg city/17 mpg combined. Meanwhile, an identically spec'd 2019 Chevrolet Silverado pinch nan L87 has — and get fresh to prime your jaw up from nan level — a standing of 20 mpg highway/16 mpg city/17 mpg combined.

Well, miles-per-gallon isn't everything. The L87 whitethorn person little tailpipe emissions! Let's look astatine nan model sticker for a 2024 GMC Sierra 1500 Denali Ultimate pinch nan Ford co-developed 10-speed automatic transmission. It says it puts retired 539 grams of CO2 per mile. Now let's look astatine nan model sticker for a 2018 GMC Sierra Denali pinch nan aged 8-speed. It's besides a unit cab, besides 4WD, besides has a 3.23 rear axle ratio, and it has nan 6.2 EcoTec3 — which successful this lawsuit would beryllium an L86. Oh, it puts retired 524 grams of CO2 per mile. That puts it astatine 15 grams little than nan newer, much businesslike L87. Still, nan smog standing is simply a 3 retired of 10 connected nan 2018 and a 6 retired of 10 for nan 2024, truthful nan L87 astatine slightest manages to triumph there.

So, there. The biggest differences betwixt L86s and L87s are infinitesimal ratio improvements, CO2 and smog output, and a world callback of (currently) astir 721,000 vehicles.