Triple springs for drag boats
Who could imagine using the same set of valve springs for more than two years in a nitrous-infused 565 cu in V8 engine that competes in the quarter-mile on water?
Wayne Gaskamp has been able to accomplish just that with his 1800-plus hp engine that propels Mike DeClark's F Bomb drag boat in two categories of National Jet Boat Association (NJBA) competition, the seven-second and unblown fuel jet classes.
The NexTek-polished Manley triple springs of lightweight tool steel have been through at least 12 races over the past two seasons and make 12-15 passes down the quarter-mile during each race meeting. There are many, many test sessions between events to hone the tune-up for both engine and boat.
"Every time I take the motor apart we look at the valve springs," says Gaskamp. "We check the springs for pressure and they've always been good, so what I do is change the keepers - they take the real beating - and the seals, lash the valves and put it all back together."
Installed pressure is 350 lb at 2.100 in and open pressure is 1010 lb at 1.200 in. Maximum lift is 0.900 in, with outside dimension of 1.677 in and inside dimension of 0.635 in. The polished spring is intended to reduce friction, improve fatigue life and minimise lobe loss. Apparently it's living up to its billing.
While Gaskamp runs his V8 engine at 7500 rpm (8000 at the hit, and a maximum of 7500 through the balance of the quarter-mile pass on the water) the spring is capable of handling 10,000 rpm, which would lessen its longevity proportionally. Installation in the drag boat gives the spring a softer usage, thereby prolonging life greatly for the spring. "They take the beating extremely well; they're really good."
Gaskamp says he hasn't lost any pressure in the past two years and believes polishing of the spring, rather than coating it, has a lot to do with the longevity, "Keeping the springs alive and not breaking the ends is the objective. On this engine I use this particular spring because we have a lot of lift. It has a lot to do with the camshaft, your set-up and your geometry. The geometry of these springs is right on for the rocker arms; it's just happy where it's at," says Gaskamp.
Even with all his success in the current configuration - boat driver DeClark set the performance record in the NJBA's unblown fuel jet class of 7.15 s Elapsed Time at 144.46 mph in Bakersfield, California, this past April - Gaskamp is looking ahead to possibly changing the spec on his valve springs. This would happen following the current six-race season, on hold now until September, where DeClark handily leads the unblown fuel jet category and lies second in the seven-second class for drag boat competition.
"We're looking at the newest double spring for possible use," says Gaskamp "The designated lightweight dual drag race spring's advantage is its lighter weight. It'll rpm (or rev up) easier because of the lighter weight and, of course, they're a bit smaller because they're a dual spring, but they have the same pressure as our current, triple spring. There are less harmonics involved, as well."
Fig. 1 - This triple-spring Manley valve spring has been in the 565 cu in V8 for two years (Photo: Wayne Gaskamp)
Written by Anne Proffit