If you're a fan of Chevy's LS family of engines, you already know the shortcuts to massive amounts of cheap horsepower—but what about for Mopar and third-generation Hemi fans? They don't have junkyards full of LQ4, LQ9, and LY6 equivalents—glamourless workhorses that serve duty in ¾-ton trucks then get plucked on the cheap, stuffed with an embarrassing array of low-cost power goodies, and live retirement in quadruple-digit hp form. If you're a Mopar fan, by comparison, your gearhead life looks far different, but that is changing thanks to a growing number of 392ci (6.4-liter) Hemis entering the secondary market. Even better, the third-gen 392 Hemi is starting to show up in junkyards, and if you want a leg up on the Chevy boys, you better pay attention to what we've got to say so you can deliver a proper beat-down when the time comes.
The 392 Hemi was first released in SRT trim (2011) in passenger car models like the Charger and Challenger. This initial iteration was rated at 470 hp and later rose to 485 hp in 2015. Ram Trucks from 2014-present (HD2500-up) use the BGE 392 Hemi (also known as the 6.4-liter) which is rated at 410 hp. In the Jeep lineup (2012-present), the Apache version of the 392 puts out a rated 470 hp. The third-generation 392 Hemi was equipped from its inception with variable valve timing (VVT) and multiple displacement system (MDS, automatic vehicles only).
Here's where it makes sense to mention a few of the important asterisks regarding the 392's dress of trade and rated horsepower. Vehicle models with manual transmissions did not use the MDS fuel-saving technology, and since no manual transmissions were offered in 392-equipped Rams, all 392 BGE Hemis (2014-present) have MDS. By contrast, you do sometimes find non-MDS Apache 392 Hemis (Dodge Challenger Scat Pack six-speed, 2015-present). Jeep products that have 392 Hemis are of the Apache variety and are all MDS equipped. All 392 Hemis (Apache and BGE, 2011-up) are based on the second version of the 5.7-liter third-gen Hemi called the Eagle (2009-present). Eagle-based Hemi cores are easily distinguished from earlier 2003-to-2008 non-VVT 5.7 Hemis (340hp) and 6.1-liter SRT8 Hemis (out of the scope of this article) by their prominent valve cover bulge.
In 2014, Chrysler decided to offer the 392ci Hemi in ¾-ton and larger Ram trucks and in the process traded some of the SRT Apache's outright horsepower for more durability margin and greater octane tolerance. In big gas engine (BGE) form, Ram's version of the 392 (called-out on trucks in liters as '6.4L') was rated at only 410 hp, but this fact hides the BGE's incremental improvements over the Apache passenger-car 392. Prior to 2014, Ram trucks had only been available with the 5.7-liter Hemi as its largest gas offering (the 6.7-liter Cummins diesel was an option, however). The truck version of the 392ci Hemi is, unbeknownst to most Mopar muscle car fans, blessed with some obscure improvements that will benefit the hot rodder. Though both provide internal dimensions larger than the 5.7-liter Hemi (the 392 has a 4.090-inch bore and 3.720-inch stroke, versus the 5.7's 3.917-inch bore and 3.578-inch stroke), the BGE version of the 392 has a lower compression ratio of 9.5:1 versus the passenger car's 10.9:1. The BGE's timing cover and front end accessory dress (FEAD) is also different from the Apache, and some of the BGE's design features versus the Apache are present in the 6.2-liter Hellcat Hemi—a boon to hot rodders looking for big power on the cheap.
Our exploration of the BGE 392 began while rebuilding a 5.7-liter Eagle Hemi at IMM Engines in Indio, California (check out that story here). IMM builds a fair amount of Chrysler high-performance engines and is always on the lookout for nice cores, and during this time an orphaned BGE 392 from a 2016 Ram 2500HD truck came knocking. Rejected by core buyers because this specific engine was known to be non-running, the scrapyard offered it to us for $400. According to national core brokers EngineQuest Cores & Recycling out of Las Vegas, typical 392 BGE cores sell for between $1,000 and $1,500, so we were potentially starting out anywhere between $600 and $1,100 ahead of the game. Did it have internal damage like wiped bearings, melted pistons, or a mangled valvetrain? We'd soon find out. If things looked good, we decided we'd do a full build-up and dyno-test series, but we couldn't put the cart before the horse. First thing's first: Take this baby apart and discover the good, the bad, and the ugly!
