The new twin-Chrysler-powered Unlimited Hydroplane is out to revolutionize Gold Cup racing.
Reprinted from Hot Rod magazine, September 1970
With those big World War II Allison engines becoming scarcer than hen's teeth, Dave Heerensperger, Chairman of Pay 'n Pack Stores, decided to use a pair of Keith Black "elephants" to power his new unlimited hydroplane, "The Pride of Pay 'n Pack." Hull design is by the father and son team of Ted and Ron Jones of Costa Mesa and follows their new and revolutionary pickle-fork tunnel-hull configuration. The relatively new driver-ahead-of-engine design, known as cab-over, attains the desired effect of moving the center of gravity farther aft than in the conventional three-point hydro. Most three-pointers will average 150 to 160 in the chutes but slow to about 80 mph in the turns. The new low profile, combined with tunnel-hull lift, will produce about 150 in the chutes, and the relocated C/G will result in not under 110 in the corners. "Pay 'n Pack" is shorter (28'6" as opposed to most unlimiteds' 30-31'). It's also wider - 13', about a foot more than usual. Water pickup and pitot tube are in leading edge of rudder.
The unique tunnel hull is constructed of white oak, northern ash, mahogany and birch plywood, with the underside completely sheathed in aluminum. There is over two grand invested in aircraft stainless steel braid covered lines and fittings. The custom-made V-drive gearbox was built by Casale and has a ratio of 1.67:1. This super-light box has an integral oil pump for lubrication, plus a water-cooled jacket. The usual unlimited gearbox weighs about 300 to 400 pounds. Weight saving is a big factor in this boat's performance. The bare hull weighs only 1900 pounds; in racing trim she will weigh about 5000 pounds. Most unlimiteds weigh from 6500 to 8000 pounds. Special linear electric drive motors are used to actuate the engine couplers. The couplers can be operated from the cockpit, allowing on-the-beach runups without a spinning prop; or in case of engine failure, the boat can finish on one engine. Tommy "Tucker" Fults was the first driver but relinquished the helm to Ron Larsen when it seemed that some time-consuming debugging was going to have to be done.
A pair of these 473 Chrysler hemis on alky are rated at 1100 hp each. The GM blower utilizes a Cragar drive and manifold on the Chrysler block equipped with Forged true pistons and rings on Carrillo rods turning on a Moldex crank. Keith designed the cam and uses the new Spalding solid-state CD ignition. The Black dry-sump unit has two scavengers and delivers 105 psi at 185° through special oil coolers. With couplers at each end, engines are interchangeable and can be switched in 15 minutes. Fin holds boat in turns.
