Introduction: Why the Mopar 408 Stroker Is a Top Performance Upgrade

For Mopar enthusiasts, few engine modifications deliver the same blend of power, reliability, and cost effectiveness as the 408 stroker kit. Designed to increase displacement from the original 360 cubic inches to 408 cubic inches, this combination transforms a small-block Chrysler engine into a torque monster capable of pushing over 450 horsepower and 500 lb-ft of torque on pump gas. Unlike forced induction, a stroker build retains the linear throttle response and engine bay simplicity that many builders prefer. The Mopar Performance 408 Stroker Kit remains one of the most popular aftermarket packages for LA, Magnum, and even some Gen III Hemi applications.

But understanding the real cost requires looking beyond the kit price tag. Machining, balancing, gaskets, oiling system upgrades, and labor can quickly add up. This guide provides a complete price breakdown, explains power gains with dyno-verified data, and offers practical advice for building your own 408 stroker without overspending. We’ll also explore supporting modifications that let your engine reach its full potential.

What Is a 408 Stroker? Displacement and Compatibility

A stroker kit increases engine displacement by using a longer stroke crankshaft, together with shorter compression-height pistons and usually longer connecting rods. The Mopar 408 stroker is based on the Chrysler 360 cubic inch small-block (5.9L). By installing a crank with a 4.00-inch stroke (versus the stock 3.58-inch) and pairing it with 6.123-inch rods or 6.200-inch rods and custom pistons, the displacement climbs to 408 cubes. The result is vastly increased torque at lower RPM, without sacrificing high-rpm horsepower if the cam and heads are matched correctly.

Engine Families for the 408 Stroker Kit

The kit is primarily designed for the Chrysler LA small-block (1964–1992) and Magnum (1992–2003) 360 engines. These share the same basic block architecture, though Magnum blocks have slightly different oiling passages and require specific head gaskets. Many builders also use the 408 kit with late-model Gen III Hemi engines, but that requires a different crankshaft and piston combination due to the 6.1L/6.4L bore spacing. For LA/Magnum builds, the 408 package is a direct fit with minor machining (line bore/hone, cylinder hone, decking).

When choosing a 408 kit, you must decide on rod length and piston style. Two common rod lengths are used: 6.123 inches (stock 360 length) and 6.200 inches (popular for reducing piston side loading and improving rod-to-stroke ratio). The longer rod requires pistons with a different compression height and usually a slight relief for valve clearance.

Components of the Mopar Performance 408 Stroker Kit: Detailed Breakdown

The Mopar Performance 408 Stroker Kit (often sold under part number P5249467 or as a custom package from suppliers like Summit Racing, Mancini Racing, or 440 Source) typically includes these components. Prices vary based on brand, material, and quality level.

  • Crankshaft (4.00” stroke): Usually forged 4340 steel, internally balanced. Stock replacement cast steel versions exist but are not recommended for high-horsepower builds. Price: $800–$1,200. Premium brands (Callies, Eagle, Scat) on the higher end.
  • Connecting rods: 6.123” or 6.200” forged I-beam or H-beam rods. H-beam rods are stronger and preferred above 500 HP. Price: $300–$500 for a set of eight.
  • Pistons: Forged aluminum (e.g., JE, Wiseco, Diamond) with a compression height matching the rod length. Usually dish or flat-top to achieve 9.5–10.5:1 compression. Price: $400–$600 for a set.
  • Piston rings: Often included with pistons or available separately. Moly or steel top rings. Expect $50–$100.
  • Main bearings and rod bearings: Clevite or King premium bearings. $60–$120 for the set.
  • Cam bearings: Usually around $30.
  • Gasket set: Full Fel-Pro or Cometic head gaskets, intake, oil pan, timing cover, etc. $100–$200.
  • Timing chain set: Double roller preferred. $50–$100.
  • Oil pump: Standard or high-volume. $50–$100. Often upgraded to a Melling high-volume unit.
  • Hardware: ARP main studs, head studs, rod bolts. $150–$300.

Many kits bundle these parts together. A complete rotating assembly (crank, rods, pistons, rings, bearings) costs around $1,500–$2,200. Add gaskets, timing set, oil pump, and hardware, and the total for the “kit” is $1,750–$2,700, as the original article states. However, quality brands and optional upgrades (like a billet crank or forged rods) push the price toward $3,500.

