Hot Rod's Early HEMI Guide

1st Gen HEMI how-tos, tips and tricks.
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Hot Rod's Early HEMI Guide

Post by scottm »


The Early Hemi Guide of Death ... _of_death/
Among hot rod engines, the flathead Ford V8 and small-block Chevy V8 are usually considered the most significant milestone powerplants. But there's another mill that ranks right up there with the Big Two: Chrysler's first-generation Hemi of the '50s, Detroit's first serious attempt to build a mass-produced, no-compromise engine using advanced (for the time) hemispherical combustion chamber technology previously reserved for aircraft or exotic sports cars.

Chrysler's early Hemi grew out of experience gained during World War II with developing Hemi-headed aircraft and tank engines for the war effort. After the war, Chrysler needed to remain competitive with the new Caddy and Olds overhead-valve V8s, so it began developing brand-new motors. Early testing of alternative head and valve layouts revealed that the hemispherical combustion chamber was superior to other designs.

The result was the 1951 debut of the 331 Chrysler Hemi. DeSoto and Dodge Hemis followed in 1952 and 1953, respectively. Each division's Hemi had a unique block, heads, and cylinder-bore spacing. Virtually no internal parts interchange between them. In the Chrysler line, the 331 grew to 354 ci in 1956, and finally--using a raised-deck block--to 392 for '57 to '58. In the process, hard-core racers quickly discovered the engine's potential. The Hemi's efficient combustion chambers responded well to the new high-octane gas and was unsurpassed while running on alcohol and later nitromethane, a legacy maintained by the Hemi's modern-day descendents.

Alas, the engine was more massive for its displacement than its competitors' products, making it harder to package in increasingly streamlined engine compartments. The heads' fully machined combustion chambers and complicated valve layout made it costly to produce. In 1959, Chrysler turned to the cheaper wedge motors, bringing the first-gen Hemi's short, eight-year run to a close.

Today, first-gen Hemis and their full-race Donovan 417 offspring live on in nostalgia fuel racing. Street rodders tired of cookie-cutter, me-too small-blocks are snapping up old Hemis for use in retro rods. Their unique, in-your-face appearance makes a badass engine swap, even in a classic muscle car. For many years, early Hemi parts were scarce, but renewed interest in them has made it profitable for aftermarket parts vendors to push out improved parts that now make those old Hemis bigger and faster than they ever were. Pickings are still a little slim for the DeSoto and Dodge versions, but the situation is improving even for those oddball offshoots. Nevertheless, this article will concentrate on the more available Chrysler Hemi. As of early 2012, the only major parts lacking for fully resurrecting these engines are new blocks and affordable aftermarket cranks, but we expect this to be remedied by early next year.

For the scoop on first-gen Hemis, we consulted Gene Adams, one of the pioneers of early Hemi development who continues to build and race them to this day; Bob McKray, ace Hemi engine builder and head porter; Gary Patrick of (formerly Rocker Arm Specialist); and Bob Walker, owner of Hot Heads, your complete one-stop source for early Chrysler, Dodge, and DeSoto Hemi hot rod parts.

Chrysler Vs. DeSoto Vs. Dodge

Early Hemi block lengths from the rear bellhousing face to the front of an adopted Chevy V8 short water pump pulley mounting flange: Dodge, 27 inches; DeSoto, 27-1/4 inches; Chrysler (without integral bellhousing), 28-3/4 inches.


All production blocks are cast iron and have two-bolt main caps. If it passes a sonic check, Adams says you can overbore a normally aspirated 331 up to 0.125 inch (1/8 over stock). A 354 or 392 can take 0.060 over. For supercharged gas street engines, you need to maintain at least 0.125-inch wall thickness after overbore on the thin or thrust side, which usually mandates limiting the max overbore to 0.030 inch.

Unbeefed production blocks have adequate strength for normal usage--about 400 to 500 hp on a 354, 500 to 600 on a 392. Replacing your 50-year-old bolts with ARP main and head studs provides good insurance. As Adams puts it, "Don't use bolts--use studs everywhere you can." Nevertheless, running more than 11.0 to 12.0:1 compression, cramming in 8 psi or more of boost, or packing lots of nitrous or nitro stands a good chance of failing the cylinder walls and main webs. In the '60s, the main solution (pun intended) was to use a support girdle for the two-bolt caps in addition to filling the block with concrete (or half filling them for street use). New four-bolt conversion caps have made girdles obsolete (although TR Waters still sells them).

Race-only aluminum blocks have been developed (as in the Donovan 417), but they lack water jackets and/or won't accept most internal or external production parts. Later this year, Adams, in collaboration with Claude Lavoie, plans to introduce all-new, water-jacketed, iron and aluminum replacement blocks with siamesed cylinder walls that permit up to 4.310-inch bores. The aluminum casting is a dry-sleeve design that prevents water seepage into the oil pan. All production parts fit, including oil pans, bearings, cranks, and front covers; externally, the blocks retain stock engine-mount provisions and accessory bosses. A 392 deck height is standard, but the decks are thick enough to permit milling to the lower 331/354 height. Four-bolt caps on the center three mains plus added metal in the main web area and lower cylinder walls greatly strengthen these blocks over the old production castings. In place of the original (and much maligned) rear main rope seal, the new blocks will use widely available (and reliable) Ford FE big-block main seals.

