What is valve seat recession?
Valve recession occurs when wear of the valve or seat inserts in an automotive engine has caused the valve to sink or recede into the seat insert (as shown in Figure 1). Excessive recession leads to valves not seating correctly and cylinder pressure loss.
How do you prevent valve seats in a recession?
a) Adjust (retard) ignition timing to permit use of standard unleaded (95-octane) fuel.
- Use super-unleaded (98-octane) fuel.
- Use a commercially available lead-replacement additive in unleaded petrol.
- Overheating.
What is valve recession on a cylinder head?
Valve Seat Recession is when the valves from an internal combustion engine embed themselves into the cylinder head. This is generally due to a lack of lubrication between the valve and the cylinder head.
Is there lead additive for gasoline?
Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb(C2H5)4. It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially.
What is Valve stem projection?
Valve stem projection indicates the amount of wear that has taken place between the valve faces and valve inserts. The initial valve stem projection should be measured after the first 1,000 hours on a new cylinder head – the normal “beat-in” period in which the valve becomes seated on the insert.
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 a good lead additive for gasoline?
Classic Valvemaster, formerly branded Castrol Valvemaster, is the most effective and cost-effective lead replacement additive available for the protection of early vehicles designed to run on leaded fuel.
Why is lead added to gasoline?
In the early 20th century, automotive manufacturers were searching for a chemical that would reduce engine knock. In 1921, automotive engineers working for General Motors discovered that tetraethyl lead (better known as lead) provided octane to gasoline, preventing engine knock.
What is a valve seat in an engine?
In simple terms, the Valve Seat is the seat for the air intake valve and air exhaust valve. It is the part that makes contact with the valve, and maintains the airtightness of the combustion chamber.
What is valve seat width?
The ideal seat width for automotive engines is 1/16˝ for intake valves and 3/32˝ for exhaust valves. Maintaining this width is important to ensure proper sealing and heat transfer.
What is valve seat material?
Virgin TFE (PTFE) Made from Virgin Teflon, this is the most common valve seating material; its chemical compatibility is excellent for almost all media. Temperature -50°F to 450°F.
What is tappet setting?
Tappet clearance is a space between the top of the valve stem and the rocker arm. > Its purpose is to allow for some mechanical expansion and lengthening of the valve stem and push rods as the engine warms up. This clearance is also called valve lash.
Does lead additive boost octane?
Incidentally, lead also is used to boost octane or anti-knock quality to gasoline. Powershield does not boost octane. So, if your old engine needs a high-octane fuel, you might consider using an unleaded premium gas with a lead substitute.
Should I add lead additive?
The bottom line? It’s up to you, but chances are good that you and your engine will get along just fine without any lead substitute, as long as you’re running the proper octane for your car.
Why is ethanol added to gasoline?
Ethanol has a higher octane number than gasoline, providing premium blending properties. Minimum octane number requirements for gasoline prevent engine knocking and ensure drivability. Lower-octane gasoline is blended with 10% ethanol to attain the standard 87 octane.