Price Breakdown and Real-World Costs

Let’s look at a realistic budget for a high-performance 408 stroker build. Beyond the kit itself, you need:

  • Machine work: Bore and hone cylinders ($200–$400), deck block ($150–$250), line bore and hone mains ($200–$350), balance rotating assembly ($200–$400). Total: $750–$1,400.
  • Short block assembly: You can assemble yourself (saves $500–$1,000) or pay a shop ($600–$1,200).
  • Heads: Rebuild existing heads or purchase aftermarket aluminum heads (Edelbrock, AFR, Trick Flow). Budget $600–$1,500 for a good set.
  • Camshaft and valvetrain: A hydraulic roller cam and lifters ($400–$700), pushrods, rocker arms. Add $200–$400.
  • Intake manifold and carburetor: Single-plane or dual-plane (Edelbrock Performer RPM, Mopar M1). $200–$500. Carb: $300–$700.
  • Exhaust headers: $300–$800.
  • Fuel system: Pump, regulator, lines (if upgrading from stock). $100–$300.
  • Ignition system: Distributor, coil, ignition box. $200–$500.
  • Oil pan: A deep sump pan for clearance (some aftermarket pans needed for stroker crank). $150–$350.
  • Labor (if paying a shop): $1,000–$2,500 for full engine build and installation.

Total estimated project cost (parts and machine work, assuming DIY assembly): $4,000–$6,500. A professional turnkey build can exceed $8,000. These figures are essential for anyone planning a 408 build in a classic Mopar like a Duster, Challenger, Road Runner, or truck.

Power Gains: What You Can Expect on the Dyno

The 408 stroker’s power output depends heavily on the cylinder heads, camshaft, compression ratio, and intake/exhaust system. With a mild street cam and 9.5:1 compression on regular 93 octane, a typical 408 produces:

  • Horsepower: 400–450 hp at 5,500–6,000 rpm
  • Torque: 450–520 lb-ft at 3,500–4,500 rpm

Upgrade to a larger roller cam, aluminum heads with 190cc–210cc intake runners, and a high-flow intake, and you can see 475–525 hp with over 550 lb-ft of torque. Compare that to a stock 360 (about 250 hp and 360 lb-ft) and the gain is dramatic. Many builders report that the 408 pulls hard from idle to redline, making it a fantastic street/strip engine.

Forced induction builds (supercharger or turbo) on a 408 short block can push power well beyond 700 hp, but the cost and supporting modifications escalate significantly.

Installation Considerations and Critical Machining Steps

Building a reliable 408 stroker requires careful attention to a few critical details:

  • Block preparation: The 360 block must be magnafluxed for cracks, bored 0.030” or 0.040” over (depending on piston choice), and honed with a torque plate. The main bearing bores must be aligned and sized for the new crank. If the block is a Magnum, the oil passage for the lifters may need modification if using a flat-tappet cam.
  • Rotating assembly balancing: The 4.00” stroke crank is externally balanced for the 360’s harmonic damper and flexplate/flywheel? Actually, most 360s are externally balanced (weight on the balancer and flexplate). The 408 kit usually comes internally balanced. Double-check: many aftermarket kits use an internally balanced crank, requiring a neutral balance damper and flexplate. This is a common mistake—buying the wrong balancer can cause vibrations. Verify the balance specification before assembly.
  • Piston-to-valve clearance: With a 6.200” rod and high-lift cam, valve reliefs must be deep enough. Check with clay before final assembly.
  • Oil pan clearance: The longer stroke and larger rod journals may require a deeper oil pan or a kick-out pan to clear the rod bolts. Most aftermarket performance pans (Milodon, Moroso) work.
  • Head gasket selection: For aluminum heads, use composition gaskets with a 4.100” bore (Fel-Pro 1008 or Cometic).

If assembling yourself, invest in a quality shop manual, a torque wrench calibrated to the correct range, and a set of micrometers and bore gauges. Many builders have saved money by doing the work at home, but mistakes can be costly.

Supporting Modifications to Maximize Your 408 Stroker

A 408 short block is only as good as the parts that surround it. To fully exploit the extra displacement, consider these upgrades:

