One issue did surface early in development. The Holley pump produced more fuel pressure than was needed. Typically 7 to 71/2 PSI being ideal, but above that, the carburetor metering system was disrupted. Holley resolved the issue with an external fuel-pressure regulator, adjustable to the exact pressure desired.
Prototype pumps were built and application issues explored. One field-testing session took place at Milan Dragway in Michigan with local racer Wally Booth. A successful Super Stock racer, Wally was already competing in Pro Stock with his 1968 Chevy Camaro with race partner and engine builder, Dick Arons. Wally had removed his twin Stewart-Warner pumps and installed one new Holley electric pump. He also installed the adjustable Holley pressure regulator and a fuel-pressure gauge, setting it to 7 PSI for the Holley R-4224, 660-cfm “center squirter” carburetors he was using.
Wally, Dick and crewmen Gordy Foust and Dave Tratechaud joined Holley project engineers one spring morning. After warming the big-block engine, Wally warmed the tires with a burnout, then staged. At 6,000 rpm, the Camaro picked up both front wheels in the air through first gear. The first run was a 10.08-second elapsed time at 132.44 mph. After chassis tuning and engine adjustments, two more runs were made, with a best 9.95 e.t. at 134.23 mph. While those numbers seem slow by today’s Pro Stock standards, they were at the top for the day. More importantly, the new Holley pump performed exactly as expected.
After production samples were made and quality control checks performed, production began at Holley’s Bowling Green, Kentucky, plant. Pumps were sent out for testing to top Pro Stock racers Bill Jenkins and Don Nicholson. Both reported excellent results running the new Holley pump and regulator in open competition and match races. Wally, Bill, and Don later appeared in Holley advertising endorsing their use of the new Holley pumps.
Bill installed a Holley GPH-110 pump and regulator on his new small-block Chevy-powered Vega, the car that turned Pro Stock racing upside-down in 1972. Bill and his Vega also appeared in a Holley ad, telling all why he believed in the Holley electric pump.
The Holley blue pump became the overwhelming favorite of not only Pro Stock racers, but also those embracing Pro Stock technology for Super Stock, Modified and Competition Eliminators, taking advantage of the deluge of technical advancements in carburetor and fuel-delivery technology at the time. Holley has continued to refine and re-engineer the GPH-110 pump as needed and add many new fuel-system products to its product line over the years.