Holley is merging with a special-purpose acquisition company in a deal that would value the aftermarket-auto-systems seller at roughly $1.55 billion.Controlled by private-equity firm Sentinel Capital Partners, Holley is combining with the SPAC Empower Ltd. to go public. Sentinel will be the combined company’s biggest shareholder if the deal goes through. The roughly $1.55 billion valuation includes debts. Holley makes and sells parts-including fuel-injection systems, carburetors, engine products and exhaust systems-for high-performance cars. Based in Bowling Green, Ky., it markets to car and truck enthusiasts to personalize their vehicles with brands such as MSD, Flowmaster and Accel.Launched over 115 years ago, Holley had net sales in 2020 of about $580 million, up more than 25% from the year prior. It would be one of the few companies going public through a SPAC that has been around for decades and has existing sales. Many others pursuing SPAC mergers are tied to futuristic themes such as space travel and green energy.