It's hard to imagine nearly 70 years have passed since Chrysler first introduced the wonders of the highly efficient hemispherical combustion chamber to American motorists—and hot rodders. Back in 1951 when those first 331 Fire Power equipped Saratogas, New Yorkers, and Imperials introduced owners to the thrill of stop-light dominance, the concept of smoking the rear tires away from an intersection wasn't yet "a thing."

Sure, kids in their hot rods awoke slumbering suburbanites in the wee hours as their chopped-down, flathead-powered Deuce roadsters spun rubber after midnight, but it was the 331 Hemi that brought the gobs of torque necessary to boil the rear tires at will from a dead stop in a bone-stock, full-sized Chrysler passenger car. While part of the recipe for rubber incineration was Chrysler's 1951 replacement of the slippery Fluid Drive coupling with a four-element torque converter, the 180-horsepower, 312 lb-ft 331ci Fire Power Hemi was at the core of the revolution.

So here we are now, some 66 years after Chrysler's hemispherical makeover and once again, Hemi-powered drones scream down the boulevard (to borrow from Bruce Springsteen's iconic hit song Born to Run). Amazing but true, since 2003, Hemi power has elevated Chrysler from the doldrums as the maker of front-drive-only transportation modules and the cab-forward LH era to creators of the world's first muscle car capable of cranking a 9.60 and pulling a wheelie! Yep, we're talking about the 2018 Dodge Challenger SRT Demon.

These are good times indeed but let's not lose sight of the fact it wouldn't be happening if not for the exploits of the first-generation Hemis of 1951 - 1958. While the modern 5.7L, 6.1L, 6.2 Hellcat/Demon, and 6.4L Gen III and classic Gen II 426 Street and Race Hemis get all the glory today, we can't forget the one that started it all: the mighty Chrysler Fire Power. Bolstered by the similar (but not identical) 1952 DeSoto Fire Dome and 1953 Dodge Red Ram, hemispheres have struck fear into the competition ever since.

In this story we'll explore the construction of a 1957-vintage 392 Hemi and test it with intake and exhaust goodies to see how they compliment the inherent ability of Chrysler's legendary "whale motor" to deliver the happy combination of prodigious low-end torque and upper-rpm horsepower.

We tagged along as Donnie Wood and his crew at R.A.D. Auto Machine refurbished a 392 Fire Power with mild street and strip cruising in mind. Traditional dual-quad induction was compared to a modern high-rise single quad from Hot Heads, and the stock cast-iron log-type exhaust manifolds were compared to Hot Heads' tube steel block huggers.

The results are impressive and prove that Hemis—vintage and new alike—offer unsurpassed breathing potential and eyeball appeal like no other V8 engine ever made!

See all 30 photos After a 0.040 overbore, align honing, and deck squaring, the block is ready for assembly. Unlike the Gen II and Gen III Hemi blocks, the Gen I lacks the deep skirt oil pan rail that makes cross-bolted main caps possible. It's still plenty stout for 600 horsepower and then some.

See all 30 photos After reducing the main and rod journals by 0.010 to reverse wear, R.A.D. sets the factory stock forged steel crank in place. At 68 pounds, the 392 crank is one pound lighter than a Gen II 426 Street Hemi forging (69 pounds) and 12.4 pounds heavier than a forged steel 340 small-block crank (55.6 pounds). All Gen I Hemi cranks feature non-threaded eight-bolt output flanges. Remember this when attaching flywheels and flex plates.

See all 30 photos Though girdles and upgraded forged steel main caps are available for the early Hemi, this mild-mannered street/strip mill gets by safely with the stock cast-iron main caps. The 392 main journal diameters measure 2.6875 inches. (The 331ci and 354ci sizes are 2.500 inches.) Cranks and blocks for 392s are a breed apart. The cap fasteners go to 90 ft-lb.

See all 30 photos KB Silv-O-Lite hypereutectic pistons deliver a pump-gas-friendly 9.5:1 compression ratio. The mild compression ratio negates the need for heavy high-dome pistons to fill the Hemi's 103cc chambers.

See all 30 photos Though the stock 6.950-inch rods are retained, the beams were polished to remove forging marks and potential stress risers. The floating piston pins are retained by spiral locks.

See all 30 photos High-quality ARP rod bolts are tightened to 52 ft-lb. In this naturally aspirated 6,500rpm application, the refurbished stock bottom end is perfectly adequate, though up-sized forged and billet items are readily available.

See all 30 photos The Gen I Hemi oil pump may resemble the LA unit (273, 318, 340, and 360) but has different mounting bolt locations and is not interchangeable. Though Milodon, Hot Heads, and others offer race-capable pumps, a basic new NOS item was obtained for this boulevard bruiser. The stock pickup tube and screen match the stock passenger car sourced center-sump oil pan.