Cranks, Bearings, Balancers, and Flywheels

All stock early Hemis had beefy forged cranks and are internally balanced. According to Adams, "Some Chrysler 300 and industrial engine cranks may be nitrided." "The old-school Fueler guys used to make 1,200 to 1,500 hp on stock Hemi cranks back in the day," McKray points out. Although Hot Heads' Walker says he "mags every crank we use--the only bad ones I find are ex-race-car cranks, and they're almost always cracked." McKray finds that the "first failure point will probably be a crack through the mains."

The 331 and 354 cranks physically interchange--they have the same stroke and main- and rod-journal diameters. However, the 331 crank has only -1/4-inch oil-feed holes; for racing, you need to open and chamfer them to the 354's larger 5/16-inch size. The 331/354 cranks won't interchange with the 3.906-inch stroke 392 crank, which has larger main and rod journals. Any of these cranks can turned by as much as 0.040 inch undersize. To maintain adequate strength, McKray cautions, "Be sure to put in a good radius when turning them undersize." Bearing availability was once a problem, but now King Bearings has stepped up and offers good trimetal main and rod bearings in standard and up to 0.040 inch under through selected distributors like Egge and Hot Heads.

You can increase a stock crank's stroke by offset grinding, which moves the rod journal centerlines farther away from the main bearing journal centerlines. The new, reduced-diameter offset journal must be the same size as one used by a different (but still commonly available) rod. On early Hemis, the cam-bore location is so high in the block that rod-to-cam interference with stroker cranks is not a problem as it often is on many small-block engines. On the other hand, it can be hard to find a virgin early Hemi crank that hasn't already been straight-ground severely undersize. Assuming you can find a "good" crank, offset-grinding down to the big-block Chevy's 2.20-inch size and using big-block Chevy-style rods and rod bearings is a popular option. On the 331/354 crank's 2.250-inch mains, this yields about a 0.045-inch stroke increase; with the 392's 2.375-inch journals, about a 0.170-inch increase is achieved. (The "missing" 0.005 inch is a safety factor to allow for journal cleanup.) A 6.75- or 6.800-inch center-to-center rod length is usually a good fit with these combos. The slight 0.006-inch difference between the big-block Chevy 0.990-inch piston pin and Chrysler's 0.984 pin is easily accommodated with a slightly thicker rod pin bushing. Alternatively, you can order your custom pistons for the big-block Chevy pin from the get-go. As can be seen in the table (pg. 82), in the early Hemi's case, a 392 attains significant displacement increases using the big-block Chevy journal size.

Still a problem is the lack of affordable aftermarket cranks. Hot Heads is working on a 4.160-inch-stroke 392 billet crank that with a 4.035-inch bore yields 426 ci. At the top of the food chain there are Sonny Bryant and Crower custom-order Top Fuel–level cranks, but they're priced accordingly. A high-end, custom-order, 5/8-inch stroker on a 0.060-over 392 yields 469 ci, or 529 ci with a 4.310-inch bore in Adams' new thick-wall aftermarket block.

Most stock harmonic dampers are long used up. Even in their day they were prone to failure. Using a Mopar 318/340 small-block's neutral-balanced damper is a practical budget approach; Hot Heads sells converted and indexed 340 dampers that are direct early Hemi bolt-ons. Fluidampr and BHJ offer dedicated, SFI-approved early Hemi balancers.

Hot Heads carries lightweight stock- replacement aluminum flywheels; 146-tooth versions fit '51 to '56 engines, and 172-tooth units fit '57 to '59 engines. Steel and aluminum replacement flywheels are also available from Wilcap.

Where it all Began

Chrysler developed its first Hemi--the 2,500hp XIV-2220 V16 inverted engine--as a potential replacement for Pratt & Whitney's R-2800 radial motor in the World War II P-47 fighter. By the time the engine was ready in 1945, the war was ending, so it did not go into production. Chrysler also collaborated with Continental on the air-cooled AV-17905B V12 hemi-headed engine used in the postwar M47 Patton tank.

Rods and Pistons

All stock early Hemi rods are forged steel with 3/8-inch bolts and come bushed for floating pins. The 331/354 rod length and journal sizes differ from the 392. Properly rebuilt, the rods are OK for most normally aspirated engines. At a minimum, stock rods should be shot-peened and subjected to magnetic-particle inspection, the big ends rebuilt, the small ends rebushed, the beams polished, and the assembly fitted with modern ARP rod bolts (they're the same bolts as those on B/RB Chrysler wedge engines).

Alternatively, you can swap in more modern rods--either production or aftermarket equivalents--with minor mods. Hot Heads will sell you modern rods with the required mods already performed. Remember, alternative rods require rebalancing the engine and in some cases even adding Mallory heavy metal to the crank.

Pontiac 400 rods can be used in a 331/354. Bore the small end to accept the 354 wristpin bushing, drill and chamfer the rod top 1/8 inch for additional pin oiling, and use Pontiac rod bearings.

Some builders create a low-deck 392 by installing the 392 crank in a 354 block. To do this, use 383/400 Chrysler rods and bearings, turn down the 392 crank's main journals to 2.500 inches, resize the thrust surface to the short-deck block's size, and bore the 354 0.062 over.