There was a fair amount of work involved with stripping down the BGE 392 to the point where we could start making sense of it. The EGR apparatus—which is unique to Ram trucks—was removed, followed by the exhaust manifolds and the water pump. Here we note our first differences between the BGE 392 and the Apache 392: The BGE accessory dress extends further out than the Apache passenger car dress, and the timing cover is different. The BGE 392 Hemi cover is deeper, wider, and taller than the Apache timing cover, and it's worth noting that Hemi timing covers are a function of the vehicles they are installed in, not the engine size, such that Hemis in trucks (both 5.7-liter Hemi and BGE 392 Hemi) have the same timing covers (if not the same part numbers) and FEAD. Likewise, timing covers in passenger cars (Apache 392 and 5.7-liter Hemi) are the same covers and FEAD.
In this composite image, the BGE 392 timing cover corresponds to "A" and is the same type found on all Ram V-8 Hemi truck applications (5.7-liter and 392 BGE Hemi). Timing cover "B" is the Hellcat Hemi unit, and timing cover "C" is the Eagle/Apache passenger-car unit (tip: all passenger car Hemis except Hellcat share the same timing cover and FEAD). Common practice is to convert BGE 392 Hemis to a passenger car timing cover and FEAD for a more compact vehicle installation, but Holley's Premium Mid-Mount Accessory System for Hemis goes quite a bit farther in tucking the accessories close to the engine, and also includes a proprietary timing cover that integrates all the mounting points and idler pulleys inboard. At a tick over $2,500, the Holley FEAD is expensive, but solves enough installation, plumbing, wiring, and fabrication headaches that the cost is probably worth it. It's a kit we'll be looking a lot harder at in the coming months.
The damper/crank pulley assembly on the third-gen Hemi is pressed onto the crank snout, and getting it off requires a claw-style puller and a little heat persuasion from a propane torch. Note that the damper/crank pulley on the third-gen Hemi does not have a keyway and is held in place completely by its interference fit. In this photo, note how far forward the oil filter adapter is on the BGE 392, a potential interference problem for some swaps. The Hellcat's oil filter adapter will work, but you will need to source it directly through Mopar replacement parts. This involves making a pair of AN -12 lines with ORB fittings (o-ring boss) if you want to remote-mount an external oil cooler.
As we continued to crack open the junkyard BGE 392, we discovered one possible reason why our unit was deemed unusable: There was surface rust in cylinder bores 4 and 8 (arrows) that may have frozen the engine. You can see the distinct water line particularly well on the combustion chamber and piston crown (top arrow) where coolant or rainwater collected. Our engine lacked an intake manifold when we got it and our suspicion is that it sat outside on its side uncovered for a while before being rescued. This should easily clean up with a .005-inch overbore. If boring out your BGE 392 Hemi, know that .020-inch over is the absolute limit you can go.
The BGE 392's cylinder heads are where we hit the jackpot. Compare the BGE 392 Hemi cylinder head (A) to a photo we took at the Chrysler Technical Center in 2014 which shows the 392 Apache cylinder head (B) next to the then-new Hellcat Hemi cylinder head (C). What wasn't disclosed to us then that we now can confirm is that in areas where it counts the most, the BGE 392 Hemi cylinder head casting is the same as the Hellcat head casting, as you can see from the cast-in support gussets (finger). There is a difference in the intake manifold bolt pattern between the BGE and Hellcat heads; the intake flange is different on Hellcat with bolt positions being closer to the valve cover on the Hellcat and in the middle of the intake port for the BGE. We've also confirmed that the metallurgy of the BGE and Hellcat heads is the same 356-T6 (the Apache head is a softer 319 alloy). The BGE 392's valves are different from the Hellcat. According to Modern Muscle Xtreme's Byron Walker, the BGE has solid-stem intake valves, not hollow ones, and though the exhaust valves on Ram HD (Chassis Cab) 3500, 4500, and 5500 series are sodium-filled, they are not the race-quality units found in the Hellcat. The BGE's sodium-filled exhaust valves—where equipped—can be distinguished by a dark DLC coating on their valve faces and stems. Our BGE 392 was from a 2500 series and has the standard non-coated Apache 392 valves (2.13-/1.65-inch diameter). Stock port flow in untouched form approaches 350 cfm at .600-inch valve lift.
