V-Series Valve Seat Insert


Inserts that meet or exceed all OEM standards

SVT V Series Valve Seat Our V series is our medium grade valve seat insert product line. The material composition is standard stainless steel with chrome being the major component. It is mostly used with unleaded fuel for all automotive applications. The hardness falls in 40-44 Rockwell scale due to heat treating. V-series exceeds OEM naturally aspirated standards.

High performance engines deserve a set of high performance valves. Because we’re in the business of squeezing the most performance possible out of any engine combination, valves are very much an important aspect to focus upon.

When your engine is running, the valves become extremely hot. As the valve closes and makes contact with the valve seat for a split second, the valve seat must absorb and dissipate some of the heat away from the valve, into the aluminum of the head to the water jackets to cool. That is where our material's ability to dissipate heat much quicker comes into play.


Valve Seat Removal and Installation Process:


Valve Seat Removal

Step one in any valve seat or insert replacement is correctly removing the old insert without damaging the head. There are several popular methods used in removing seat inserts from aluminum heads. Preheating the entire head in a special oven is very helpful to loosen the valve seats just enough so they can easily be preyed out. However, using this method can be a fairly long and tedious wait for it to start actually loosening. A second popular method is ti simply cut the insert out with a grinder of smaller diameter then the insert itself. Tis works well on soft-metal valve seat inserts, but not on powder metals. When you grind deeper, you'll find that the insert actually starts spinning inside the head itself. Now it should be easily by extracted out. A third method is to use a die grinder to cut into and actually weaken the seat. However, many times is accidentally made all the way through into the counterbore. Sometimes, simply trying to pry out the valve seats may work as long as there is enough of a lip under the inside edge of the seat. However, this can easily damage the counterbore if dine incorrectly. To remove very stubborn valve seats, an arc welder can also be used to place a bead around the seat. As the new bead cools, it will then shrink and slowly loosen the seat. The last method consists of placing an old valve that is smaller than the seat in the head and weld the valve to the seat. The now-destroyed valve stem is ready to be used to push out seat.

Valve Seat Counterboring

Many experts recommend re-cutting the counterbores to accept new oversized seats. Some engine builders will install new standard-sized inserts in the existing counterbores. It works on some large cast iron cylinder heads with thick walls, but it’s risky on most automotive applications. The recommended approach is to re-machine the counterbores to accept oversized inserts. This allows you to control the interference fit between the seat and head so the seats don’t come loose. Recutting the counterbore also allows you to control runout in the counterbore and concentricity with the valve guide. The counterbores must be smooth, round, have flat bottoms and be centered to their valve guides for proper alignment and good heat transfer between the seat and head. The final dimensions of the counterbores must be within .0005˝ for the proper fit. If a counterbore is too rough, distorted or out of round, it won’t make good metal-to-metal contact with the seat. It can also distort the seat. This will reduce heat flow from the seat to the head and make the valve run hot. That you don’t want because it leads to valve burning and warranty problems down the road. If you’re replacing an integral seat in a cast iron head (and the cylinder head has enough thickness to accept a new seat), the counterbore should be cut to a diameter approximately .100˝ larger than the valve head diameter. The inside diameter of the replacement seat will typically be about .100˝ smaller than the valve head diameter and require a depth of about .188˝ to .250˝ depending on the application. Accurate cuts also require proper fixturing. Keep your tooling setup as "short and tight" as possible to assure maximum rigidity. The less deflection in the tooling, the more accurate the dimensions of the cut and the greater the concentricity of the counterbore.

Valve Interference and Installation

The recommended amount of interference between the valve seat insert and head may vary depending on the size of the insert, the type of insert (alloy or powder metal) and type of head (cast iron or aluminum). The best advice is to use the amount of interference recommended by the OEM engine manufacturer. Too much interference runs the risk of cracking the head while too little interference increases the risk of the seat coming loose or falling out. One of the leading causes of seats coming loose, however, is not the amount of interference between the seat and head but elevated operating temperatures. Anything that causes the exhaust valve to run hot may also cause the seat to loosen. Some seats may require anywhere from .002˝ to .010˝ of interference depending on the application and the smothness of the surface in the counterbore. When using aluminum heads, an interference fit of .005" to .007" is typical. When using cast iron heads, .003" to .005" is about average. Some also recommend an interference fit of .005" to .006" for everything, aluminum and cast iron. Once the counterbores are cut, the seat installation is a basically straightforward. A driver is then used to push the seat into position. Some seats have a bevel or radius on the outside lower edge to make installation easier. Make sure this side faces down when installing the seat.

Seat Finishing

After the seats have been installed, they can be finished as required. The guides must be reconditioned or replaced before doing this, however, because all seat work is done by centering off the guides. Seats should be as concentric as possible for a tight compression seal and proper valve cooling. The rounder the seat, the better. Seat runout should not exceed .001˝ per inch of seat diameter. Some shops aim for .0005˝ or less of runout. The best way to check concentricity is with a runout gauge. Pulling vacuum on the valve port with the valve in place is another method for checking the mating of the seat and valve. But the ability to hold vacuum is no guarantee of concentricity. Both methods should be used to check the quality of your work. Seat width is also important for good heat transfer, proper sealing and long valve life. If the seat is too narrow, wear resistance and heat transfer can suffer. 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. As a rule of thumb, the ideal seat width for intake valves is usually around 1/16˝. For exhaust valves, it’s 3/32˝ – or whatever the manufacturer specifies. The point at which the valve and seat mate is also important. If the area of contact is too high on the valve face, the valve may be sunken into the head. This increases installed height, upsets valve train geometry and restricts free breathing. If the area of contact is too low on the face (too far from the margin), the valve will ride too high on the seat. As the engine warms up and the valve expands, the contact point moves down the valve face away from the margin. The valve may lose partial contact with the seat causing it to lose compression.