Mopar 426 Wedge Engine Specs

Intro

➤ See the Family Page for specs common to all engines in this family.

The Mopar 426 wedge is the engine condemned to spend eternity answering the same stupid question: “Is that a Hemi?” No. Chrysler built a perfectly legitimate 426-cubic-inch RB wedge before the Elephant arrived, and in Max Wedge form it was already terrorizing drag strips while the Hemi engineers were still getting ready to steal everybody’s attention. Same 426 cubic inches. Entirely different engine. The sooner that gets settled, the sooner the interesting part of the story can begin.

The 426 wedge grew directly out of the 413 RB. Chrysler kept the raised-deck architecture and the same 3.750-inch stroke, then opened the bore from 4.1875 to 4.250 inches. That produced 426 cubic inches without rewriting the whole engine. Chrysler had already built a good tall-deck wedge; more bore gave it more displacement and more room to breathe. Sometimes engine development really is that sensible.

What Chrysler did with those 426 inches is where the personality splits. The ordinary Street Wedge was a strong big-block meant to move real cars on real roads without acting like every stoplight was eliminations. In the right Dodge, Plymouth, or Chrysler it delivered the kind of big-cube torque an RB was supposed to deliver. There is no shame in that version unless somebody has spent too much time believing every old Mopar needs a racing résumé.

The Max Wedge was another animal altogether. For 1963 Chrysler took the Maximum Performance program that had started with the 413 and gave it the larger 426 bore. Cross-ram dual four-barrels, special heads, serious compression, aggressive cam timing, big exhaust, and factory Super Stock intent turned the wedge into something built to settle arguments a quarter-mile at a time.

The 1964 Stage III version pushed that program to its final factory development before the 426 Hemi walked in and permanently changed the conversation. That does not make the Max Wedge some unfinished Hemi rehearsal. It was one of Chrysler’s nastiest wedge packages in its own right, and it earned that reputation before hemispherical heads started collecting all the trophies in people’s memories.

Naturally, rarity and reputation have encouraged every ordinary 426 wedge to consider applying for a promotion. A four-barrel engine becomes “probably Max Wedge.” A cross-ram added forty years later becomes “factory.” A block with the right displacement becomes Super Stock history sometime between the estate sale and the internet listing. None of that survives contact with heads, stampings, dates, bore notches, induction, exhaust, vehicle application, and documentation.

That proof is especially important because Street Wedge and Max Wedge hardware can share enough family resemblance to encourage optimism. A correct Street Wedge can be a valuable and desirable engine without pretending it spent weekends at the drag strip. A real Max Wedge deserves considerably more attention because the complete factory package is the history, not merely the number cast into somebody’s imagination.

For a modern street build chosen from loose engines, the 426 wedge can be harder to justify than a 440. The 440 gives more displacement, broader parts familiarity, and an easier path to big street torque. But that is a garage-building argument, not a historical one. A correct 426 car, a genuine Max Wedge, a Stage III engine, or a proper period build has a reason to keep the 426 exactly where Chrysler put it.

So quit apologizing for the wedge because it is not a Hemi. The 426 RB had already earned serious factory performance credentials before the Elephant took over. Respect the Street Wedge for its actual job, make a Max Wedge prove its expensive claims, and remember the only thing the wedge and Hemi automatically share is 426 cubic inches. Around Mopars, that number has been starting arguments longer than most of us have been alive.

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Overview

Chrysler created the 426 wedge by doing exactly what it had done to create the RB family in the first place: keep the useful architecture and add displacement where there was room for it. The 413 already used the raised-deck block and 3.750-inch stroke. For 1963 Chrysler opened the bore to 4.250 inches and landed at 426 cubic inches. No new religion was required. Just more cylinder.

The basic RB hardware stayed familiar: roughly 10.725-inch deck height, 4.800-inch bore spacing, 6.768-inch connecting rods, five main bearings, in-block camshaft, pushrod valvetrain, shaft-mounted rockers, and conventional Chrysler wedge heads. That last item deserves repeating because the displacement number has confused enough people already. Wedge heads. Not Hemi heads.

The later 426 Hemi happens to use the same nominal 4.250-inch bore and 3.750-inch stroke. That is an interesting coincidence of displacement strategy, not evidence that the engines are mechanically interchangeable. The Hemi brings hemispherical chambers, enormous heads, different pistons, different valvetrain, different intake and exhaust hardware, and its own block details. Two engines can sweep the same cubic inches without sharing a personality any more than two men wearing size-ten boots share a Social Security number.

