Hollow drag
The use of hollow stem titanium intake valves is slowly beginning its reach into the drag racing community, as a few Top Fuel teams are taking on the use of these weight saving and power enhancing parts that are used in many other series. Sometimes it just takes the drag racers a bit longer to embrace newer technology, notes Tom Abbett, team manager and cylinder head specialist at Mike Ashley Racing.
According Abbett, this type of intake valve significantly lightens the overall valvetrain and is easier on the lifters, camshaft, rockers and valve springs during standout driver Antron Brown’s sub-four-second, 1000-foot trips down the dragstrip. In his second year competing in this category, at the time of writing Brown stood second in the NHRA Top Fuel Full Throttle Racing Series points chase and was a two-time 2009 winner.
When Mike Ashley Racing switched to Alan Johnson cylinder heads toward the end of the 2006 NHRA drag racing season, the transfer of seat material to the valve was a heat-related issue for Abbett. “We tried to lighten it up but there wasn’t a big difference. It was the CrN (chromium nitride) coating (provided by the Xceldyne division of CV Products in North Carolina),that reduced material transfer. Once we had that, we could control valve life, get the valve to last longer and the springs to last longer,” he said.
Through the use of this CrN coating on his Xceldyne hollow-stem titanium valves, Abbett has discovered the life cycle of his springs improved and he gets three times the life from his valves. “We get eight to 12 runs now where we were lucky to get two runs before. We used to go through a lot of intake valves… “ he mused.
The valve in a Top Fuel engine making nearly 8000 horsepower has a tendency to get burned before failure of a coating occurs but as Abbett explains, “That is another part of those tune-up issues we constantly face.”
Not every nitro-powered car in the NHRA uses either hollow-stem valves or CrN coatings. There is a $25 financial penalty for the coating, Abbett told me. Some of the Funny Car teams are reluctant to try hollow-stem titanium valves because those machines are more susceptible to fire when the intake valves fail. The backfire can go on to the blower (supercharger) and ignite ferociously from there, Abbett explained (Mike Ashley Racing competed solely in the Funny Car arena until this season).
Another good technology boost for the Top Fuel team is Xceldyne’s change from square to round keeper grooves for the intake valves. “There is less tendency to pop the head off with these round keeper grooves,” Abbett said. “It, too, has certainly helped with valve longevity.”
Written by Anne Proffit.