  • Cylinder heads: Stock iron 360 heads (302 casting) are the bottleneck. Aftermarket aluminum heads like Edelbrock RPM, Trick Flow 190/210, or ProMaxx flow significantly better. Expect a 40–80 hp gain over factory castings.
  • Camshaft: A hydraulic roller with around 230–240 degrees duration at 0.050” and 0.500”–0.550” lift is street-friendly. Solid roller cams (more aggressive) produce peak power above 6,500 rpm but require more maintenance.
  • Intake manifold: Dual-plane intakes (Edelbrock Performer RPM or Mopar M1 340) provide good low-end torque; single-plane (Victor Jr.) top out at higher rpm. For a street car, dual-plane is usually best.
  • Carburetor or EFI: A 750 cfm or 850 cfm four-barrel (Holley or Edelbrock) is typical. Modern throttle-body EFI systems (Fitech, Holley Sniper) offer easier cold starts and tuning adaptability.
  • Exhaust system: Long-tube headers (1 5/8” or 1 3/4” primaries) with a 3” exhaust (mandrel-bent) minimize backpressure.
  • Fuel system: A mechanical fuel pump may suffice for 450 hp, but electric fuel pump (rated at 80–100 gph) with regulator is safer for consistent fuel delivery.
  • Ignition: MSD distributor and 6AL box (or similar) for accurate timing and rev limit.

Without these supporting mods, a 408 long block may feel sluggish. Budget at least $1,500–$2,500 for intake, carb, cam, heads, and exhaust on top of the short block costs.

Cost-Saving Tips for Your Mopar 408 Build

You don’t need to spend a fortune to get impressive 408 power. Here are proven ways to reduce costs:

  • Buy a complete rotating assembly kit: Packages from 440 Source or Mancini Racing often include crank, rods, pistons, rings, bearings, and sometimes gaskets for under $1,800. This saves you time and typically costs 10–20% less than buying individually.
  • Use a stock block: The standard 360 block is strong enough for 500 hp. No need for an aftermarket block unless aiming for 700+ hp.
  • Reuse your stock accessories: Your current timing cover, oil pan, water pump, and front accessories often bolt on. Check clearance but many parts transfer.
  • Assemble the short block yourself: With patience and proper tools (ring compressor, torque wrench, piston ring filer), you can save $500–$1,000.
  • Look for used parts: Forums like For A Bodies Only, Moparts, and Dodge Dart sites have many builders selling leftover camshafts, lightly used heads, or even complete engines. Just be cautious with piston/cylinder wear.
  • Consider a stroker kit with a cast crank: If you stay below 450 hp, a cast steel crank (China-made) can save $200–$300. However, forged is safer for long-term reliability.
  • Do a stock head rebuild with a performance valve job: Instead of buying $1,200 aluminum heads, you can port stock 360 heads yourself (or have a shop do basic pocket port) and use a good spring/retainer kit. This can cut head costs by half.

Real-World Examples and Owner Feedback

On Mopar forums, the 408 stroker has a reputation for being a “sleeper” build: a stock-looking engine that surprises drivers of modern muscle. One owner on For A Bodies Only reported his 1973 Dodge Dart with a 408, Edelbrock RPM heads, and a 230/236 roller cam made 465 hp at 5,800 rpm and 510 lb-ft at 4,200 rpm. He spent $5,500 total (DIY assembly). Another builder in a 1972 Challenger used a Scat rotating assembly, AFR 210 heads, and a solid flat-tappet cam, hitting 501 hp and 542 lb-ft at the wheels through a manual transmission. His build cost $7,200 including machine work.

These real-world numbers confirm that the 408 is not only powerful but also tractable for street driving. Many owners note that the engine loves to rev, yet pulls smoothly from 2,000 rpm, making it ideal for daily driving or weekend cruising.

Comparing the 408 to Other Mopar Stroker Options

If you are budget-conscious, you might consider a 390 stroker (based on 340) or a 416 stroker (based on 360 with 4.10” bore). The 408 is the sweet spot: it offers about 70% of the power gain of a 416 but costs roughly 60% as much, because the block needs only a standard 0.030” overbore and the stroke is achievable with off-the-shelf rods. A 416 often requires boring to 4.060” (thin cylinder walls) or aftermarket heads with large bores, increasing cost. For most street-driven Mopars, the 408 is the most cost-effective stroker.

Conclusion: Is the Mopar 408 Stroker Kit Worth the Cost?

The Mopar Performance 408 Stroker Kit delivers exceptional value per dollar of horsepower. With a comprehensive kit ranging from $1,750 to $2,700 and a complete build cost of $4,000–$6,500, you end up with an engine that outperforms most crate motors in the same price bracket. Reliability is excellent when built with forged internals and proper machining. The key is to plan your build carefully, invest in the right supporting parts, and budget for machine work. For Mopar enthusiasts seeking a fun, torquey, and reliable engine, the 408 stroker remains a time-tested choice.

For more detailed specifications and purchasing, check out Mopar’s official performance parts website, or browse complete kits at Summit Racing. You can also find community builds and expert advice on For A Bodies Only and Moparts. With the right preparation, your 408-powered Mopar will deliver the kind of performance that turns heads and wins races.