We got another good omen when we pulled off the oil pan and found nothing bad in the pan like engine parts, sludge, or bearing material. What oil remained looked good and we observed no shiny specks.
The VVT camshaft from the BGE 392 Hemi is not notable other than that it proved to be undamaged and all the lifters (including those from MDS cylinders 1, 4, 6, and 7) looked to be in good shape. Failure of the roller lifters in Hemi engines is a known issue so we were happy to see none of that here. We won't be reusing any of the BGE's valvetrain components other than the rocker arms, timing chain assembly, and valves, but the sign of no damage is encouraging.
Here's a sneak peek of our new Modern Muscle Xtreme (MMX) Max Effort hydraulic roller camshaft kit that specs out at .598/.595-inch gross valve lift, with 224/236 degrees duration at .050-inch lift on a 114-degree LSA. This will be paired to MMX .083-inch-wall hardened pushrods (8.075-inch, exhaust; 6.775-inch, intake), new non-MDS Mopar lifters, a Comp Cams 5760 VVT lock-out kit, and a drop-in BGE spring kit from Manton. This cam is optimized for boost, which we'll be adding to the 392 BGE Hemi a few story segments down the line, so stay tuned.
Below deck, the BGE 392 Hemi is built like a bomb shelter, its full-skirted block, high-nickel alloy, cross-bolted mains, and fortified bulkheads able to support north of 1,000 hp with only a bearing upgrade. Shown here is another BGE 392 exclusive: a pair of copper-lined bearings in the No. 4 main gallery, which is compared here with the standard bearing in the No. 3 main cap. The firing order puts more stress on the No. 4 main so the factory performs a standard upgrade in that position. We found no significant wear in any of the main or rod journals, and barring the detection of any hairline cracks in the block or cylinder heads, this 392 BGE Hemi checks out A-OK.
This beautiful piece of jewelry is the BGE's forged-steel crank, which was rumored at the 392's introduction to be manufactured by Scat. If the rest of our BGE 392 core was junk, the $400 cost of admission would still be less than what this crank is worth. The BGE 392 crankshaft forging is the same one used to make the unit in the Hellcat Redeye Hemi—the only difference is in the stroke length and the Hellcat's inclusion of induction-hardened journals. Apache and BGE 392s get a 3.720-inch stroke while the Hellcat Redeye gets a shorter 3.578-inch stroke. If you were going to build a snot-nosed 5.7-liter, this is the piece you'd use to arrive at 354ci. This factory forging is cleared for reliable use up to 1,200 hp.
The BGE 392's pistons are lightweight hypereutectic castings, and although their high silicon content bodes well for low thermal expansion, they don't have the beefcake to withstand the big boost we plan on throwing at the Junkyard 392. Common wisdom is that these units can handle around 650 hp safely before they become susceptible to damage from cracking or pinching a ring land. In certain cases, stock BGE 392 Hemi pistons and rods can work up to 900 hp for limited blasts, but only where the rod bolts are upgraded to ARP units and boost is limited to 6 psi. This would be a situation where power is more a product of the added rpm and not added boost. It's also worth noting that the BGE 392 piston differs from Apache piston in that its top ring land is lower than the one in the Apache 392 (Ram engineers needed the BGE 392 to be rated for full torque on 87 octane for 12 minutes at a time). Like the Apache 392, the BGE 392's forged powdered-metal rods have full-floating wrist pins and matched cracked rod caps, and differ slightly from the Apache rods; BGE rods have a bevel cut on the small end like the Hellcat rods, versus the Apache's straight-cut small end. Neither the BGE nor the Apache rods have the tensile strength of a true forging that can withstand significant boost. The BGE piston crowns exhibit a recessed dish with a dome and a pair of valve reliefs for a final compression ratio of 9.5:1 versus the Apache's 10.9:1.
The BGE 392 block is as good as it gets. In strength, it's the equal to the Hellcat/Redeye block, down to the water jackets, main bulkheads, high-nickel alloy, and lube circuit. It even has piston oil squirters, though the squirters in the Hellcat/Redeye block are clocked and targeted differently due to the different design around the piston pin boss area. Though it's sometimes debated, prevalent thinking is that these squirters should be retained to provide piston cooling under load but should be temporarily removed to avoid damage when performing machine operations to the block. We started out comparing GM's line of 6.0-liter iron-block LS engines, and none of them have this kind of beefcake. A BGE 392 Hemi core might carry a cost premium over a 6.0-liter iron-block LS, but at the 1,000 hp level the BGE will have proven to be the bargain once the BGE's block, forged crank, and Hellcat cylinder heads are considered.
