Tools and Materials Needed

Before diving into the installation, ensuring you have the correct tools and components on hand will save time and frustration. The Mopar Performance 440 Magnum camshaft is a direct replacement for factory 440 engines but requires precise assembly. Gather the following:

  • Mopar Performance 440 Magnum Camshaft – confirm part number (P4529736 or equivalent) for your year Road Runner.
  • Complete gasket set – including timing cover, intake manifold, and valve cover gaskets.
  • Timing chain and gear set – a double-roller set is recommended for durability with high-lift cams.
  • Camshaft installation tool – a long bolt with a handle that threads into the cam nose to protect the bearings during installation. A 5/16″-18 by 6″ bolt can work in a pinch.
  • Torque wrench – a ½-inch drive click‑type torque wrench capable of 0–150 ft-lb.
  • Socket set – metric and SAE (1/4″ to 3/4″ drive) plus deep sockets for head bolts.
  • Timing light – inductive pickup type for verifying ignition timing after installation.
  • Camshaft lobe lubricant – high‑moly paste applied to cam lobes and lifter faces on initial startup.
  • Assembly lube – for distributor drive gear and timing chain.
  • Engine oil and filter – 10W‑30 or 10W‑40 with high zinc content (ZDDP) for flat‑tappet cams. Rotella T4 15W‑40 is a common choice.
  • Coolant – 50/50 mix of antifreeze and distilled water.
  • Rags and cleaning supplies – shop towels, brake cleaner, and a magnet to retrieve dropped hardware.
  • Distributor wrench – to remove and reinstall the distributor without forcing the housing.
  • Lifters (flat tappet or hydraulic) – always replace lifters with a new cam. Avoid mixing used lifters.
  • Piston‑stop tool and dial indicator – needed for degreeing the cam and checking piston‑to‑valve clearance.

Double‑check that your engine is a standard 440 RB (raised block) and that you have the correct timing set for a 440 with the stock cam sprocket offset. Mopar Performance official catalog provides spec sheets for each cam.

Preparation Steps

Begin with a cool engine on a level surface. Disconnect the negative battery cable and secure it away from the terminal. Remove the hood for easier access—four bolts and a helper make this simple. Drain the engine oil and coolant. Remove the air cleaner, carburetor (if still installed), and intake manifold. On a 1968‑1970 Road Runner with a 440, the intake is a heavy cast‑iron four‑barrel unit; use an engine hoist or a second person to lift it.

Label all vacuum lines and electrical connections. Remove the fan, fan clutch, and water pump to expose the timing cover. If your car has an automatic transmission, remove the transmission cooler lines from the radiator. Clean the front of the engine block with degreaser so no grit falls into the timing cover.

Important: If the engine is still in the car, support it with a floor jack under the oil pan with a block of wood. This prevents excessive flexing when removing the harmonic balancer bolt. For in‑chassis work, you may need to remove the radiator and fan shroud.

Removing the Old Camshaft

With the front of the engine exposed, remove the harmonic balancer bolt (use a heavy‑duty impact gun or a breaker bar with the piston stop tool). Pull the balancer with a harmonic balancer puller. Remove the timing cover bolts and carefully pry off the cover. Note the condition of the old timing chain—excessive slack indicates a worn engine.

Remove the camshaft gear bolt and slide off the timing chain and gears. The factory camshaft is held in by its bearing journals and the thrust plate. Remove the distributor (mark the rotor position and housing orientation) and the fuel pump eccentric if equipped. Unbolt the camshaft thrust plate (two bolts) and slide the old cam out through the front of the block. Use the installation tool to gently pull and guide the cam without scratching the bearings.

Inspect the old cam lobes for wear—flat lobes often signal insufficient break‑in or low zinc oil. Check the cam bearings for scoring; if they are damaged, the engine must be pulled and the bearings replaced. Clean the cam tunnel with a lint‑free cloth and brake cleaner. Moparts forums have many threads on inspecting used camshafts.

Installing the Mopar Performance 440 Magnum Cam

Apply a generous coat of quality cam lobe lubricant (Moly‑based) to all lobes and distributor drive gear, plus a thin film on each journal. Slide the new camshaft into the block slowly, rotating it as you push to align with the bearings. Install the thrust plate with new bolts torqued to 15 ft‑lb. Always use Loctite 242 on bolts that could back out.

Remove the cam gear from the new timing set. Place the timing set on the crankshaft sprocket and slide the timing chain over the crank gear. Rotate the crankshaft until the #1 piston is at top dead center (TDC) on the compression stroke. Install the camshaft gear so the two timing marks (crank and cam) are aligned according to the timing set instructions (typically dot‑to‑dot or dog‑bone pattern). Tighten the cam gear bolt to 45 ft‑lb with Loctite 242.

