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Rocker Arm Components
Rocker arm components are the poly locks, adjusting nuts, stud girdles, stands, bolts and shims that keep your rockers and valve lash in place. The parts you need depend on whether your heads use stud-mount or shaft-mount rockers, plus your thread size and rpm range. This guide explains what each part does and how to match it to your engine, so you get the right fit the first time.
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What Rocker Arm Components Do
Rocker arm components secure each rocker to the cylinder head and hold the adjustment that sets valve lash or preload. As the cam lobe lifts the lifter, the pushrod drives one end of the rocker, and the rocker pivots to open the valve. Every part in that chain has to stay put under spring pressure, or lash drifts and the valvetrain gets noisy or loses lift.
On a stud-mount head, a nut or poly lock threads onto each rocker stud and sets the rocker's position. Shaft-mount systems bolt a rigid shaft to stands or pedestals instead, with shims and bolts setting height and alignment.
This category covers that mounting and adjustment hardware. You'll find the rockers themselves under Rocker Arms and matching lengths under Pushrods. Retainers, locks and springs are in Valve Spring Components.
Rocker Arm Poly Locks and Adjusting Nuts
Poly locks and adjusting nuts set valve lash on stud-mount rockers, and each one has to match your stud thread. A standard adjusting nut threads onto the stud and holds the rocker at the height you set. A poly lock adds a set screw that tightens against the top of the stud to lock that adjustment, which helps keep lash from creeping.
Common options on this page include:
- 3/8"-24 poly locks and adjusting nuts for SBC, including JEGS and COMP Cams High Energy versions
- 7/16"-20 poly locks, including sets made for full roller rockers
- 3/8" adjusting nuts from ARP sized for rockers with a .620" slot
- COMP Cams adjustable rocker kits and replacement adjusting screw and nut sets
Match nut size to stud size before you order. If you're unsure which nut style your rockers call for, check the rocker manufacturer's spec.
Rocker Arm Stud Girdles for High-RPM Stability
A stud girdle ties the rocker studs together so they can't flex on their own, which stabilizes the valvetrain and prevents deflection at high rpm. It's a common upgrade for engines with high spring pressure, aggressive cam profiles or sustained high-rpm use. A girdle bar runs across the top of each row, and special adjusting nuts pass through it.
Those girdle adjusting nuts secure the poly locks threaded onto the studs, so your lash setting stays locked while the bar holds everything in line. This page carries Jomar Pro-Model stud girdles for BBC 396-500+ and 429-460 big-block applications. You'll also find Jomar 7/16" girdle adjustment nuts and COMP Cams girdle adjustment nuts with snap rings.
7/16" poly locks are a common size for girdle setups, but verify the size for your exact girdle and studs. Also check valve cover clearance, since a girdle adds height above the rockers.
Shaft Rocker Hardware: Stands, Bolts and Shims
Shaft rocker hardware mounts the rocker shaft to the head and sets its height, so stands, bolts and shims must match your system. Stands or pedestals form the base, and hold-down bolts clamp the shaft in place. Shims fine-tune stand height to correct rocker geometry, while thrust shims control side clearance.
Hardware on this page includes:
- Stand bolts in 7/16"-14 and shaft bolts in 5/16"-18 from Jesel
- Jesel stand height checking gauges for geometry setup
- Shaft rocker shims in .025" and 7/16" mounting bolts from Crower
- Thrust shims in .047" sets of 34, lash adjuster screw kits and 5/16" stud pedestal mounts
- LS rocker stands for LS3, LS9 and L92 heads, plus LS1, LS2 and LS6 rocker bolts
On LS engines, rocker bolt torque and tightening order matter. Follow the steps in how to install LS rocker arms with the right torque specs and sequence before final assembly.
How to Choose Rocker Arm Components for Your Engine
Choose rocker arm components by matching your rocker mounting style, thread size and rpm range. Start with the rockers on your heads, since they decide whether you need nuts and poly locks or a shaft hardware package. Next, confirm your stud or bolt thread, because a 3/8"-24 nut won't fit a 7/16"-20 stud.
A mild street build may only need quality poly locks. A high-rpm race engine with heavy spring pressure may benefit from a stud girdle or a shaft-mount system. If you're changing rocker style or adding a girdle, check valve cover clearance too.
Once you've narrowed it down, compare thread sizes and set quantities in the listings below. Shop Camshafts & Valvetrain for the cams, lifters and related parts that complete your top end. If you're not sure about fitment, call JEGS tech before you order.
ADD A VEHICLE TO GUARANTEE PARTS FIT
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ADD A VEHICLE TO GUARANTEE PARTS FIT
See products that fit
CHEVROLET PERFORMANCE
12600936 Rocker Arm Stand for GM LS Engines w/LS3, LS9 or L92-Style Heads Only
Part Number: 809-12600936
Ships Today
Lowest price guarantee
CHEVROLET PERFORMANCE
12600936 Rocker Arm Stand for GM LS Engines w/LS3, LS9 or L92-Style Heads Only
Part Number: 809-12600936
Ships TodayLowest Price Guarantee
SPEEDMASTER
Polylock Rocker Arm Nut Set, 7/16-20 in. Thread Diameter, For Full Roller Rocker Arms
Part Number: 746-PCE255.1005
Ships TodayLowest price guarantee
SPEEDMASTER
Polylock Rocker Arm Nut Set, 7/16-20 in. Thread Diameter, For Full Roller Rocker Arms
Part Number: 746-PCE255.1005
Ships TodayLowest Price Guarantee
Frequently Asked Questions About Rocker Arm Components
Can I reuse poly locks?
Often you can, as long as the threads are clean and undamaged and the set screw still seats firmly. Inspect each one for galled threads or a rounded hex before you reinstall it. If you're unsure, verify reuse guidance with the manufacturer or replace them.
How do I set valve lash with poly locks?
Rotate the engine until the lifter for that valve sits on the base circle of the cam lobe. Turn the poly lock to set lash or preload, then hold it with a wrench while you snug the set screw with a hex key. Recheck the setting after tightening, since the adjustment can shift. Use your cam card for the exact lash or preload spec.
Do I need new rocker arm components when I upgrade rocker ratio?
Sometimes, so check fitment before you reuse hardware. A higher-ratio rocker increases valve lift, but it also puts the valve closer to the piston, so check piston-to-valve and pushrod clearance. Our guide to 1.5 vs. 1.6 rocker arm ratios explains the tradeoffs. If the new rockers use a different stud or slot size, you'll also need matching nuts or poly locks.
Do full roller rockers need taller valve covers?
They may, because full roller rockers are often bulkier than stock-style rockers. Adding a stud girdle raises the height further. Check clearance with the covers you plan to run, and verify with the rocker manufacturer's spec or JEGS tech.
How do I confirm thread size for my rocker studs?
Start with your cylinder head or stud manufacturer's spec, since many performance heads use 3/8"-24 or 7/16"-20 studs. You can also measure the stud diameter and check pitch with a thread gauge. Once you know the size, match your nut or poly lock to it, and contact JEGS tech if the numbers don't line up.