For a normal, high-deck 392, 440 Chrysler rods work. At 6.76 inches center to center, this 0.200-inch-shorter rod is widely available, inexpensive, and uses a low-cost bearing. The 440 rod has a wider beam, so either the journal must be ground wider or the rod and bearings narrowed about 0.020 inch. Yet another alternative is even stouter 426 Hemi rods with 7/16-inch bolts. Custom pistons with the right compression height and a 1.090-inch pin bore are needed as well.

Then there are aftermarket aluminum billet or forged rods. Bill Miller, GRP, or Venolia can, as Adams puts it, "make an aluminum rod any way you want it." Popular on race cars, street use remains controversial due to aluminum's finite fatigue life. You may have to clearance the oil-pan rails and the bottom of the cylinders to use aluminum rods; be careful not to run into the water passages.

Stock Hemi pistons were cast aluminum. Aftermarket choices run the gamut from stock cast replacement-style (Egge, Hot Heads, Kanter), to Keith Black cast hypereutectic (392 only), to shelf-stock forgings(Arias and Ross), to custom, made-to-order forgings (just about all major piston outfits, but check especially Arias, Hot Heads, JE, Ross, and Venolia).

Walker says early Hemis "really like 10.0:1 compression. They'll run all day on 92-octane gas. With our aluminum heads, you can run more. I'm building an 11.0:1 engine now for the street to prove it." McKray concurs, going as high as 11.0 to 11.5:1 with aluminum heads, "depending on cam timing." For N/A racing on good gas, McKray says, "Go as high as you need it if you can get it on a piston. Sometimes it's hard to run super-high compression due to the Hemi's dome profile." If putting a huffer on it, hold compression down around 8.0 to 8.5:1.

To benefit from the latest and greatest piston-ring technology, it pays to custom-order aftermarket pistons for at least 1/16-1/16-3/16 rings instead of the Hemi's original 5/64-5/64-3/16 ring pack. Ring availability is not a problem for the 392's 4-inch bore (which many other engines share). Even for the oddball 331/354, you can now get high-quality, modern rings from Hot Hemi, Total Seal, and others.

BHJ offers cylinder honing plates. McKray considers them "optional on the street, mandatory for racing." However, Adams says, "The blocks are pretty stiff. The bolts aren't too close to the cylinder wall, and they don't go into water. Plates aren't as critical as they are for some other engines." Preferred honing techniques are pretty much in line with any of today's engines.

The '51 to early-'55 331s used a long, threaded front snout to retain the cam sprocket; '56-and later engines use a short snout with a bolt, a cupped washer, and a thrust plate to retain the cam. All aftermarket cam cores are the late, short-snout style. Short-snout cams and timing sets for '55-and-later low-deck engines can be used to replace earlier long-snout cams.

Cam and Valvetrain

Most early Hemis had hydraulic flat-tappet cams, but some high-perf, marine, and industrial engines had factory solid grinds. The nonadjustable, hydraulic-cam valvetrain parts were different from the adjustable (and rare today) mechanical valvetrain. Special valve covers with bumps were needed to clear the adjustable rockers, making it easy to identify a solid-lifter–equipped engine. Early engines had long-snout cams and unique timing sets that are long gone, but Hot Heads and other early Hemi specialists can convert existing long-snout cams and front ends to use '55-and-later short-snout cams.

All 392 engines take short-snout cams, but because the block's lifter bores are slightly relocated to maintain proper valvetrain geometry on the high-deck block, 392 cams have a slightly different lobe orientation. The 331/354 and 392 cams physically interchange in the block, and the engine will even start up and run, but the timing events won't be right. There's no easy way for the average Joe to tell the difference without degreeing the cam.

High-perf, short-snout cam cores are available, but often the cam itself must be ground to order. Catalog grinds include offerings by Comp (392 hydraulic flat-tappet Thumpr grinds), Crane (early Hemi retrofit hydraulic and mechanical roller cams for both 331/354 and 392 engines), Hot Heads (hydraulic and solid flat-tappet and hydraulic roller cams for all early Hemis), Schneider (solid and hydraulic flat-tappets and solid roller cams), Engle (392 solid roller), and Isky (hydraulic and mechanical flat-tappet cams).

As for specific cam timing, Hemis flow so well on the exhaust side that a dual-pattern cam isn't really needed. For the average performance flat-tappet hydraulic street cam, McKray recommends a grind with about 225 to 230 degrees at 0.050. Add another 10 to 13 degrees on a solid.

An early Hemi hydraulic flat-tappet lifter is similar to the hydraulic lifters specified for the Chrysler LA small-block ('64 to '87 273/318/340/360 non-Magnum) or B/RB big-block wedge ('64 to '78 only). The difference is the early Hemi hydraulic valvetrain pushrod seat has a -1/4-inch ball-seat pushrod tip, but these later lifters have a 5/16-inch ball-seat pushrod tip. Therefore, if early Hemi hydraulic flat-tappet lifters are out of stock (check Hot Heads or Comp Cams), substitute widely available lifters from these specified later engines by changing to custom pushrods with 5/16-inch tips on the lifter ends and (to maintain compatibility with the stock upper valvetrain) -1/4-inch tips at the rocker-arm ends. Likewise, with the right pushrods, solid lifters from specified later engines fit, as will hydraulic or mechanical roller lifter bodies (less the guide links). Crane and Hot Heads sell complete, dedicated early Hemi hydraulic- or mechanical-lifter-paired assemblies complete with the proper links.