Rotate the engine by hand two full revolutions to verify alignment. Use a dial indicator and a solid lifter (or a checker) to measure lobe lift and open/close events. Many aftermarket cams are ground with 4° of advance; if you prefer installed straight up, you may need an offset key. A piston‑to‑valve clearance check is mandatory with a high‑lift cam like the 440 Magnum. With the head and gasket installed but no valve springs, or with checking springs, bring each piston to TDC and measure clearance using a dial indicator on the retainer. Minimum clearance is 0.080″ for intake, 0.100″ for exhaust.

Reassembling the Engine

Install a new timing cover gasket and the timing cover. Tighten bolts in a criss‑cross pattern to 30 ft‑lb. Reinstall the harmonic balancer with the correct washer and bolt; torque to 135 ft‑lb (check service manual for your specific balancer). Reinstall the water pump with a new gasket (torque to 30 ft‑lb).

Clean the intake manifold sealing surfaces thoroughly. Apply a thin bead of RTV silicone at the front and rear china walls as recommended for your engine. Place the new intake gaskets with rubber end seals. Lower the intake manifold straight down; do not slide it. Torque the intake bolts in three stages to the factory spec (typically 45 ft‑lb for an iron intake). Reattach all vacuum lines, the carburetor, and the air cleaner.

Refill the engine with high‑zinc oil (5 quarts initially, then check after startup). Add coolant, but leave the radiator cap off for bleeding. Install the distributor with the rotor pointing to the #1 plug wire position. Do not fully tighten the hold‑down clamp yet. Connect the battery and ensure the ignition system is functional.

Testing and Break‑In Procedure

Before starting, prime the oil system to prevent dry starts. Use a priming tool in the distributor hole with a drill motor until oil appears at all rocker arms. If you have hydraulic lifters, adjust them according to manufacturer specs (typically 1/2 to 3/4 turn past zero lash). For solid lifters, set lash cold at engine builder guidelines (often 0.022″ intake / 0.024″ exhaust).

Start the engine and immediately raise the RPM to 2000–2500 RPM. Do NOT let it idle during break‑in. Run at varying speeds between 2000 and 2500 for 20 minutes while monitoring oil pressure, coolant temperature, and listening for abnormal valve noise. This procedure ensures the cam lobes and lifters wear in correctly. After 20 minutes, lower to idle and check for oil leaks. Shut down and let the engine cool for 30 minutes.

Check valve lash again after cool-down. Often hydraulic lifters need a re‑adjustment. Use a timing light to set initial timing to 10° BTDC (or per cam card). Then confirm total timing: at 3000 RPM with vacuum advance disconnected, total should be 34–36° BTDC. Adjust the distributor and lock down the hold‑down clamp. For B Bodies Only forum has excellent stickies on timing curves for the 440 Magnum cam.

Performance Gains and Tuning

The Mopar Performance 440 Magnum cam (often referred to as the “Purple Shaft”) offers a lift of approximately 0.484″ intake / 0.484″ exhaust with a duration of 268°/268° (advertised). This profile moves the power band to 2500–5500 RPM, ideal for street/strip use. Expect a noticeable increase in mid‑range torque, but you will lose some low‑end idle vacuum. Upgrade your carburetor and intake to match: an Edelbrock Performer RPM or Holley Street Dominator may improve flow. The stock Road Runner exhaust manifolds will choke the cam; invest in headers and a 2.5″ or 3″ exhaust system.

Ignition timing may need a recurve. Use a distributor with an adjustable vacuum advance can and limit mechanical advance to 20° in the distributor (giving 36° total). For street driving, set initial at 12–14° BTDC if using a vacuum advance. Upgrade to a reliable electronic ignition system (Mopar electronic or MSD) to avoid points float at high RPM. The strong vacuum signal of this cam can cause a lean condition at idle; adjust your carburetor idle mixture screws and consider stepping up your idle jet one size.

Conclusion

Installing a Mopar Performance 440 Magnum cam on your Plymouth Road Runner is a rewarding upgrade that transforms the engine’s character. By following these detailed steps—proper tool selection, careful removal and installation, and a disciplined break‑in—you’ll achieve reliable high‑horsepower operation. The 440 Magnum cam has been a cornerstone of Mopar performance since the early 1970s, and with proper tuning it will bring your muscle car to life. Always consult your specific cam card and service manual for torque specs, and do not hesitate to reach out to the Mopar community if you hit a snag. Dodge Garage’s technical guide on cam break‑in is an excellent additional resource.