What is valve float and how does it impact engines?

Valve float means the valve doesn’t fully close at the proper time, because the return mechanism (usually a coil spring) isn’t strong enough to close it. This usually happens at high RPM. It can damage an interference engine if the valves make contact with the top of the piston.Dec 30, 2015

Can valve float damage engine?

This reduces engine efficiency and performance. There is also a significant risk of severe engine damage due to valve spring damage, and/or pistons contacting the valves, and/or catastrophic lifter and cam lobe failure, especially with roller lifters.

What are symptoms of valve float?

How is it identified? Mild valve float can be felt as power falling off quickly at high rpm. Severe valve float will be heard as a sputtering sound at peak rpm.

What it means to float a valve?

📓 High School Level. noun. a valve admitting or discharging a liquid to or from a tank and regulated by a float on the surface of the liquid within the tank to maintain a nearly constant height of liquid.

Does valve float cause backfire?

No backfires, no popping thru the exhaust, just runs real crappy at high rpm.

How does a float valve work?

How float valves work. Our float valves are not controlled electronically, like solenoid valves, but solely by the buoyancy force. In practice, the valve opens as soon as the water level falls below a certain level and stops the inflow as soon as this level is reached again. The fill level is checked by a floating body …

Will weak valve springs symptoms?

Symptoms of Weak Valve Springs



Weak valve springs will typically cause misfiring and a loss of power as engine speed increases. The engine may start and idle fine, or run normally up to 3500 to 4000 RPM.

How do you reduce valve float in automation?

They will go with stiffer valve springs in order to reduce valve float, also they will go with lighter valves (you can accomplish this by going with more smaller valves however a lighter material or design is generally done).

What is a valve lash?

Valve lash is the available clearance (or gap) between the rocker arm and the tip of the valve stem when the lifter for that valve is sitting on the base circle of the cam lobe (when the valve is intended to be fully closed).

What is the engine valve train?

A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine.

What do heavier valve springs do?

Simple physics tells us that heavier objects require more force to accelerate, just like a heavier car requires more horsepower to accelerate. Adding larger valves means the valvespring must control additional weight, more than likely at higher engine speeds.

What can happen if valve spring tension is too low?

If the spring pressures are too low, a condition called “Valve Float” will occur.

What causes an engine valve to drop?

A valve’s drop out can be caused by a variety of factors. The engine can run too fast, backfire (more than usual), fail to react well to valve tightness (also less than usual), fail to use a strong enough valve or not handle gears properly.

What happens when engine valves fail?

Consequence: The valve fails to close properly, overheats and burns through in the seat area. Fatigue fractures in the area of the fillet may also occur as a result of the unilateral stress of the valve head.

How do you know if your valves are bad?

The symptoms of bad valves include:

  1. Cold Engine. A cold engine test will give you a good idea if your valve seal is faulty. …
  2. Off-Throttle Braking. Engine braking involves employing different means to slow down your car asides from the external braking. …
  3. Idling. …
  4. Excessive Oil Consumption. …
  5. Excessive Smoke. …
  6. Loss of Engine Power.


What happens if an engine drops a valve?

If your vehicle experiences a dropped valve, you’ll need to have the vehicle repaired as soon as possible. Driving a vehicle with a dropped valve even for a very short period of time can destroy the inside of a cylinder and do other damage to the cylinder head as well.

What does dropped valve mean?

a valve, as for a steam engine, that drops freely to close.

What causes a valve to drop in a diesel engine?

The exhaust valves of a diesel engine are exposed to thermal and mechanical over stress which can cause valve failures. The exhaust valves fail due to different failure modes.