The 426 wedge first became important through Chrysler’s Maximum Performance program. The 413 Max Wedge had shown in 1962 that Chrysler could turn the RB architecture into a genuine factory drag engine. Enlarging it to 426 for 1963 gave the program more bore without surrendering the familiar 3.750-inch stroke, and Chrysler immediately put the additional cubes to work in Dodge and Plymouth Super Stock machinery.

The Max Wedge package was not one magic part. It was a combination, which seems obvious until somebody tries to authenticate one by pointing at the intake manifold. Chrysler used high-flow heads, dual four-barrels on cross-ram induction, aggressive cam timing, serious exhaust manifolds, high compression, and the supporting hardware needed to make the whole mess useful at wide-open throttle. A factory performance engine is generally what happens when all the parts receive the same memo.

Dodge Ramcharger and Plymouth Super Stock versions carried that hardware into cars whose purpose was considerably clearer than their street registration might suggest. These were not luxury cars accidentally equipped with too much carburetor. The engine, transmission, rear axle, body and chassis package were aimed at drag racing, and everyday manners were allowed to stand over in the corner until somebody needed them.

The 1963 426 Max Wedge therefore deserves its reputation, but reputation is precisely why identification needs discipline. A regular 426 RB block with a cross-ram bolted on later remains a regular block with an interesting intake until the rest of the evidence arrives. Heads, block details, pad stamping, dates, carburetors, exhaust, compression, vehicle application, drivetrain, and documentation all help establish whether the engine came from Chrysler as the expensive version somebody is now selling.

For 1964 Chrysler developed the wedge program into the Stage III Max Wedge. This was the final sharpened factory version of the Maximum Performance wedge before the 426 Hemi took over the headline job. Stage III was not decorative nomenclature. It represented a specific late Max Wedge combination, and applying the name casually to any 1964 426 wedge is how historically useful terminology becomes classified-ad seasoning.

The Stage III package continued the same general mission: heads, cross-ram induction, carburetion, camshaft, compression, exhaust, and Super Stock-oriented hardware selected around racing rather than comfortable transportation. Chrysler was squeezing the last serious factory competition performance out of its wedge architecture, not trying to make the dealership demonstrator easier to parallel park.

The Hemi’s arrival tends to make this part of the story look like an evolutionary dead end. That is hindsight talking. The Max Wedge had already been successful enough to establish Chrysler as a serious factory drag-racing player. The Hemi became the next weapon because Chrysler wanted more, not because the wedge had somehow failed to participate.

Alongside all that race hardware were ordinary Street Wedge 426s, and those engines need to remain ordinary without being insulted for it. A Street Wedge used the same displacement and RB architecture but carried a much calmer combination intended for regular production use. Less race hardware does not equal defective engine. It means Chrysler expected the owner to spend more time on public roads than staging lanes.

That distinction matters because some castings crossed between Street Wedge and Max Wedge use. One block casting therefore may not settle the argument. Original Max Wedge blocks can show useful clues such as factory cylinder-bore relief notches for large exhaust valves, along with appropriate Maximum Performance pad markings and supporting hardware. Each clue strengthens the case. None should be asked to perform the entire trial by itself.

This is one of those engines where completeness can become more valuable than the bare block. Max Wedge heads, cross-ram intake, correct carburetors, exhaust manifolds, linkage, air cleaners, distributor, brackets, and other specialized pieces can turn a stripped bargain into a very long scavenger hunt. Rare factory performance packages have a nasty habit of losing the cheapest-looking part first and making that part expensive forever afterward.

Race history complicates the picture further. Genuine competition engines were not museum displays. They were bored, repaired, sleeved, re-cammed, re-headed, re-intaked, and occasionally blown to pieces by people whose main concern was making the next round. A documented race engine can remain historically important after repairs. An undocumented cracked block with a cross-ram and a dramatic story is merely damaged merchandise with good public relations.

A used 426 wedge therefore deserves the same cold inspection as any other expensive old engine. Check the casting, identification pad, bore, crank, heads, deck, main webs, lifter bores, previous sleeves, thread repairs, intake, carburetion, exhaust, and evidence of previous machine work. Orange paint remains one of the least effective crack-detection methods ever developed.

Mechanically, the 426 sits neatly between its RB siblings. The 413 uses a 4.1875-inch bore. The 426 opens that to 4.250. The 440 eventually takes it to 4.320. All retain the same nominal 3.750-inch stroke. That makes the 426 the middle bore size rather than some strange offshoot of the family.

Compared with the 413, the 426 simply starts with more cylinder diameter and twenty-three more cubic inches. In Max Wedge history, it also represents the more developed phase of Chrysler’s early factory drag program. The 413 established the idea. The 426 gave it more room and carried it into the Stage III era.

