Mopar Magnum Pushrods Replacement: Tools, Torque and Sequence
TL;DR: Replacing pushrods on a 3.9, 5.2 or 5.9 Magnum is a valve-cover-off job on a pushrod, overhead-valve engine with shaft-mounted rocker arms and hydraulic roller lifters. The work that decides whether the repair holds is not the pushrods themselves - it is finding out why the old ones failed, keeping everything in cylinder order, and loosening and retightening the rocker shaft assembly gradually from the centre outward rather than one bolt at a time. The valvetrain is non-adjustable, so pushrod length is a specification, not a preference. Torque every fastener in the factory sequence to the value in the service manual, and confirm the current part number for your engine against the manufacturer catalogue before ordering.
What you are actually working on
The Magnum family - Chrysler's 1990s revision of the LA small block, sold as the 3.9 V6 and the 5.2 and 5.9 V8s in Ram trucks, Dakotas, Durangos and Jeep Grand Cherokees - is a conventional pushrod engine. The camshaft sits in the block, hydraulic roller lifters ride the lobes, and each lifter pushes a pushrod up to a rocker arm that pivots on a shaft bolted across the top of the cylinder head. There is no adjuster screw. Preload on the hydraulic lifter is set by the geometry of the parts, which is why a pushrod that is bent, worn short at the tips, or simply the wrong length changes how the engine runs.
Two details separate this engine from a generic small block, and both matter for this job.
The rockers are on shafts, not on individual studs. You do not remove one rocker to free one pushrod. The shaft assembly for that bank comes off as a unit, and it has to come off evenly. Valve spring pressure is trying to lift it the whole time, so a shaft that is loosened at one end while the other end is still tight is being bent.
The pushrods carry oil. These pushrods are hollow, and oil that reaches the rocker gear travels up through the valvetrain to get there. A pushrod with a plugged or partly restricted passage starves the parts above it, and the wear you find at the rocker tip or the pushrod ball is the symptom rather than the cause. Verify the oiling path for your specific engine in the service manual before you assume anything, and hold every pushrod up to a light to confirm both ends are open.
Browse what is on the shelf under pushrods, or start from the engine family and work down through Mopar LA and Magnum small block parts.
Why Magnum pushrods fail
Pushrods are rarely the first thing to go wrong. They are usually the thing that records what went wrong.
| What you find | What it usually means | What else to inspect |
|---|---|---|
| A single bent pushrod | The valve stopped moving freely - a stuck valve, a broken spring, or an over-rev | Valve guide and stem, valve spring, retainer and keepers |
| Several bent pushrods on one bank | The rocker shaft was disturbed, or something was binding at assembly | Rocker shaft and shaft bolts, valve stem heights |
| Galled or flattened ball ends | Oil is not reaching that joint | Pushrod oil passages, lifter, rocker arm cup |
| A cupped or mushroomed lifter-end tip | Trouble underneath, in the lifter | The lifter itself, and the cam lobe under it |
| A pushrod that spins freely but the engine still ticks | The pushrod is fine and the noise is elsewhere | Lifter bleed-down, rocker shaft wear, exhaust leak |
| Blue or straw discolouration at one end | Heat from a dry joint | Oil supply to that cylinder, and the condition of the oil overall |
If more than one pushrod on a bank is damaged, treat that bank as a set. Mixing one new pushrod in with worn ones on a non-adjustable valvetrain gives you inconsistent preload across the head. Rocker gear and lifters are worth pricing at the same time - see rocker arms and trunnions and lifters.
Tools for the job
Nothing here is exotic, but three items are the difference between a clean job and a repeat visit.
A torque wrench that covers the low range. Rocker shaft and valve cover fasteners are small, and their values live at the bottom of a general-purpose click wrench where it is least accurate. A second, smaller wrench pays for itself the first time you use it.
A flat reference surface. A machinist's plate, a jointed straightedge or a pair of V-blocks lets you roll each pushrod and see runout instead of guessing. A pushrod can be bent enough to matter and still look straight in your hand.
An adjustable checking pushrod and a dial indicator, if anything has changed. If the heads have been surfaced, the block decked, or a different camshaft fitted, stock-length pushrods are no longer guaranteed to give correct lifter preload. That is measured, not assumed.
Everything else is ordinary: a socket set, a magnetic pickup tool, a gasket scraper and a non-chlorinated solvent, assembly lube, shop towels, and a set of valve cover gaskets. Hand tools and shop equipment are under engine stands and tools; sealing parts are under gaskets and seals.
Sequence: how the job actually goes
Work on a cold engine. A hot head, hot fasteners and hot oil make every step of this worse.
1. Disconnect the battery and clear the access. On these engines the intake ducting, wiring routed across the covers and various brackets come off before the valve covers do. Photograph the connectors and hose routing as you go, and label anything you would otherwise have to guess about later.
2. Remove the valve covers, but clean before you open anything. Any dirt sitting on the cover flange ends up in the valley the moment the cover lifts. Blow the perimeter clean first.
