The oil pumps, intermediate shafts, and pickup-screen assemblies that Melling produces were created from original GM drawings. “This allows our components to fit the exact application,” says Mike Osterhaus, product development manager at Melling. “By applying our knowledge of pump design to the internal features of the housing and components, we can improve performance and durability. We don’t consider a Melling oil pump good enough unless it exceeds the expectations and specifications of the original it replaces.”

Melling began manufacturing its M-54-series oil pumps for Pontiac V-8s in 1963. “The original No. M-54, which was our standard-volume pump, rated at approximately 40 psi, was discontinued around 1990,” says Osterhaus. “We presently manufacture and 100-percent test four specific oil pumps for Pontiac V-8s at our Michigan facility. That includes our OE-replacement Nos. M-54D and M-54F, and Nos. 10540 and 10541 in our Select Performance line.”

He continues: “The M-54D oil pump is designed as a replacement for any 265-455ci Pontiac engine and uses the larger ¾-inch-diameter inlet opening. Its pressure bypass is set at 50 psi. The M-54F is a replacement for certain Ram Air and Super-Duty 455 engines. It uses a specific bypass valve that’s designed to increase maximum oil pressure by roughly 20 psi when compared to the M-54D. The volumetric displacement of the gear set we use in either is roughly 2 ci per revolution.”

Osterhaus is quick to point out that even though the pressure bypass valves actuate at 50 and 70 psi, respectively, it doesn’t necessarily mean that oil pressure within the engine will be exactly 50 or 70 psi.

“It’s dependent upon such variables as engine speed, bearing clearances, and oil temperature and viscosity. Actual pressure could be higher or lower depending upon the particular engine and where the oil pressure reading is taken.” When dealing with a typical Pontiac V-8 and production-bearing clearances, pressure at the gauge is usually 60 and 80 psi, respectively.

Melling’s Select Performance oil pumps were first introduced in the early ’90s and incorporate improvements to the pump design, displacement, tolerances, materials, and coatings. “Our Nos. 10540 and 10541 fit the same respective applications and bypass pressure settings as our M-54D and M-54F units. The tolerances and clearances of the Select Performance units are improved to maximize performance and reliability in high-performance applications,” Osterhaus says.

Butler Performance Pro-Series

Butler Performance is intimately familiar with the Pontiac lubrication system. “The Pontiac oiling system is very good, and the basic Pontiac oil pump is a decent design,” says David Butler. “The original pumps were sufficient for the intended applications, and they’re quite reliable—many went 100,000 miles or more without incident in their original engines.”

If there is a weakness within the Pontiac oil pump, Butler believes it’s the ball-type bypass valve. “If some debris or a small metal sliver gets lodged between the check ball and its seat, the ball may stick open. That can cause oil pressure to fluctuate, also routing some oil flow back toward the inlet side of the pump. Whether or not that actually affects performance in a typical street engine is unclear. It can mean disaster for a high-performance engine, however.”

Butler Performance has used and sold Melling oil pumps for many years. “Just as Melling states, we’ve found that the fit and finish of its Select Performance pump is better than the M-54 series unit,” says Butler. “We recently begun offering our own Pro-Series oil pump. We picked up where Melling left off, modifying its basic pump to further improve performance and reliability for high-performance applications, and then we bench-tested it to ensure complete functionality.”

David Butler says the company developed its Pro-Series pump to eliminate any chance of an oil pump-related issue on new engines. “Because it’s been pressure-tested, we know that it will operate consistently and reliably; that reduces the number of variables that could cause an operating issue at initial engine startup. We consider our Pro-Series pump as cheap insurance to prevent low oil pressure on initial startup, and we use it in many of the engines we build.”