The water jacket design of the BGE Hemi is shared with the Hellcat Hemi block. Arrow A points to a display cutaway of the Hellcat Hemi block, showing the water jacket's 100-percent coverage of the top ring's sweep. At the time of the photo, Chrysler Hellcat Hemi engineer Gregg Black told us it was deeper than the Apache 392's water jacket. For reference, the top of the Hellcat piston is shown 3.57 inches below the deck, making the water jacket about 4 inches deep. A quick probe of the depth of the BGE's water jacket (B) shows it to be about the same. With the BGE block's upgrade to a high-nickel alloy, the tall water jacket relative to the Apache block carries no strength penalty.
Our 392ci BGE Hemi block is completely stripped and ready for inspection and hot-tanking. An identical new 392 high-nickel BGE block from Mopar will set you back $1,750. Other than paint color (Hellcat blocks are orange, BGE blocks are black) and the additional process of torque-plate honing on factory Hellcat blocks, the BGE is identical to the Hellcat block. Once cleaned it will be easy to check for cracks and signs of fatigue more closely. Our work is being performed by IMM Engines of Indio, California.
The 392 BGE Hemi block is easily identified by the large cast letters "BGE" just above the oil pan rail on the driver's side of the block. There is also a similar mark cast into the rear of the block within the bellhousing perimeter (yellow arrows). The BGE 392 and Hellcat block castings are different through the 2017 model year, but starting in 2018 with the Demon's release, all BGE and supercharged blocks (Demon, Hellcat, Redeye, Super Stock) are the same casting. According to Holley engineer Eric Cunningham, the key difference between supercharged blocks and all other Hemi blocks including the BGE block (all years) is that the oil pan bolt pattern for supercharged blocks is different.
It would be nice if the factory put a matching VIN number somewhere on the block, but it doesn't. It does, however, place an engine serial number on a sticker found on the driver-side valve cover (lower-right inset) and it matches a number brinelled into a pad cast on the passenger-side oil pan rail (yellow arrow). Our BGE 392 reads "TNXE6020610349" and all those numbers mean something, though none of them are terribly important to decoding what's inside (they do, however, allow you to match the valve cover to the correct block). In this case "TNXE6" refers to the V-8 engine plant in Saltillo, Mexico, the only source of Gen III Hemi engines. In position A, three digits show the sequence in the Julian calendar from 001 (the first day of the year) to 365 (the last day of the year). This engine was built on January 20. Position B is the year (2016 in our case), Position C is the factory shift (first shift in our case), and the final four numbers of position D make up the sequence number for that day (ours was the 349th engine built in Saltillo, Mexico, on January 20, 2016).
To get a head start on our build we ordered MMX's 392 Hemi Forged 2618 Drop-In Piston and Rod Power Package, which contains forged 2618 alloy pistons made to spec by Mahle for MMX. These feature a slightly recessed chamber with large valve reliefs for higher-lift cams and a compression ratio ranging between 9.7 and 10.1:1, depending on gasket thickness and deck height. When combined with MMX's 6.200-inch Molnar forged rods the rotating assembly needs no balancing, a huge time and cost savings.
The MMX/Mahle drop-in piston on the right is compared with the stock 392 BGE piston and shows how Mahle revises the 392's 1.21-inch compression height to provide for more strength and protection at the top ring land for lots of boost or nitrous. A thermal barrier coating helps keep hot spots, a major cause of pre-ignition and detonation, from forming.
MMX's Drop-In Piston and Rod Power Package contains Molnar forged H-beam rods (left). The stock BGE 392 powdered-metal rod and DLC wristpin is on the right. The stock rods, along with the stock cast pistons, are the weak link in the BGE 392 Hemi so we're replacing them with beefy Molnar forged rods with a stock 6.200-inch length. Note the MMX-spec Molnar rod uses a German tool steel wrist pin with a larger .948-inch diameter and a fat .217-inch wall thickness. Its narrower width offsets its thicker wall, making it stronger without creating an over-balance on the small end. When combined with the MMX/Mahle forged piston, the Molnar rod/pin combo is a no-balance drop-in.