Lunati makes this conical valvespring that bolted right on the existing Jegs heads. The spring-pressure difference is an interesting issue. If you look at our accompanying spring chart, you’ll notice that the stock springs in the Jegs heads offer virtually the same open-load pressure but lower seat pressure. The typical onset of valve “float” is actually where the spring bounces off the seat at closing. This is where the conical spring offers 40 percent more load to keep the valve on the seat.