Probably... not much else it could be. Still, if it's really "1/4 quart" that's 8 ounces, a full cup. You must have used a lot of assembly lube

funny had a 467 SBC with ..oil pressure problems. Pulled pan to check bearings pan and pickup had sludge. Cleaned out replaced pump used AMSOIL problem solved. The motor is 15-1 and the guy uses Q16. i have seen this fuel and alcohol cause engine oil to break down and sludge. Avgas i believe could be a problem also. That motor runs 8.80s in 3200lb nova. Freshened after 150 passes and the motor was clean. Some race oils can be a problem also. The first oil in that motor was Brad Penn