Compared with the 440, the 426 is rarer and much more tightly tied to a short, specific period of Chrysler performance history. The 440’s additional displacement, broader production base, and familiar street combinations usually make it the more sensible engine when somebody is building from scratch. Sensible and historically correct are not always invited to the same meeting.

That is why converting a genuine Max Wedge into a generic modern street engine can be a particularly efficient way to spend money while reducing historical interest. If the special pieces and documentation survive, preserve the combination. Modern performance can be built from vastly more ordinary RB iron. Chrysler is not making replacement 1964 history.

A standard 426 wedge is another matter. With sensible compression, appropriate heads, a street camshaft, good induction, free exhaust, proper ignition, cooling, gearing, and converter or clutch selection, it can make a thoroughly satisfying big-block street engine. It does not need Max Wedge cosplay to make torque.

The engine’s real problem has always been the number stamped on its résumé. Say “426” and everybody expects hemispherical heads or Super Stock provenance. The ordinary wedge gets overlooked, while questionable engines get promoted. Both reactions miss the point.

The 426 RB wedge was a strong production big block and, in Max Wedge form, one of Chrysler’s genuine factory drag-racing weapons. The Street Wedge deserves to remain a Street Wedge. The Max Wedge deserves proof and preservation. And the Hemi can keep its own valve covers. The wedge already earned enough history without borrowing any.

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General Specs

Displacement	426 cu in / 7.0L	Bore / Stroke	4.250 in × 3.750 in
Production / Use Era	1963–1965 Mopar RB-series wedge and Max Wedge performance era	Bore Spacing	4.800 in
Engine Family	Chrysler / Mopar RB-series raised-deck big-block wedge V8	Deck Height	10.725 in
Block Material	Cast iron	Rod Length	6.768 in
Cylinder Head Material	Cast iron	Main Journal	2.750 in
Fuel / Induction	Gasoline; carbureted, single 4-barrel or cross-ram dual-quad by version	Rod Journal	2.375 in
Cam Location	In-block camshaft	Main Bearings	5
Valve Layout	OHV / pushrod, 2 valves per cylinder	Firing Order	1-8-4-3-6-5-7-2
Common Main Caps	2-bolt	Distributor Rotation	Counterclockwise
Rear Main Seal	2-piece	Weight	~670–720 lb complete iron RB big-block, depending on accessories/configuration
Balance	Internal balance	Dimensions	~30H / ~29W / ~32L

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Variants

The Mopar 426 RB wedge needs a variant map with guardrails, because the number 426 has been causing bad decisions since before most of these cars had their second set of tires. There are really four lanes that matter: standard / Street Wedge 426s, 1963 426 Max Wedge engines, 1964 Stage III Max Wedge engines, and service, replacement, race, or clone confusion. Mix those together and the page turns into an auction listing with a flashlight under its chin.

The important split isn’t just displacement. It’s purpose, hardware, proof, and value. A standard 426 wedge can be a strong RB big block. A real Max Wedge can be serious factory drag-racing history. A Stage III car can be even sharper. A tribute, replacement engine, or loose parts pile can still be useful, but it doesn’t get to wear factory Super Stock money because somebody said “426” loud enough.

Standard / Street Wedge 426s

The standard 426 wedge was Chrysler’s raised-deck RB wedge engine using a 4.250-inch bore and 3.750-inch stroke. It shared the magic displacement number with the later 426 Hemi, but that’s where the lazy comparison needs to stop before it trips over the cylinder heads. This engine used wedge heads, RB architecture, and ordinary big-block logic, not Hemi hardware wearing cheaper valve covers.

Street Wedge 426s gave Chrysler, Dodge, and Plymouth buyers big RB torque without the full Max Wedge race package. In the right car, that still makes a strong, desirable engine. It can pull hard, look right, and carry early-1960s Mopar weight with authority. It just isn’t automatically a factory drag-strip engine because the displacement badge makes people stand up straighter.

That matters when money enters the room. A correct Street Wedge deserves respect and sane value. It doesn’t deserve Max Wedge money unless the parts and paperwork prove Max Wedge identity. The block, heads, intake, carburetion, exhaust, compression, camshaft, date codes, application, and vehicle history all need to agree. A seller’s confidence isn’t documentation. It’s just noise with a price tag.