See all 30 photos Early Hemi cams are currently available from mild to wild, but you need rare factory or costly aftermarket adjustable rocker arms to run solid lifters. Since our Hemi has the common one-piece (non-adjustable) rocker arms, we went for a hydraulic, flat-tappet cam. It's an Isky Mega 280 with 0.485-inch lift.

See all 30 photos R.A.D. found this vintage two-piece FGT front cover and housing to shield the Cloyes True Roller timing set (part No. 9-1103). The removable cover is set up for a Hilborn-type cam-driven fuel pump and is probably from a marine application. Here, it adds eyeball appeal and function.

See all 30 photos Numerous sources exist for hydraulic (and solid) lifters. Ours are from Isky. A liberal coat of assembly lube and Joe Gibbs Racing anti-scuff moly lube are applied during installation.

See all 30 photos Best composite head gaskets (part No. 585) are part of the recipe that yields a 9.5:1 compression ratio. Once squeezed, they're 0.040 inch thick. The open-tappet chamber will be sealed by the stock stamped tin valley cover after it gets a thorough clean out. Oil fill and crankcase ventilation are handled by an opening in the cover.

See all 30 photos Though 392 heads are excellent, the 331 head is known to have a slightly better port floor contour. Thus, a set of 1955-vintage 331 Hemi heads (casting number 1556157-1) have been selected. The 2.00-/1.750-inch valve's head diameters remain stock. The 103cc combustion chambers remain stock though the ports have been polished, and bowl relief work was performed.

See all 30 photos For kicks, we compared the 331 head (top) to a 1964-vintage 426 Race Hemi head. The major differences are (331 vs 426): 64.4 vs. 58.2 lbs bare weight, 103cc vs. 172cc chamber volume, 2.00-/1.75-inch vs. 2.25-/1.94-inch valves, and 4.5625-inch vs. 4.800-inch bore spacing. The included valve angle is the same at 58 degrees.

See all 30 photos Like Gen II and Gen III Hemis, the Gen I heads are interchangeable side-to-side, but must have caps placed over unused water passage outlets at the fire wall end. Note the shiny surfaces of the ported and polished intake ports. The exhaust ports are just as nice. We didn't flow test the heads but suspect the effort improved flow by about 10 percent.

See all 30 photos To keep pace with the Isky cam and assure 6,500rpm stability, Hot Heads dual valve springs (part No. 40062) are used with stock retainers and locks. Spring force is 135 pounds closed and 325 pounds at 0.500-inch lift with a 1.700-inch installed height.

See all 30 photos It may not be as simple as a small-block Chevy's stud mounted, ball-pivot, stamped steel rocker arm setup, but the Hemi's trademark double rocker shaft architecture is the only way to connect the wildly divergent valve tip angles to the camshaft. The rocker shaft stand fasteners do double duty as head bolts and tighten to 85 lb-ft in two steps.

See all 30 photos Though stock one-piece pushrods are acceptable at this level of performance, to enable fine tuning of lifter pre-load with the hydraulic camshaft Hot Heads 3/8-inch diameter chrome moly adjustable push rods (part No. 21086) are used. Proper setting is a half turn beyond zero plunger lash. Adjustable rocker arms were installed in 1955-'58 Chrysler 300 "letter cars" but cost over $2,000 when found today. Aftermarket rockers are no less expensive.

See all 30 photos R.A.D. gets set to install the vintage M/T finned aluminum rocker covers. When the Whale motor ruled the world, these beauties were the ultimate Hemi fashion statement on everything from small town hot rods to Don Garlits' Swamp Rat rail dragster.

See all 30 photos Though similar in appearance to Gen II 426 Hemis, Gen I Chrysler Hemi spark plug tubes (6.100 inches long) are 0.250 shorter and are formed for different top seals. Most aftermarket wires sets (aside from length concerns) are interchangeable. Autolite #65 spark plugs are used. The 2003-up Gen III Hemi eliminated the separate spark plug tubes for integrally-cast tunnels.

See all 30 photos When Chrysler grew the 1951-'56 331ci and 354ci into the 1957-'58 392ci, the deck height was increased from 10.32 to 10.865 inches. Further complicating things, our shorter 331 heads render the stock thermostat housing (foreground) too short. Hot Heads solved the problem with this adjustable braided hose kit (part No. 21404). Note the stock oil fill neck, mandatory with our non-vented M/T rocker covers.

See all 30 photos The Weiand dual-plane 8-bbl intake manifold (part No. 7263) has been a go-to street and strip unit for decades and is still available. How will it stack up against Hot Heads' high-rise, dual-plane offering (part No. 50000)?

See all 30 photos Because our Frankenstein block and head combo yields a non-stock span between intake flanges, Weiand adapter flanges (part No. 8203) are needed for both manifolds.

