All Pontiac oil pumps today are rated at the same volume and all use a 3/4" pick up tube. A high pressure Pontiac oil pump is available that is equipped with a longer pressure relief spring that is housed in an extended relief spring retainer. It was originally introduced by pontiac in 1973 for the 1973-74 455 Pontiac Super Duty engines.
The regulator spring on the 455 SD oil pump opens the by-pass at 60-70 PSI at 4,000 RPM. The two oil pumps are:
Melling M-54-F, with 60-70 PSI spring (must buy the 3/4" pick up screen separately).
Melling M-54D-S, with 40-50 PSI spring (includes 3/4" pick up screen).
Pressure rating is with standard bearing clearances. Maximum of .0015" rods and .0025" mains.
If you use the Melling M-54-F high pressure pump, you may have excessive distributor gear wear but the wear would not be evident in less than 20,000 miles. Pontiac introduced a special coated distributor gear for the 1968 -1970 Ram Air 3 and Ram Air 4 engines and indtroduced the 3/4" pick up screen. Prior to tghe 1968 Ram Air engines , all Pontiac oil pumps had a 5/8" pick up screen. . That special plated distributor gear was only installed on the assembly line and was never made available over the counter or as a service replacement. The special coated gear never had a part number. I installed a slightly used Ram Air 4 distributor in my 1969 Firebird 400 and the gear appeared to be cadmium plated.
Pontiac provided a special oil gallery NPT plug for the 1973-1974 455 SD engines that had a .030" hole drilled in the center of it for distributor gear oiling with the high pressure 455 SD oil pump. The 1973-74 455 SD engines used the M-54-F oil pumps for additional oil pressure for the large main bearings up to 6,000 RPM. The 455 SD engine blocks were designed for dry-sump oiling for 7,000 - 8,000 RPM. That oil gallery plug was discontinued by Pontiac in 1980. I purchased five of those plugs in the 1970s and used every one of them with the Melling M-54-F oil pumps. I tried to drill a hole in a regular "square drive" NPT hardened iron plug and it burned up all the .030" drill bits.
If you want to use a Melling M-54-F high pressure oil pump that is rated at 60-70 PSI at 4,000 RPM, , you will need to drill a .030" hole in the passenger side rear oil gallery plug using a EDM. Without a lube hole in that plug, the distributor gear will wear faster because of marginal lubrication. However, after 20,000 miles, that little .030" oil hole would probably be filled with sludge no matter how often you change your oil. The solution to the gear wear problem is to use the stock Melling M-54D-S oil pump that is rated at 40-50 PSI at 4,000 RPM.
Last edited by MouseFink; 10-14-2013 at 01:33 PM.