1963 426 Max Wedge Engines

The 1963 426 Max Wedge is where the 426 wedge became a factory drag-racing weapon instead of just a strong RB big block. Chrysler enlarged the Max Wedge idea from the 413 to 426 cubic inches and aimed it at Super Stock work, with Dodge Ramcharger and Plymouth Super Stock versions carrying the fight into cars that weren’t built for quiet Sunday manners.

This package had real hardware behind the name: dual four-barrels on cross-ram induction, special high-flow heads, serious exhaust manifolds, aggressive camshaft, high-compression options, and application details that separated it from ordinary production wedges. That’s why the claim is valuable. It’s also why the claim attracts creative storytelling from people who think a cross-ram intake can baptize a whole engine.

A real 1963 Max Wedge claim has to be proven as a package. Block, heads, intake, carburetors, exhaust manifolds, compression, camshaft, date context, vehicle application, transmission, rear axle, tags, paperwork, and history all matter. A regular 426 wedge with a few scary-looking parts doesn’t get to sneak into the Max Wedge club through the service entrance.

1964 Stage III Max Wedge Engines

The 1964 Stage III Max Wedge was the final factory Max Wedge chapter before the 426 Hemi took the spotlight and started eating every conversation in the room. Stage III isn’t just a fancy phrase to sprinkle on any 426 wedge. It belongs to a specific late Max Wedge package, and the year, hardware, and application have to support it.

The Stage III package carried the wedge program to its most developed factory form. The induction, heads, exhaust, compression choices, camshaft, and Super Stock purpose all pointed in the same direction. This wasn’t a polite street engine with a gym membership. It was Chrysler wringing the last hard factory drag-strip work out of the wedge before the Hemi moved in with bigger lungs and worse manners.

That makes proof even more important. Stage III value lives in the correct pieces and the correct context. Intake, carburetors, heads, exhaust manifolds, camshaft, compression, block details, date codes, body application, and paperwork all have to line up. If the parts are missing, mixed, reproduced without disclosure, or backed only by a story, the price needs to come down before the buyer needs oxygen.

Service, Replacement, Race, and Clone Confusion

The 426 wedge has lived long enough to collect service blocks, replacement engines, race rebuilds, restamps, tribute cars, Max Wedge-style builds, and plain old mystery swaps. Some of those are useful. Some are valuable. Some are fun. Some are trouble wearing orange paint. The Geezer doesn’t care how good the story sounds until the parts start proving it.

A service-replacement 426 wedge can be a good engine, especially if it’s complete and honestly described. A Max Wedge-style clone can be a nasty driver. A tribute car can be a fine way to enjoy the look and sound without pretending history came in the trunk. None of that automatically makes the engine born-with, factory Max Wedge, Stage III, or Super Stock documented.

Race history cuts both ways. A raced engine may carry real period value, or it may carry cracks, sleeves, welded repairs, worn lifter bores, damaged threads, patched decks, and machine work that looks like it lost a bar fight. Pay for documented history, not just abuse with a better nickname.

The right variant question isn’t “is it a 426?” That’s the first inch of the driveway. The real question is which 426 wedge, with which heads, induction, exhaust, compression, camshaft, block details, date codes, vehicle context, and paperwork. That answer decides whether the engine is a standard Street Wedge, a real 1963 Max Wedge, a 1964 Stage III prize, a service replacement, or a clone borrowing thunder from the expensive side of the room.

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Key Notes

The Mopar 426 wedge is the RB engine that gets shoved into the shadow of the 426 Hemi so hard people forget it had a real job of its own. That’s the first thing to fix. This isn’t the Elephant, isn’t a low-deck B engine, and isn’t just a 413 with a little more gossip. It’s a raised-deck wedge big block with serious factory performance history and a bad habit of being misidentified by people who only hear the number 426.

The basic fingerprint is 4.250-inch bore and 3.750-inch stroke in Chrysler’s RB architecture. That puts it above the 413 by bore size while keeping the same stroke, and below the 440 by displacement. That sounds simple until somebody tries to order parts by family rumor instead of measurements. Bore, heads, pistons, compression, induction, and application decide what the engine really is.

The first separation is 426 wedge versus 426 Hemi. They share displacement, but the heads, pistons, valvetrain, induction, exhaust, block details, fitment, price, and mythology split immediately. A wedge can be important and valuable, but it doesn’t get Hemi money just because the cubic inches match. The heads have to do their own talking.

The second separation is standard 426 wedge versus Max Wedge. A normal Street Wedge can be a fine engine, but the Max Wedge was a specific factory performance package with special heads, cross-ram intake, dual carburetors, serious exhaust, compression, camshaft, and application context. A plain 426 with a four-barrel and a seller who says “Super Stock” twice isn’t proof. It’s theater until the hardware backs it up.

