Best 440 Mopar Stroker Kit — 496 vs 512 vs 528

TL;DR: A 440 stroker kit is really a crankshaft decision — 496, 512 and 528 are three stroke-and-bore combinations built on the same RB block, using 4.150", 4.250" and 4.375" strokes respectively. The number on the box already assumes an overbore you may not be able to run: 512 and 528 both assume roughly .060" over, and if your block only sonic-checks safe at .030" you will not land on the advertised displacement. Choose 496 for a pump-gas street car on a block you would rather not push, 512 for the best all-round street/strip combination, and 528 when you have a good block, a deep budget and a car heavy enough to use it. Everything downstream — rod length, compression height, dish volume, balance, pan clearance — follows from that one choice, so make it first and make it once.

If you searched "440 stroker kit," you have probably found three kits that look nearly identical and differ mainly by the number printed on them. This guide is about what actually separates them, and about the two questions that decide whether the kit you order will fit the engine you own.

What 496, 512 and 528 actually mean

A stock 440 RB is a 4.320" bore with a 3.750" stroke, which works out to 439.7 cubic inches. Every stroker number you see is that same block with a longer-stroke crank and some amount of overbore. The arithmetic is not negotiable:

Read that table twice, because it is the most useful thing on this page. The displacement on the box is the crank's stroke plus an assumed overbore. The same 4.150" crankshaft gets sold as a 493, a 496 and a 500 depending on which bore the vendor assumed. The same 4.250" crank is a 505 or a 512. Nobody is lying — they are quoting a finished combination, and the bore half of that combination belongs to your block, not to their crank.

So the practical version of "which kit" is: pick a stroke, find out what bore your block will safely take, then find out what you actually built.

Shop the platform: Mopar RB big block parts · Rotating assemblies

Your block decides more than the crank does

Before you spend anything, the block has to be measured. RB castings vary a great deal, and the later 1970s blocks in particular have a reputation for thinner and less concentric cylinder walls than the mid-'60s pieces. Three things to establish:

1. Sonic check the cylinders. This costs an hour at a machine shop and it is the only honest answer to "can I go .060 over?" You want meaningful wall thickness left on the thrust side after the finish bore — there is a commonly quoted street minimum, with less tolerated on a mild engine and more wanted on anything boosted or sprayed — but ask your machinist for their own minimum; shops differ, and their number governs. A block that will not take .060" does not disqualify a 4.250" or 4.375" crank — it just means you build a 505 or a 520 instead of a 512 or a 528, with identical parts.

2. Confirm it is an RB, not a B. The RB (raised block) family — 383 RB, 413, 426 Wedge, 440 — uses a 10.725" deck height. The low-deck B family — 383 B, 400 — uses 9.980". They share a bore family and a lot of parts, but not compression height, not pushrod length, and not intake manifolds. A 440 crank does not belong in a 400, and every compression height in this guide is an RB number.

3. Plan on clearancing. A 4.375" crank swings the rod bolts and counterweights into places the factory never intended. Expect to grind the pan rails and the bottoms of the cylinder bores for rod-bolt clearance, and to check the counterweights against the camshaft and the oil pump pickup. A 4.150" crank in a 440 is close to a drop-in; a 4.375" is a machining job. Budget the labor, not just the parts.

Choosing between the three

Here is the comparison, assuming a .060"-over block so the three line up directly:

A few things that table implies but does not say outright:

Bigger stroke is not free rpm. Mean piston speed rises with stroke, and 4,375 fpm at six grand is genuinely into "this is a torque engine" territory. A 528 is not the choice for a car that wants to rev; it is the choice for a heavy B-body that wants to pull from just off idle.

Rod ratio matters less than the internet says; compression height matters more. As stroke grows, the piston gets shorter to fit under the same deck. A 1.778" compression height piston puts the top ring closer to the crown and leaves less skirt for stability. It works — thousands of 528s run — but it is a real reason to buy a good piston rather than the cheapest one in the kit.

The 512 is the default for a reason. It gets nearly all of the 528's torque, needs less clearancing, and keeps piston speed and compression height in comfortable territory. Without a specific reason to go longer or shorter, build the 512.

→ Pistons · Rings · Bearings

Compression: where most 440 stroker builds go wrong

Adding 60-90 cubic inches under a set of 84cc heads raises compression whether you planned for it or not. Worked estimates below assume an 84cc chamber, a .039" compressed head gasket and .010" deck clearance:

Those are planning estimates, not ordering specs — your actual deck clearance, gasket thickness and dish volume set the real number, and all three should be measured at mockup. But the shape of the answer is stable: a big-inch RB on pump gas wants a dished piston, and the dish has to grow as the stroke grows if you want to hold the same ratio. Flat-tops belong in a 496 with aluminum heads and good fuel, or in a race engine.

The corollary: buy your heads and your pistons as one decision. A large-runner aluminum head with a small chamber and a flat-top piston is an E85-or-race-gas combination whether the box says so or not.

