In classes where the compression...
In classes where the compression is limited, as in the case of the Busch cars limited to 9:1 compression, an exhaust valve that can handle extreme heat is required. The Manley NexTek valve is the valve engine builders have been waiting for to handle these extreme-heat situations.
Of all the reasons for exhaust-valve failure, it is believed by many that extreme temperature is the greatest factor. For this reason, Manley has developed a special stainless-steel exhaust valve that runs about 200 degrees cooler than a similar-weight titanium exhaust valve. Manley calls this new valve the NexTek, and it has a design and properties that make it worthy of that name.
The Valve Design
The NexTek valve uses XH-428 stainless steel and a completely new manufacturing technique to create a valve with a hollow stem and head. The hollow sections of the valve are filled with sodium. The sodium provides an internal cooling mechanism for the valve, drawing heat away from the valve head. This design creates a valve that offers the strength of a stainless-steel valve, is almost as light as a titanium valve (within 10 percent), and offers increased durability and reliability.
The chrome stem and integral hard tip, hardened to Rockwell Rc 55, ensure the valve will withstand the rigors of racing, and the swirl-polished stem promotes flow through the port.
Through proprietary manufacturing...
Through proprietary manufacturing processes, the NexTek valve is made with a hollow stem and head from XH-428 stainless steel. The hollow sections are filled with sodium. The sodium helps draw the heat from the head of the valve into the stem, using the valve guide as well as the valve seat to transfer heat from the valve.
Properties to Survive
The NexTek valve runs cooler than a titanium exhaust valve at the critical valve head area, which is very important with the increasing trend in compression-limited race engines. Through testing, it has been determined that a peak performing 9:1 compression race engine hashigher exhaust-gas temperatures (EGT) than a 14:1 compression race engine. With this knowledge, race-engine builders know the exhaust valve needs to be able to withstand even more temperature abuse with low-compression race engines. Instead of abandoning the low-weight titanium exhaust valves and sacrificing rpm in favor of durability, engine builders can choose the NexTek valves and have the best of both worlds. Manley offers these valves for everything from a small-block Chevy or Ford head to the wildest Winston Cup heads (SB2 and Yates) you can imagine. If you have heat-killing exhaust temperatures in your engine, check out the NexTek valve-it could be the solution to high EGT valve failures.
Manley Performance Products
1960 Swarthmore Ave.
Lakewood, NJ 08701
The chart shows how much better...
The chart shows how much better the NexTek valve is at transferring heat from the valve stem to the guide than a titanium valve. Heat transference helps to equalize the valve temperature across the length of the valve, reducing the chance of a valve seat being damaged from extreme temperature.
The area where the valve head...
The area where the valve head becomes the valve stem is called the fillet. The operating temperature of this area is critical to whether the valve will survive in an extreme situation. The data shows how much better the NexTek valve is at handling the 1,450-degree F exhaust-gas temperature.
Through testing, Manley was...
Through testing, Manley was able to determine the exact temperature gradient a NexTek and a titanium exhaust valve experienced in an engine. Notice that the NexTek valve has a more even temperature gradient along its length than the titanium valve.