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Build A Vintage 392 Hemi On The Cheap & Get 436 HP!

HOT ROD logo HOT ROD 8/31/2017 Hot Rod Network Staff
001-392-hemi-on-dyno.JPG Build A Vintage 392 Hemi On The Cheap & Get 436 HP!

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."

Research

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!

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


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