Description 20v 4age – Valve stem seal set A full new and genuine set of valve stem seals. These are fitted on to the end of the valve guides. Suits both Silvertop and Blacktop 20v 4age head variants. Includes: Intake x12 and Exhaust x8. Testing the condition of existing seals There is a tell-tale sign when one or more of these valve stem seals are worn out that is very easy to check while driving a vehicle. With the engine running and left in gear, let the vehicle roll down a reasonably steep hill without any throttle being applied, let the revs build up (not past a safe limit!) from the momentum of rolling down and then on reaching the bottom of the hill press the throttle once again to drive off normally. When the throttle is applied if there is a puff / cloud of smoke that out of the exhaust then at minimum one of your seals isn’t functioning correctly. The reason why this happens is because when the engine is revved without any load and the throttle(s) shut the engine produces a vacuum in it’s cylinders, this will make it more prone to sucking oil past the valve stem seals (from the head) and temporarily accumulating in the engines cylinder(s). Once the throttle is applied again the fresh air / fuel mix will ignite this accumulated oil and create the smoke.
