The announcement that Dodge would be revisiting the legendary Hemi displacement of 392 inches for the 2011 Inaugural Edition Challenger reveals that the company is still well-coupled to its heritage. The engine would have to be special, as the original 392 was available only in the top of the line models for just two model years, 1957-58, and was the final revision of the engine architecture that had started in 1951 with the 331-inch Hemi. The 392 was a heavy-walled casting that was reserved solely for the Chrysler New Yorker, 300, and Imperial models; it disappeared into the sands of time for 1959, replaced by the new lighter, larger 413 wedge engine. With twin Carter WCFB carbs, that last first-generation Hemi was rated at 390 horses at the pinnacle of its development (in the 1957 Chrysler 300C and 1958 300D), a forerunner of the horsepower wars that would soon become part and parcel of marketing new cars in the coming decade.
Perhaps that final Hemi might have been just an aside in Chryslers storied engineering and performance history except that some hot rodders with names like Garlits, Karamesines, Sullivan, and Ivo figured out you could put one of those big Hemis in a slingshot-type dragster, fit it for a supercharger, tip the can of nitro methane to 95% or more, and HANG ON! The 180-, 190-, and 200-mph barriers in the quarter-mile had all fallen by 1965 as a result. The 392 fuel combination was so strong that it still was being used in the dragster and funny car ranks even after the Ramchargers team and others had gotten a firm grasp on the 426-inch second-generation revision in those applications some years later. In fact, engine builder Ed Donovan took the 392s basic design to design and build a quite successful all-aluminum race-only version he first produced in the early 1970s and continues to build today.
The new 392 (6.4L) HEMI is the latest street V8 for Chryslers performance models, and will supersede the previous 6.1L (370) version of the engine. The latest mill to wear the legendary HEMI moniker is the same basic block architecture as its 6.1L predecessor, with the displacement rise coming from both a minor bore increase (up .9 mm) and adding more stroke (3.7 mm). However, though similar to the 6.1, the 392 block is a unique casting, featuring different machining plus changes for strength, as well as modifications to the cooling and internal breathing passages.
The basic block, painted in the traditional Hemi orange hue, is topped with aluminum heads that make use of smooth core technology; this is a casting process that utilizes a special fine sand to form the runner cores. The runners themselves have been further massaged from their previous state, while valve size has also increased from the 6.1L versions 52.8mm intake / 40.5 mm exhaust to 54.3 mm/42.0 mm, respectively.
However, the crowning touch is the intake, which is why the torque curve was so smooth on the new engine. The SRTs new active intake design harkens somewhat back to the ram-tuning principles Chrysler engineers first comprehended during the late 1950s, but has greatly benefited from the computer modeling of airflow now available. Once reaching approximately 4,900 rpm, the active intake system starts physically revising the intake runner path and geometry (thus actually altering the induction tuning). This process, which was started on the SRV (Short Runner Valve) applications for 3.5L, 4.0L and the 5.7L truck engine, is for increased intake flow. That results in more power output, but the main advantage of the design is to improve low engine torque by having a longer runner available in the lower RPM level. The system uses the same internal parts as the SRV version, with cosmetic changes to its appearance and a different mount for the throttle body.
The engine is rated a 470 lbs-ft at 2900 rpm! The same number, 470, is also the official horsepower rating, greater than any prior street-based Hemi engine. With the package appearing like an an old school Hemi when first seen under the hood, plus the throaty sound from the well-tuned exhaust design, a displacement rich in heritage, and a powerband unlike anything to wear to ever wear that four-letter word before, my opinion is that the 392 Hemi will indeed be a Mopar milestone.
Photo Captions:Pit Slides collection photo / quartermilestones.com archive
Robert DAgostinos survivor 1957 300C convertible. The fact the engine proved so popular on the secondary circuit is one of the reasons these classic behemoths are so scarce today; many cars were bought, had the engine removed, and were unceremoniously sold for scrap.
The original 390-horse 392 Hemi in its dual-quad configuration in DAgostinos car. A handful were sold with fuel injection in 1958, though they proved to be very difficult to service and tune. The carburated versions used these twin .
By the mid-1960s, the 392s were out from the fenders of finned classics and wedged down into rail dragsters, topped with a supercharger, and breathing fat amounts of nitromethane. This is Don the Snake Prudhomme at NHRA Nationals in 1966. Ray Mann photo / quartermilestones.com archive
Even when the 426 version became popular, the 392 continued to thrive in drag racing. This is Vern Motes twin-engined Top Gas car being in the pits at Martin, Mich.,