The 1963 and 1964 Max Wedge details need their own caution. The 1963 426 Max Wedge carried the enlarged Max Wedge fight forward from the 413. The 1964 Stage III was the final developed factory wedge chapter before the Hemi took over the spotlight. Those labels have meaning, but they also attract lazy ads. Stage language without matching parts, dates, application, and documentation is just expensive seasoning on a weak stew.

The 426 wedge also needs separation from the 413 and 440. All three live in the RB neighborhood and use the 3.750-inch stroke, but bore size, displacement, pistons, compression math, value, and performance history aren’t the same. The 440 usually wins the easy street-build argument because parts familiarity is stronger and recipes are everywhere. The 426 wedge wins when correctness, rarity, Max Wedge history, or the original car’s identity matters.

B-series and RB-series separation still matters before the parts counter gets involved. The 426 wedge is a raised-deck RB engine, not a low-deck 361, 383, or 400. Intake width, valley fit, deck height, piston compression height, pushrods, brackets, swap fit, and some top-end expectations change. “Big-block Mopar” isn’t a parts number. It’s the warning label before measuring starts.

Completeness can change value faster than horsepower talk. A correct block matters, but Max Wedge heads, cross-ram intake, carburetors, exhaust manifolds, linkage, air cleaners, distributor, brackets, pulleys, oil pan, date-correct hardware, and vehicle documentation can make or break the economics. A bare block can be worth saving. A complete proven package is where the serious money usually hides.

A used 426 wedge needs inspection before excitement. These engines have been raced, swapped, rebuilt, overbored, cloned, patched, and misidentified for decades. Check casting numbers, pad stamping, bore size, crank, heads, intake, carburetors, exhaust pieces, date codes, vehicle application, previous machine work, cracks, sleeves, main-web condition, deck surface, and thread repairs. Orange paint doesn’t heal bad iron.

Race history has to earn its keep. A documented race engine can carry real value. An undocumented abused engine can carry cracks, wear, missing parts, and a story trying to outrun the machine shop bill. Don’t pay extra for “drag history” unless the evidence is better than tire smoke and family legend.

Build judgment depends on the goal. A documented Max Wedge or Stage III engine belongs in preservation or correct restoration unless the owner enjoys setting money on fire. A standard 426 wedge can be a strong old-school street RB with the right compression, heads, cam, induction, exhaust, ignition, cooling, converter or clutch, and gear. A mystery core should be inspected before anyone starts planning hero numbers.

The 426 wedge doesn’t need to pretend it’s a Hemi to matter. It was part of Chrysler’s real raised-deck performance story before the Elephant swallowed the spotlight. Verify the RB identity, wedge configuration, bore, stroke, heads, induction, exhaust, dates, application, documentation, and block condition before spending serious money. The number 426 opens the conversation. It doesn’t finish the argument.

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Bottom Line

The Mopar 426 RB wedge deserves better than spending eternity explaining that it is not a Hemi. It is Chrysler’s raised-deck wedge-head 426, and in Max Wedge form it was already serious factory drag-racing hardware before the Elephant stole the spotlight. The Hemi became the household name. That does not turn the wedge into a consolation prize.

The first split that matters is Street Wedge versus genuine Max Wedge. A standard 426 wedge can be a strong, interesting, correct engine for the right early-1960s Mopar. A real 1963 Max Wedge or 1964 Stage III engine belongs in a different conversation entirely because the heads, induction, exhaust, compression, camshaft, application, and documentation give it real factory-performance significance. Same displacement does not mean same engine value just because the seller says “426” slowly.

The 426 wedge makes its strongest argument when correctness or period identity matters. A documented Max Wedge car, proper Street Wedge restoration, period Super Stock build, or historically appropriate RB project gives the engine a reason to be there. In those cases, swapping in a 440 because it is easier can solve the horsepower question while weakening the reason the car was interesting in the first place.

As a loose engine chosen strictly for performance, the argument gets narrower. A 440 usually offers the easier route to big street torque, and a 400 low-deck stroker may make more sense for a modern performance build. That does not make the 426 wedge weak. It means rare-engine money should buy something more than the privilege of using harder-to-find parts when originality and history are not part of the job.

So respect a real Street Wedge for what it is, preserve a genuine Max Wedge when the evidence supports it, and refuse to let the number 426 write checks the hardware cannot cash. It is not a Hemi, not automatically a Max Wedge, and not magically valuable because the displacement happens to share famous company. Buy the engine that is actually there. Around Mopar 426s, the wrong assumption can cost more than the right engine.

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