3. Rotate the crankshaft by hand and watch the valvetrain. Before you take anything apart, turn the engine over with a socket on the crank and watch each rocker open and close. A valve that hangs, a rocker that does not move with its neighbours, or a spring visibly shorter than the rest tells you the real fault while everything is still assembled and easy to interpret.
4. Loosen the rocker shaft assembly in stages, centre outward. This is the step people get wrong. Back the shaft bolts off a little at a time in several passes, working from the middle of the shaft toward each end, so the shaft rises level against spring pressure. Once the fasteners are free, lift the assembly off as a unit and set it down the same way up it came off.
5. Remove the pushrods and keep them in order. A piece of cardboard with numbered holes is the standard answer and it is still the right one. Note which end was up. Pushrods wear a directional pattern, and any old one that goes back in goes back the way it came out.
6. Inspect before you fit anything. Roll each old pushrod on your flat surface. Look at both ends under good light. Check that the oil passages are clear. Then look at what the pushrod was touching - the rocker cup, the rocker tip, the lifter seat. If a lifter feels notchy, spongy, or loose in its bore, deal with it now while the top end is open. Valvetrain parts are grouped under valves and valvetrain.
7. Fit the new pushrods with assembly lube on both ends. Seat each one properly in its lifter. It is easy to leave one sitting beside the lifter seat rather than in it, and you will not find out until the shaft is tightened and something is badly bent.
8. Reinstall the rocker shaft assembly and tighten it in stages, centre outward. The reverse of removal: several passes, working out from the middle, letting the hydraulic lifters bleed down as the shaft comes home. Do not run one bolt to final torque while the others are loose. Confirm every pushrod is seated in its rocker cup as the shaft comes down - stop and look before the last pass, not after.
9. Torque in the factory sequence to the value in the service manual. Rocker shaft bolts, valve cover fasteners and anything you disturbed on the way in all have specified values, and some carry a specified thread treatment or a one-time-use rule. Use the manual for your engine and model year rather than a number from a forum.
10. Turn the engine over by hand, twice. Two full crankshaft revolutions with no binding and no hard spot, before the starter ever turns. If something is wrong, this is where you find it for free.
11. Reassemble, start, and expect noise briefly. Hydraulic lifters that have bled down take a short while to pump back up. Persistent ticking after the engine is warm and oil pressure is normal is a reason to go back in, not a reason to drive it.
Frequently Asked Questions
Can I replace just one pushrod on a Magnum? Mechanically yes, and on a low-mileage engine with a single clearly identified cause it is reasonable. But if the bank shows general wear, or you cannot explain why the one failed, replace the bank as a set so preload is consistent across a valvetrain that has no adjuster.
Do I need to set valve lash on a Magnum? No. The valvetrain is non-adjustable and preload is set by component geometry, which is exactly why correct pushrod length matters. If the heads or block have been machined, or the camshaft changed, measure the required length with an adjustable checking pushrod rather than assuming the stock part still fits.
How do I tell a bent pushrod from a collapsed lifter? Roll the pushrod on a flat surface - that answers the pushrod question definitively. If it is straight and the noise persists, the lifter, the rocker or the cam lobe underneath it is the next place to look.
Should I replace the lifters at the same time? If any lifter is noisy, notchy by hand, or loose in its bore, yes. A pushrod that failed from oil starvation very often has a lifter behind it that is part of the story. If the lifters check out and the oil history is good, they can stay.
Are longer aftermarket pushrods an upgrade? Length is a fitment specification, not a performance choice. A longer pushrod on an otherwise stock engine increases lifter preload and can hold a valve off its seat. Length changes belong only where a measurement says they do. Wall thickness and material, on the other hand, are a legitimate upgrade for a high-spring-pressure build.
What else should I look at while the valve covers are off? Rocker shaft and shaft bore wear, valve stem tip condition, spring squareness and installed height, the oil drain-back passages in the head, and the general condition of the oil. Looking costs nothing extra - the covers are the labour.
Does the rocker shaft really have to come off evenly? Yes. The shaft is loaded by valve springs along its whole length. Loosening or tightening from one end puts a bending load into the shaft and an uneven load into the head. Several passes from the centre outward take an extra minute and prevent a bent shaft.
How long does this job take? Most shops quote it in hours rather than a day for one bank on an accessible truck installation, with more time for both banks, tight engine bays, or corroded fasteners. Getting the intake and wiring out of the way is usually a bigger share of the labour than the valvetrain work itself.
Sources
Written from the Core Powertrain Parts technical team's shop experience with Chrysler LA and Magnum small block engines, general engineering practice for shaft-mounted rocker gear and hydraulic roller valvetrains, and the internal Core Powertrain Parts collection and handle map used for the product links above. No torque values, pushrod lengths or part numbers are quoted here by design - confirm all of those against the factory service manual for your specific engine and model year, and against the parts manufacturer's own application catalogue.
Questions on a specific Magnum combination? Email sales@coretransmissionparts.com. Orders over $70 ship free.