For hard-core use, the stock 5/16-inch-od pushrod bodies should be upgraded to 3/8 inch or even larger. This may require opening up the pushrod holes in the heads for clearance. The use of 7/16-inch pushrods with more than 0.850-inch-lift cams for extreme racing may require pushrod sleeves because grinding the necessary clearance excessively thins out the head. Check pushrod-to-head clearance through the entire valve opening/closing cycle, not just statically.

The basic upper valvetrain is OK for street use, but the stock, cast, shaft-mounted rockers will fail under severe use--blowers, max compression ratio, gonzo spring rates, or high-rpm, all-out racing. The exhausts have the most problems and usually fail first. "With more than 0.500 lift, you need to consider an aftermarket exhaust arm," Adams maintains.

Some racers say the nonadjustable hydraulic valvetrain is stronger overall because the mechanical valvetrain's rockers are weaker in the adjuster area. Due to the strength factor and scarcity of stock adjustable-valvetrain parts, for years racers used adjustable pushrods to obtain needed adjustability on the hydraulic valvetrain. specializes in rebuilding and refurbishing Hemi shaft-mounted upper valvetrains (as well as for many other old engines). It can bush the stock rockers and hard-chrome the shafts for severe use. Heavy-duty chrome-moly shafts are also available. Other services include correcting geometry problems, compensating for long valves by reradiusing the rocker tips so the scrub radius moves farther outboard, and even altering the effective rocker ratio beyond the stock 1.5:1. The -1/4-inch pushrod cups in the rockers can be machined to 5/16, eliminating the need for hybrid-tip pushrods when using later Chrysler lifters. Hydraulic valvetrains can be made adjustable without using the rare, stock-style mechanical valvetrain parts (although does stock OE adjusters). Some of these services are available through Hot Heads, too.

For high-end use, adjustable, aluminum roller-rocker shaft-mount valvetrain assemblies are available from Hot Heads,, and T&D. will soon offer a fully rebuildable, high-tech 17-4 investment-cast stainless-steel rocker with an adjustable insert tip that allows easy ratio changes or compensation for valve stem–induced wear.

Complexity or Simplicity?

At first glance, the double-shaft Hemi valvetrain appears overly complicated, but Adams says, "It's the simplest thing you can make. You can pull the heads without pulling the distributor or the headers. Remove 10 bolts and you can lift off both the intake and exhaust rocker shafts and rockers together as an assembly."


The efficient stock oil system needs few mods. One thing to watch for is excessive lifter bore wear. All main bearings except the rear receive oil from the passenger-side lifter gallery. If there is more than 0.0025 inch of lifter-to-bore clearance, the main bearings can become starved for oil. This can be solved by bushing the lifter bores. Shoot for a 0.0005- to 0.0010-inch clearance.

Wear-induced, loose clearances between the rocker arms and shaft allow too much oil upstairs. With only 5/16-inch oil return holes in the heads, the oil pan can be starved. The fix is to ream and bush the rocker arms, then turn and hard-chrome the shafts.

The stock oil pump is adequate. Melling has retooled early 392 Hemi pumps, but they won't fit 331/354s. A modern alternative is a modified 318/340 oil pump. Don't use a standard-volume 318/340 pump; it flows about 15.5 percent less than the standard Hemi unit, while Melling's high-volume 318/340 pump flows about 3.5 percent more.

For a modern, spin-on oil filter, ax the stock filter mount for Hot Heads' 30-degree, up-angle mount or vertical mount. Wilcap has a forward-facing spin-on mount.

Air, Fuel, and Spark

The original factory parts are obsolete for anything other than a straight resto. But thanks to the Hemi's resurgence in popularity, there are plenty of modern aftermarket options.

Intake Manifolds: There was once a heavy factory 2x4 intake for dual Carter AFBs that's said to be worth 50 hp more than the equivalent factory iron single-carb intake--good luck finding one. Offenhauser once offered a slew of multicarb intakes, but nowadays they're swap-meet-only items. Hot Heads offers modern intakes that far surpass any of this old-school stuff, anyway. And there's always EFI .

Ignition: Bolt-in pointless distributors are available from Mallory (Unilite or magnetic-trigger), MSD (Ready-to-Run), and Performance Distributors (drop-in large-cap DUI). Hot Heads offers adapters for installing Chevy V8 distributors. Chrysler 318/340/360 distributors bolt in using longer Hot Heads intermediate shafts. Joe Hunt and Vertex still sell magnetos; Vertex also has a pointless distributor that resembles its traditional magneto on the outside. Pre-'55, 6-volt electrical systems must be upgraded to 12 volts to use a later distributor.

Exhaust: Reputedly, truck manifolds (identified by their four-bolt exhaust pipe mounting flange) are the best factory units, but that's not saying much. For performance, nothing beats tube headers. Hot Heads stocks shorty, universal-block-hugger, full-length-block-hugger, Gasser, and over-chassis styles. Sanderson Headers sells shorties as well as classic-style, full-length Roadster headers. Any premade header requires a Hot Heads adapter plate to fit early 331, small, round-port heads. For fabricators, Hot Heads also sells welded- and bare-flange header kits. Headers By Ed offers exhaust flanges and prebent tubing sections for early Hemis and just about every other engine as well. McKray likes to see 15?8- or 1-3/4-inch primaries into 3-inch collectors for most streetable applications, but for no-compromise power in a 354 race application, Adams specs 2-inch-od x 30-inch primaries into 3-1/2-inch-od x 8- to 10-inch collectors.