→ Cylinder heads · Gaskets and seals

Balance: the step people find out about late

The factory 440 is externally balanced — the damper and the flexplate or flywheel carry counterweight, and a bare crank spun without them is meaningless. Most aftermarket stroker cranks are offered internally balanced, with heavy metal in the counterweights doing that work instead.

That is usually the better engineering answer, and it carries three consequences:

• You need a neutral-balance damper and a neutral-balance flexplate or flywheel. Factory weighted pieces will not work on an internally balanced crank.
• The assembly must be balanced as a set — crank, rods, pistons, pins, rings, bearings — at a shop, with your actual parts. Not optional on a stroker, and not something a kit can do in advance.
• Confirm the rod journal size before ordering rods. Many aftermarket RB stroker cranks are cut with a big-block Chevy 2.200" rod journal instead of the Mopar 2.375", specifically because BBC rods and bearings are cheaper and more available. Both are correct; they are not interchangeable, and your bearing order depends on which one you bought — check the crank part number.

Also confirm the main journal spec. Some cranks are sized to the factory 2.750" RB main and some are offered in alternate sizes for a particular block prep. Order bearings after the crank is in your hands and measured, not before.

→ Bearings · Oil pumps and pans

Crank tiers — what you are actually paying for

The forged 4340 RB stroker cranks we carry cover a real capability spread. Every one of them is a forged 4340 piece; the differences are in the forging, the finishing and the intended power level.

Our RB stroker crankshaft listings cover all three strokes in every one of those brands — Scat, Eagle, Callies Magnum, K1 and Molnar — which is the full practical selection for a 440-based build. Advertised ceilings vary by manufacturer and by how the engine is used; treat that last column as a shopping bracket, not a rating.

One catalog note, stated plainly: we currently list RB stroker crankshafts, standard-bore 440 pistons, rings and bearings, but not big-block Mopar connecting rods or stroker-specific compression-height pistons. Until those land, a 440 stroker built from this catalog is a crank-plus-support-parts purchase, not a complete rotating assembly. Better to say so up front than to sell you two-thirds of a kit.

→ Rotating assemblies · Camshafts · Intake manifolds

The ordering checklist

Work this in order. Each step depends on the one above it.

1. Sonic check the block. Record the safe finish bore.
2. Pick the stroke — 4.150", 4.250" or 4.375" — on the use case, not the biggest number.
3. Compute the real displacement from your bore and that stroke. Write it down; it is what you built, regardless of the kit's name.
4. Confirm rod journal size (Mopar 2.375" vs BBC 2.200") and main journal spec on the specific crank part number.
5. Choose the rod length, then let the deck math set the piston compression height: CH = 10.725 − (stroke ÷ 2) − rod length.
6. Choose the dish volume to land on your target compression against your actual chamber cc and gasket thickness.
7. Order the damper and flexplate/flywheel to match the balance type — neutral for an internally balanced crank.
8. Mock up and clearance: rod bolt to pan rail and cylinder bore, counterweight to camshaft, counterweight to oil pump pickup.
9. Balance the assembly with the real parts.
10. Then buy the cam, and match it to the finished displacement rather than to "440."

FAQ

Is a 440 stroker kit worth it over just rebuilding the 440? If the block needs boring anyway, the incremental cost of the stroker crank and matching pistons buys 55-90 cubic inches you keep forever, and cubic inches are the cheapest torque available on this platform. If the engine is healthy and you only want a bit more, a cam, heads and intake on the stock 440 is the better value.

Can I put a 4.375" stroke crank in a 400 block? No. A 400 is a low-deck B block at 9.980" deck height; the RB stroker cranks and compression heights in this guide are for 10.725" RB blocks only. B blocks have their own stroker path with their own crank and piston part numbers.

Do I have to bore .060" over to build a 512? No — .060" over is just the bore that makes a 4.250" crank measure 512 ci. At .030" over the same crank builds 505 ci and behaves virtually identically. Build to what the block will safely take and call it what it is.

Will a 440 stroker fit with the stock oil pan? Usually, but verify it at mockup — the longer stroke swings the counterweights and rod bolts toward the pan rail and the pickup. Check counterweight-to-pickup clearance with the pan bolted down before final assembly, and plan on a windage tray for anything that revs.

Do stroker cranks need special bearings? They need bearings matched to the journal sizes the crank was actually cut to, which may be Mopar or big-block Chevy on the rod end. Measure the crank, then order. Beyond that, a good tri-metal performance bearing is cheap insurance on any stroker.

How much power will a 512 make? Displacement sets the floor; heads, cam and induction set the ceiling. A well-assembled 512 with good aluminum heads, a matched hydraulic roller and a dual-plane intake lands in a broad street-torque band and makes very usable power everywhere — the exact numbers depend on your specific combination. Chasing a peak number with a big single-plane and a large cam generally makes a street car worse to drive.

Internally or externally balanced — which should I buy? Internally balanced, if you are buying new anyway, and then buy the neutral damper and flexplate to match. Externally balanced strokers exist and work, but internal balance is the cleaner setup and is what most current aftermarket cranks are built as.

Building a 440? Start with the rotating assemblies collection, then match pistons, bearings and cylinder heads to the bore your block actually measures — not to the number printed on the kit.