Atomic Barra Street Chain Tensioner
Engineering Overview
SPEC-DOC
Atomic Barra Street Chain Tensioner
⚠️ CRITICAL WARNINGS
DO NOT ADD CLICKS TO THE RATCHET. DO NOT FORCE OUT THE PISTON OR LEVER THE GUIDE. INSTALL THE TENSIONER AND PULL THE 'GRENADE PIN' ONLY.
Modification of any part of the tensioner voids the warranty. Removal of the check valve system or any other component (other than the retention pin which is removed during install) will void warranty.
A Durable OEM+ Solution
The Atomic Barra Street Chain Tensioner is designed as a drop-in OEM+ replacement to offer a significantly more durable and refined solution for factory and performance street applications. Machined in Sydney from Billet Steel, it improves upon the factory design's kinematics, damping, and material strength all of which improve load bearing ability and therefore durability.
While we have heavily improved how the tensioner regulates chain tension and dampens harmonics, it is designed to operate optimally up to 80psi of oil pressure. You can run more oil pressure than that, but doing so will subject you to the same limitations as the factory tensioner: over-tensioning the chain. The more oil pressure you have, the more tension you put on the chain. Over-tensioning can cause the timing chain or chain guide to snap due to excessive force. The total load capacity of the timing system is reduced as you introduce more spring pressure, aggressive cam profiles, increase RPM and introduce other shocks like harsh limiters or poor harmonic damping.
At 80psi, we are confident this tensioner will not have the same reliability issues as factory units. Our comprehensive testing program included such tests as revving to 6000rpm and hold on a harsh rev limiter instantly from a dead cold start. We've tried. Multiple times.
Key Capabilities
- Application: Factory replacement, performance street builds.
- Oil Pressure Limits: Recommended Max 80psi.
- Deck Height Limits: Tolerates +/- 1mm deck height variations.
Engineering Enhancements
Material & Alignment
- Billet Construction: Billet steel body, piston, and EN steel ratchet for vastly improved tolerances, finish and strength.
- Revised Geometry: Improved kinematics and orientation for lower noise, vibration and harshness.
- Enlarged Piston: Increased size improves contact surface and tooth size, reducing tensioner tooth wear through better engagement.
Damping & Hydraulics
- ICV & TFD: Integrated Check Valve & Tuned Flow Damping circuits to enhance absorption of chain whip.
- Cold Start Flow: Improved air bleeding speeds up damping function, especially critical on cold starts.
- Main Spring: Increased stiffness aids cold starts on modified engines.
- Guaranteed ICV sealing: Every unit is machine tested before being packaged to guarantee perfect check valve function
Failsafes & Protection
- Single Tooth Ratchet: Significant improvement to ratchet tooth design using a single, deeper 90° engagement tooth. Not only does this increase the load-handling ability of the tensioner, but we have also slightly increased the tooth spacing/damping window. This reduces the harshness introduced when the ratchet lock takes the force, allowing hydraulic damping to properly dissipate the energy BEFORE it smashes into the locker.
- Reduced Tooth Count: Reduces 'over-ratchet' which over-extends the piston and forces the guide to absorb chain harmonics.
- Mechanical Backstop: The body acts as a backstop in the event of ratchet or oil supply loss.
- Over-extension Protection: Added to avoid piston pump-up and guide/chain snaps.
Atomic vs. Factory Tooth Design
Technical Specifications
| Component | Specification |
|---|---|
| Body | CNC Billet Steel |
| Piston | CNC Billet Steel |
| Ratchet | CNC Billet EN Steel |
| Damping Tech | ICV (Integrated Check Valve), TFD (Tuned Flow Damping) |
| Target Oil Pressure | Max 80psi |
| Recommended Guide | Atomic Billet Street Chain Guide |
🔧 Installation Advice
- Loctite all mounting bolts.
- Prime oil system by cranking prior to start to fill the head and tensioner with oil.
- Normal Operation: The tensioner may make a buzzing noise for several seconds after first start as air bleeds out of the system. This usually only repeats if the engine is not started for extended periods.
- DO NOT attempt to add more tension to the guide manually
- Rotate engine by hand before sealing up. Tensioner may extend one click so please note tensioner movement and resting position. We recommend taking a photo for future reference. This will also help with troubleshooting or warranty claims if difficulties arise.
🔍 Troubleshooting
- Cannot install (piston fully in): Deck height is likely out of the designed range. Contact Atomic with your head gasket and head/block specs.
- Loud rattle/tap after first start: If noise persists and worsens with RPM, you may have left the retention pin in behind the ratchet mechanism. The pin MUST be removed prior to startup.
- Persistent tapping/buzzing: If you have good oil feed and the pin is removed, you are likely experiencing normal NVH from the Barra timing system. The Street tensioner improves dynamics, but is limited by other factory chain paths. If the noise sounds abnormal or particularly harsh, it may be the guide hitting the tensioner body. Contact Atomic for advice.