Forced Induction: Roots blower kits are available from all the leading supercharger outfits, including Blower Driver Service, Dyer's Blowers, Littlefield, and Mooneyham. Adams says the best early Hemi supercharger manifolds are exclusively available through Hot Heads.

331/354/392 vs. 426

The easiest way to tell early Hemis from a 426: The early Hemi had a rear-mount distributor, an internal oil pump, and a separate valley cover. The 426 Hemis have a front-mount distributor, an external oil pump, and no valley cover with stock intake manifolds.

Primary Sources

We want to specially thank Al Kirschenbaum and Pat Ganahl, along with the following companies that contributed to this article.

Bob McKray Performance; Mission Viejo, CA; 949/458-7087; Early Hemi engine builder and head porter

Gene Adams Performance; Anderson, CA; 530/357-5570: Early Hemi engine builder and racer, new replacement blocks coming soon.

Hilborn Fuel Injection; Aliso Viejo, CA; 949/360-0909; Individual-stack mechanical and electronic fuel injection systems and intakes

Hot Heads Research & Racing Inc.; Lowgap, NC; 336/352-4866; Aluminum heads and your one-stop shop for Chrysler, Dodge, and DeSoto Hemis parts and info (Rocker Arm Specialist); Anderson, CA; 530/378-1075; Shaft-mount valvetrain refurbishing, modification and upgrading; roller rocker systems
Wow! That's a TON of great HEMI information!
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Re: Hot Rod's Early HEMI Guide

Post by scottm »


The Early Hemi Guide Of Death, Part 2 ... es_part_2/
Whether it’s due to the rise of nostalgia drag classes, the growing trend of retro-rods, or just the longing for something unique and different, Chrysler’s first-gen Firepower Hemi V8 engines of the ’50s—the 331, 354, and 392—are undergoing a tremendous upsurge in popularity. As we saw last month in Part 1 of our early Hemi guide, this has led to the development and increasing availability of new parts for the venerable engine. In our first installment, we discussed just about every major Hemi power-making part—except for the one that makes the Hemi a hemi: its unique cylinder-head castings.

We’ll take care of that this month. The early Hemi’s heads were so far ahead of their time in terms of ultimate performance potential when fully ported that they remain competitive with many heads designed for later, more modern engines through at least 1980, about the time engineers started radically raising intake and exhaust ports beyond the original factory profiles. In other words, it took about 25 years for other engines to finally surpass the esteemed Firepower. Read on to find out which early Hemi heads are best, and how they stack up against the competition.

There’s also the “minor” matter of hooking up your back-to-the-future motor to a modern transmission. Old Hemis may be cool, but those original slushboxes behind them sure weren’t. Fortunately, the aftermarket’s got you covered there, too, with adapters to mate most modern transmissions to the old Hemi, even early ’51–’53 models with the cast-in extended bellhousing. We’ve come up with a chart that shows what fits what (page 88).

Another thing no one wants anymore are the old crappo front drives and accessories. They’re heavy, ugly, and obsolete—who runs a generator anymore? And lots of Pro Tourers want air conditioning. No problem. Complete, modern front-drive brackets, pulleys, drive systems, and water-pump adapters are available from sources like Hot Heads.

To get the scoop on heads, we consulted Gene Adams, one of the pioneers of early Hemi development who continues to build and race them to this day, and Bob McKray, another ace Hemi engine builder and head porter. Bob Walker, owner of Hot Heads—a one-stop source for early Chrysler, Dodge, and DeSoto Hemi hot rod parts—gave us the scoop on his aluminum castings, valve covers, and front-drive systems. We also spoke with Wilcap’s Patrick McGuire, the Lord of Transmission Adapters, who can make an adapter for just about anything. And finally, we have the Source List to end all Source Lists (pages 88–89), where we list just about every early Hemi parts source we could come up with.

Get the Lead Out

Efficient Hemis don’t need a lot of ignition lead. Bob Walker says, “Don’t listen to your Chevy buddies. Set initial timing between 8 and 12 degrees. Total timing should be set at 30 degrees at 2,500 rpm, unless a dyno tells you it likes 29 or 31 degrees better.”


As good as they were for their time, all early Hemi heads aren’t created equal. Once you go over 0.500-inch valve lift, it’s time to get serious about head selection. The 392 head is not the best stock casting. True, it does have a larger stock intake valve, but the 392’s intake port entrance is dropped. The heads you really want are from a ’54 to ’55 331—they have tall ports and less restriction in the valveguide area. According to McKray, the ’54 to ’55 331 head also had insert Stellite exhaust valve seats—good for unleaded gas, although not necessarily desirable for racing. This is the only confirmed stock use of insert seats on an early Hemi. Weird, “industrial” heads may exist with the good ports and no exhaust heat riser, but good luck finding them.

