Why is a wide seat used on exhaust valves?
Since exhaust valves operate at extreme temperatures, they require a wider seat to conduct heat away from the valve through the seat. Most shops specify 0.060- to 0.080-inch seat width for the exhaust side.
What happens if a valve seat is too wide?
And if the seat is too wide, there may not be enough pressure to provide a tight seal. A wide seat also tends to trap deposits that can hold the valve off its seat. This too, can reduce heat transfer as well as compression.
How do you measure valve seat contact width?
Measure the seat width with vernier calipers. It should measure approximately 1.1 mm (0.0433 in). Also, the seat should be uniform in contact area. If valve seat width varies, or if pits still exist, further cutting will be necessary.
What are the two types of valve seats?
There are two basic stem seal designs – deflector and positive seals.
What would happen if the valve clearance was too small?
If there’s too little valve clearance, the valves won’t fully close, causing excessive heat, and the engine will lose power.
How are valve seat inserts held in place?
When the valve seat insert and the cylinder head are at room temperature the seat is held in place tightly by the compressive stress in the cylinder head, Figure 3a. As the valve seat insert and the cylinder head heat up during the running of the engine a situation develops as in Figure 3b.
What is the function of the valve margin?
The margin for an exhaust valve should be larger to improve heat dissipation—generally around 0.080-0.100 inch. Because the flow path for an exhaust valve is the opposite of an intake valve’s, you will sometimes see a smooth radius on the chamber side to improve airflow into the port.
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.
How wide should a valve seat be?
There is some consensus on the width of the valve seat for the majority of applications. The intake side is generally around.040- to.050-inch wide with higher heat applications stretching to.060-inch. Of course, Pro Stock pushes the envelope all the time and runs in the.025- to.030-inch range.
What type of valve seat should I use for my engine?
When using titanium valves with steep angles, some type of copper alloy valve seat is preferred. Beryllium copper is popular, but some engine builders avoid it on the exhaust side due to beryllium’s carcinogenic warnings.
How wide is a 45 degree intake valve seat?
The 2.200-inch intake valve on the right has a .050-inch width for the 45-degree seat. There’s also a 33-degree backcut that measures .080-inch and a .080-inch margin. When using titanium valves with steep angles, some type of copper alloy valve seat is preferred.
What is the function of valves and seats in an engine?
The valves and seats in an internal combustion engine play a central role in engine breathing, compression, performance and longevity.