Pushrods and Valve Springs: The Critical Supporting Mods for Your HEMI Cam

Why Stock Valve Springs Fail With Aftermarket Cams

The factory HEMI valve springs are designed for the stock cam's lift and duration. They have a specific installed height, spring rate, and coil bind clearance calculated for stock specifications.

An aftermarket cam increases valve lift — sometimes dramatically. A Stage 2 cam might lift the valve 0.050" to 0.080" more than stock. If you run stock springs with this increased lift, two things happen:

1. Coil bind: At maximum lift, the spring coils may contact each other (coil bind), which can break the spring and send metal shards into the engine

1. Valve float: Even before coil bind, a spring that's too soft for the cam profile can't control the valve at high RPM. The valve "floats" — doesn't seat properly — causing power loss, misfires, and eventual valve/seat damage

How to Choose the Right Valve Springs

Your cam manufacturer specifies the required spring:

• Installed height: Distance from retainer to spring seat — must be correct for your specific cam
• Open pressure: Force at full lift — must be sufficient to control valve velocity
• Seat pressure: Force at closed valve position — must seal the valve reliably

Always use springs specified by your cam manufacturer. Mixing brands or using generic "upgrade springs" that aren't specced for your cam is risky.

Popular spring suppliers for HEMI cams:

• Comp Cams: Sell springs matched to their cam kits
• Melling Performance: Good quality, reasonable pricing
• Trick Flow: Quality components
• EPS (Engine Power Source): Popular HEMI cam and spring combinations

Pushrods: Why Length Matters

The Gen III HEMI uses a dry-sump-style valvetrain where pushrod length is critical for proper geometry. The pushrod sits between the lifter and the rocker arm — if it's the wrong length, the rocker arm doesn't contact the valve tip in the correct position, causing side loading, accelerated wear, and reduced lift.

Aftermarket cams change the effective pushrod length requirement because:

• Different base circle diameter than stock
• Different lifter travel
• Different rocker geometry when matched with upgraded springs

How to Determine Correct Pushrod Length

The definitive method: use a pushrod length checker tool (available from Comp Cams for ~$50). With the cylinder head installed and proper springs, you cycle through candidate pushrod lengths until the rocker arm geometry is correct at mid-lift.

Alternatively, your cam manufacturer's kit specifications include recommended pushrod length ranges — most Stage 1–3 HEMI cam kits include the correct pushrods.

Standard HEMI pushrod diameter: 3/8" — don't go smaller. Larger diameter pushrods are available for high-RPM builds.

The Master Kit: The Easy Path

The simplest way to get all supporting parts right: buy a complete cam master kit that includes:

• Camshaft
• Matched lifters (non-MDS)
• Valve springs (inner and outer)
• Retainers
• Keepers
• Pushrods (correct length)
• Installation guide

Kits from Comp Cams, Melling, and EPS eliminate the guesswork. Everything is spec'd to work together. Budget $600–$1,500 for a complete quality kit depending on cam profile.