Head Identification

Year, Model, CI/Casting NOs.
'51-'53, 331/ 1323333
'54, 331, (also very late '53)/ 1486833
'55, 331,/ 1556157
'56, 354,/ 1619823
'57, 392, (all models and '58 300D)/ 1735282
'58, 392, (Chrysler and Imperial)/ 1731528

You can install 331/354 heads on a 392 block with Hot Heads’ intake port spacers. The 331 heads are also machined for different-sized dowel pins, so they’ll require either fabbing reducer bushings for the heads, enlarging the 392 block deck’s dowel-pin holes, or installing Hot Heads’ stepped dowels. A 392 head can be installed on a 331/354 (though who’d want to?), but (because the engine is narrower and the banks closer together) this requires split or log manifolds typically designed for multi-carb Weber setups or Hilborn stacked injection.

For serious performance, upgrade to larger valves. “The old factory valve job and transition to the port was crappy anyway,” Adams points out. A common upgrade for ’54 to ’56 331/354 heads is the 392’s 2.00-inch intake valve. “The intake is a little larger and with bowl work, you can gain some power,” says Walker.

With higher compression and a big cam, go larger yet. A 2.062/1.800 combo clears even a 331’s small bore and works well for a high-perf street engine. The next common jump is 2.125/1.800, but these won’t clear a 331’s bore. Ultimately, the stock heads can accommodate up to 2.200/1.875 valves with a slight bore notch on the intake side when used on a 4-inch-bore Hemi like a stock 392 (check for head-gasket interference). Compatible valves are available from McKray, and, according to him are “made in a certain length that I know will fit without upsetting the Hemi’s delicate valvetrain geometry.” Other valve sources include Hot Heads, Manley, and Ferrea.

According to the valvetrain specialists at (formerly Rocker Arm Specialist), the key to avoiding wacky geometry on factory Hemi heads is to not use valves that are more than 0.050 inch longer than stock. But deepening the spring pocket to accommodate heavy-duty springs without long valves might result in hitting water, due to the casting’s thinness in this area. If you need gonzo springs, it’s better to machine wider than deeper.

All heads will benefit from porting. As Adams notes, “the ports were rough back then, just terrible.” McKray recommends smoothing the valve seat-to-port transition area, the usual short-turn radius improvements, guide streamlining on both the intake and exhaust ports, and grinding back the pushrod bulge in the intake port. “For all-out heads, remove the bulge and add a pushrod tube,” McKray says. Although the exhaust side is less critical, he says “you can get the exhaust to flow almost as good as the intake. It’s easy to go too far on the exhaust; 65 to 75 percent flow compared with the intake is the sweet spot. You can port a 392 ’til the cows come home and you won’t get over 300 to 325 cfm on the intake side because the guide and bowl area just are not there. By comparison, an all-out 331 head could get up as high as 370 cfm.” McKray and Adams have generated flow numbers for early Hemi heads (see table).

The only current aftermarket alternative to stock iron heads are Hot Heads aluminum castings. The beefy heads have 5⁄8-inch-thick decks and chambers, enlarged pushrod holes, 2.0625/1.80-inch valves, and improved rectangular exhaust ports. They flow better out of the box than any stock 50-year-old head.

In head gaskets, you have a choice of Fel-Pro or Best replacement gaskets and Cometic high-perf MLS gaskets. Head gasket part numbers may vary per model year. Use SCE or equivalent copper gaskets for O-ringed fuel-racing apps. ARP studs are recommended for optimum retention. Hot Heads, Egge, and Kanter have complete overhaul gasket sets. Cometic has 392 top- and bottom-end kits, but the latter doesn’t include a rear main seal.

Cooling and Front-Drives

On ’51 to ’54 cars and most truck, industrial, and marine engines, water exited the block through an intake manifold-mounted thermostat. Starting in 1955, water exited blocks used in passenger cars through front passages in the heads. A separate water manifold connected the two heads to the thermostat. Engines with front-exit water passages received a new (and much lighter) stamped front cover in place of the previous (and very heavy) cast covers. With cast covers, the water pump bolts to the cover; with the stamped covers, the water pump bolts to the block. There were originally three different front cover types: the ’51 to ’54 car and truck heavy cast cover that integrally housed the water pump; a similar cast cover for industrial/marine engines that also covered those blocks’ additional lower water holes; and the ’55 to ’58 car stamped cover.

Hot Heads offers an aluminum early replacement cover that works on both the ’51 to ’54 heavy cast car/truck cover as well as the industrial/marine cover, covering up the latter’s two extra lower holes. It uses a readily available small-block Chevy water pump (Weiand short-style recommended). There are no mechanical fuel-pump mounting provisions, and it must be used with a ’55-and-later short-nose cam. (Cam differences were covered in Part 1, June ’12.)

Other available cooling parts from Hot Heads include a replacement cast aluminum cover for ’55 to ’58 car engines, modern front accessory-drive kits, stock water pumps for ’57 to ’58 engines, and cast aluminum and AN hose–style ’55 to ’58 water crossovers.

Who’s on First?

Hot Rod lore maintains the ’57 Corvette 283ci/283hp fuel-injection engine with a solid cam was the first domestic engine to be rated at 1hp/ci. Guess everyone forgot about the ’57 345ci DeSoto Hemi, which was rated at 345 hp in the ’57 Adventurer with twin, four-barrel carbs and 9.5:1 compression.