See all 30 photos The early Hemi's close relationship to the Mopar 273 - 360 small-block family allows sharing of distributors with only minor tweaking. A box-stock Pertronix Flame-Thrower billet unit (part No. D141700) needs only a special Hot Heads intermediate drive shaft/gear assembly and alignment collar (in hand) to complete the ignition. Timing is set at 32 degrees BTDC, all in by 3,000 rpm. All factory distributors employed dual points, even the base two-barrel job!

See all 30 photos Our tests will pit the stock center-dump exhaust manifolds (in hand) against Hot Heads' steel tube block-huggers with 1 7/8-inch primary tubes. Hot Heads also offers a clone of the large-diameter Chrysler 300 iron manifold (part No. 60018) as well as a selection of full-length tuned headers for the Gen I Hemi.

See all 30 photos

See all 30 photos With a box-stock Quick Fuel 750cfm double-pumper atop the Hot Heads high-rise and cast-iron exhaust manifolds, the Fire Power made 408 hp at 5,500 rpm and 463.6 lb-ft at 3,300 rpm. Considering the mild cam, single-digit compression ratio, and restrictive exhaust tract, it's a strong showing. Now let's swap to headers

See all 30 photos Not surprisingly, the reduction in exhaust back pressure cranked things up to 431 horsepower at 5,500 rpm and 489.2 lb-ft at 3,700 rpm. Those are gains of 23 hp and 25.6-lb-ft. But what happens when we swap the modern single-quad with an old-school dual-quad setup?

See all 30 photos With two box-stock 500cfm Edelbrock Performers (part No. 1405) on the vintage Weiand casting, eye appeal goes through the roof. Contact between the carb's linkage plates and manifold fasteners forced some trimming. Inch-tall carb spacers would also work but we wanted to keep it simple. The Hot Heads headers remained in place.

See all 30 photos Bigger carbs should equal bigger power numbers, right? Not always. With 436.5 horsepower at 5,700 rpm, a mere 6.5 hp was added over the single quad. What's more shocking is the impact on torque, which fell ten percent (48.8 lb-ft) from 489.2 to 440.4 lb-ft at 4,400 rpm. Bob Walker's design team really did their homework when they developed the Hot Heads high-rise single-quad dual-plane unit!

Fast Facts

1957 Chrysler Fire Power Hemi

Bore: 4.040-inch

Stroke: 3.900-inch

Displacement 398 cubic inches

Compression ratio: 9.5:1

Camshaft: Isky 280 Mega hydraulic, flat-tappet

Valve lift: 0.485-/0.485-inch

Duration: 232/232 degrees at 0.050-inch lift

Lobe separation angle: 108 degrees

Rocker arms: stock steel, shaft-mounted, non-adjustable type

Lifters: Hot Heads 0.904-inch hydraulic flat-tappet

Pushrods: Hot Heads 5/16-inch diameter adjustable tip

Piston rings: Speed Pro 24122, gapped at 0.018, 0.020 (top and second)

Piston: KB Silv-O-Lite hypereutectic cast aluminum,

0.040-inch oversize (part No. 24536-040)

Block: stock iron, bored 0.040-inch over to 4.040,

block ID stamping CE5713234

Crankshaft: stock forging, with main and rod journals cut 0.010 inch

Rods: stock forged, 6.950-inch with polished beams and ARP fasteners

Main journal diameter: 2.6775 inch (0.010 under)

Rod journal diameter: 2.3640 inch (0.010 under)

Bearings: Federal Mogul (0.010 under)

Cylinder head: 1955-vintage iron castings from 331ci Hemi, ported and polished,

casting number 1556157-1

Chamber volume: 103cc

Intake valve diameter: 2.00-inch (stock)

Exhaust valve diameter: 1.750-inch (stock)

Valve springs: Hot Heads double, 1.550-inch installed height, 135 lbs closed seat,

325 lbs at 0.500 lift

Spring retainers: stock pressed steel

Head gasket: Best composite, PN 585, 0.040 crushed thickness

Intake manifold: Weiand (part No. 50010) 2x4 versus Hot Heads (par No. 50020) Hi-Rise

single four-barrel

Carburetor: dual 500 cfm Edelbrock Performers versus Quick Fuel 750cfm

Double-pumper

Header: stock center-outlet cast-iron manifolds versus Hot Heads

block-hugger headers (part No. 60010)

Ignition: Pertronix Flame Thrower billet aluminum (part No. D141700)

Damper: Power Bond, indexed (part No. PB1115ST)

Water pump: Moroso electric dyno pump

Oil pan: stock center-sump passenger car, 5 quarts

Oil pump: NOS with stock pickup and screen

Fuel: Sunoco 92-octane unleaded

Timing advance: 32 degrees