Trans Adapters

Frankly, the original Chrysler manual and automatic trannys installed behind early Hemis suck. Parts are nearly extinct, anyway. Hot Heads, TR Waters, and Wilcap have a variety of adapters for bolting up just about any modern Chrysler, Ford, and GM trans (apart from a C4 behind an early Hemi) to short-bell blocks, and, in some cases, the early long-bell blocks as well. Adapters are also available for nostalgia Ford Flathead four-speed and Cadillac LaSalle transmissions, though how long they last behind a built Hemi is anyone’s guess.

For the Chrysler Hemi short-bell blocks, most adapter kits are based around a spacer that replaces the original Chrysler block spacer. The spacer accepts the auto trans or stock bellhousing designed for the new manual trans. A ministarter replaces the original factory starter, and it usually requires a modern spin-on oil-filter mount as well. Flywheels, flexplates, crank adapters, pilot adapters, and miscellaneous parts are added as needed, with the end result that the new transmission’s converter hub and lugs or the input shaft and clutch all end up in the same location as the original design for that trans. Adapters for long-bell blocks are more complex, and on auto transmissions may also require front case and pump mods.

For racing, JW Performance’s SFI-certified Ultra Bell is available for GM Powerglide and TH350/400 automatics, but you have to cut off the front of the transmission case to utilize it. For a direct bolt-on (no adapter plate needed) ’54 to ’58 Hemi SFI-certified manual trans scattershield, contact Browell Bellhousing.

Rocker Covers

A major contributor to the Hemi’s coolness factor is its unique, in-your-face rocker covers.. With spark-plug access directly through the top of the covers, they set the Hemi apart from everyday, run-of-the-mill Wedge-head motors. Over the years, there have been many unique factory and aftermarket covers produced, so you never know what you’ll run into down at the swap meet. As for currently available offerings, Hot Heads and Moon have a wide variety of options.

Sources: Who Makes What For the Early Hemi

We assembled a list of every early Hemi parts source, vendor, and engine builder we could find contact information for. Not listed? Drop us a line at and put “Early Hemi” in the subject line. In the message body, please list your complete contact information: company name, town, state, phone number, and website or email address. We’ll include it in future updates at

Arias Pistons; Gardena, CA; 310/532-9737; Forged pistons

Automotive Racing Products (ARP); Ventura, CA; 800/826-3045 or 805/339-2200; Main and head studs, rod bolts

Best Gasket; Santa Fe Springs, CA; 888/333-2378 or 562/699-6631; Gaskets

BHJ Products Inc.; Newark, CA; 510/797-6780; Harmonic balancers, honing plates

Bill Miller Engineering Ltd. (BME); Carson City, NV; 775/887-1299; Aluminum connecting rods

Blower Drive Service (BDS); Whittier, CA; 562/693-4302; Superchargers

Bob McKray Performance; Mission Viejo, CA; 949/458-7087; Early Hemi engine builder and head porter

Browell Bellhousing; Lafayette, IN; 765/447-2292; SFI-certified ’54–’58 Hemi scattershield

Bryant Racing Inc.; Anaheim, CA; 714/535-2695; Custom billet cranks

Chrisman’s Auto Rod Specialist; Santa Ana CA; 714/850-9224: Hemi engine builder

Cloyes Gear and Products Inc.; Ft. Smith, AR; 479/646-1662; Replacement and True Roller timing sets

Cometic Gasket Inc.; Concord, OH; 800/752-9850 or 440/354-0777; Gaskets

Comp Cams; Memphis, TN; 800/999-0853 or 901/795-2400; 392 hydraulic flat-tappet cams, lifters, kits

Crane Cams; Daytona Beach, FL; 866/388-5120 or 386/310-4875; Hydraulic and mechanical roller cams, lifters, miscellaneous valvetrain parts

Crower Cams & Equipment Co.; San Diego, CA; 619/661-6477; Custom billet cranks

Del West Engineering Inc.; Valencia, CA; 800/990-2779 or 661/295-5700; Custom titanium valves

Dyer’s Blowers; Summit, IL; 708/496-8100; Superchargers

Eagle Specialty Products Inc.; Southaven, MS; 662/796-7373; Steel connecting rods

Ed Iskenderian Racing Cams; Gardena, CA; 323/770-0930; Hydraulic and solid flat-tappet cams

Egge Machine and Speed Shop; Santa Fe Springs, CA; 800/866-3443; Cast pistons, overhaul kits, gaskets

Engle Racing Cams; Long Beach, CA; 562/232-7079; 392 solid roller cams

Federal Mogul (Fel-Pro) Sealed Power; Southfield, MI; 800/325-8886 or 248/354-7700; Gaskets, piston rings, bearings, hydraulic lifters, miscellaneous engine parts

Ferrea Racing Components; Ft. Lauderdale, FL; 888/733-2505 or 954/733-2505; Custom valves

Fluidampr by Horschel Motorsports; Springville, NY; 716/592-1000; Harmonic balancers

Gene Adams Performance; Anderson, CA; 530/357-5570: Early Hemi engine builder and racer, new replacement blocks coming soon

GRP Connecting Rods; Denver, CO; 303/935-7565; Aluminum and titanium connecting rods

Headers By Ed Inc.; Minneapolis, MN; 612/729-2802; Header fabrication parts for do-it-yourselfers

Hemi Haines; Daytona Beach, FL; 386/671-1057; Early Hemi engine builder and parts vendor; lots of buildup-procedure photos on this website

Hilborn Fuel Injection; Aliso Viejo, CA; 949/360-0909; Individual-stack mechanical and electronic fuel injection systems and intakes

Hot Heads Research & Racing Inc.; Lowgap, NC; 336/352-4866; Aluminum heads and your one-stop site for Chrysler, Dodge, and DeSoto Hemi parts and information

Hot Rod Library Inc.; Veyo, UT; 435/574-2174: Publishers of the Complete Chrysler Hemi Engine Manual

J&E Pistons; Huntington Beach, CA; 714/898-9763; Forged pistons

Jeff Johnston’s Billet Fabrication; Nine Mile Falls, WA; 877/4BILLET (orders) or 509/568-0428 (tech); Custom oil pans, valve covers

Joe Hunt Magnetos; Rancho Cordova, CA; 916/635-5387; Magnetos, distributors

JW Performance Transmission Inc.; Rockledge, FL; 321/632-0247; SFI-certified Ultra Bell conversion, GM Powerglide and TH350/400-to-early Hemi

K1 Technologies; Mentor, OH; 440/497-3100; Steel connecting rods

Kanter Auto Products; Boonton, NJ; 800/526-1096 or 973/334-9575; Pistons, overhaul kits

KB Performance Pistons (United Engine and Machine Co.); Carson City, NV; 800/648-7970 or 775/882-7790:; 392 cast hypereutectic pistons

King Engine Bearings Inc.; Cedar Grove, NJ; 800/772-3670 or 973/857-0705; Bearings

Littlefield Blowers; Anaheim, CA; 714/992-9292; Superchargers

Lock-N-Stitch Inc.; Turlock, CA; 800/736-8261 or 209/632-2345; Lock-N-Stitch crack repair technology

Mallory Ignition Div., Prestolite Performance; Cleveland, OH: 216/688-8300; Distributors

Manley Performance Products Inc.; Lakewood, NJ; 732/905-3366; Custom valves

Melling Engine Parts; Jackson, MI; 517/787-8172; Oil pumps, oil pump intermediate shaft, timing chains, hydraulic lifters, valvesprings

Milodon Inc.; Simi Valley, CA; 805/577-5950; Oil pumps, gear drives, angled main caps, roller timing chain, head and main studs

Mooneyes USA (Moon Equipment Co.); Santa Fe Springs, CA; 800/547-5422 or 562/944-6311; Valve covers, valley covers, oil filter adapters and block-offs

Mooneyham Blowers; Ontario, CA; 909/984-3000; Superchargers

MSD Ignition; El Paso, TX; 915/857-5200 (general) or 915/855-7123 (tech); Distributors

O’Brien Truckers: Charlton, MA; 508/248-1555; Finned valve covers, spark-plug wire covers, valley covers

Performance Distributors; Memphis, TN; 901/396-5782; Distributors

Pro-Gram Engineering; Barberton, OH; 330/745-1004; Billet main caps (Rocker Arm Specialist); Anderson, CA; 530/378-1075; Refurbishing and modification of shaft-mount rocker arm systems; early Hemi roller rocker setups

Ross Racing Pistons; El Segundo, CA; 800/392-7677 (orders) or 310/536-0100 (tech); Forged pistons

Roto-Faze Ignitions and Equipment; Torrance, CA; 310/325-8844; Custom-made distributors, con-rods, blower manifolds

Sanderson Headers; S. San Francisco, CA; 800/669-2430 or 650/583-6617; Headers

SCAT Enterprises Inc.; Redondo Beach, CA; 310/370-5501; Steel connecting rods

SCE Gaskets Inc.; Lancaster, CA; 661/728-9200; Gaskets

Schneider Racing Cams; San Diego, CA; 619/297-0227; Solid and hydraulic flat-tappet cams; solid roller cams

Smith Bros. Pushrods; Bend, OR; 800/367-1533 or 541/388-8188; Custom pushrods

Stef’s Performance Products; Lakewood, NJ; 732/367-8700; Drag-race oil pan

T&D Machine Products; Carson City, NV; 775/884-2292; Racing shaft-mount roller rocker systems

Total Seal Inc.; Phoenix, AZ; 800/874-2753 (orders) or 623/587-7400 (tech); Piston rings

TR Waters; Vermont; 802/883-5518; Transmission adaptors; valley cover; rocker shaft collars; main cap girdle; stepped crank key; front motor plates

Venolia Pistons and Rods; Long Beach, CA; 562/531-8463 or 323/531-8463; Forged pistons, aluminum rods

Vertex Magneto—Taylor Cable Products Inc.; Grandview, MO; 816/765-5011; Magnetos, distributors that resemble a magneto, spark plug wire sets

Weiand (A Division of Holley); Bowling Green, KY; 800/HOLLEY-1 ext. 8530 (nearest dealer) or 270/781-9741 (tech); 2x4 intake manifold

Wilcap Co.; Pismo Beach, CA; 805/481-7639; Transmission adaptors, flywheels, oil filter adaptors
Posts: 390
Joined: Fri Dec 14, 2001 6:00 pm
Location: Vermont

Re: Hot Rod's Early HEMI Guide

Post by TrWaters »

I did email the magazine to correct my address and phone number. :lol:
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.
Posts: 665
Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: Hot Rod's Early HEMI Guide

Post by George »

Looks like they forgot Quality Engineered Components.
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