OVERVIEW
The oiling system is comprised of several components; the oil pan, the pick-up tube and screen assembly, the oil pump, and the intermediate drive gear/shaft assembly.
The pickup tube and screen assembly was made in several configurations based on which pump was used with which oil pan. Some tubes screw into the pump housing and some have a ‘floating’ connection, not to be confused with a ‘swinging’ connection.
New, replacement assemblies are no longer available, however, many of the current assemblies in Mellings inventory can be used in whole, or in part, to rebuild or partially replace the original.
The original oil pumps came in several varieties. There are some rebuild ‘kits’ still on the market, however, a worn pump body may not see all of the benefits that the new internal parts could provide.
There are two different mounting patterns for all of the Hemi and Hemi-based Poly oil pumps. The 51-53 Chrysler 331 is distinct, all others use a slightly different pattern. Currently, the only pump being made is the Melling M50, as designated for the 57-58 392. This is essentially the same pump as was used in the Dodge engines prior to the development of the 392, but with one important difference. The original Dodge pump is 0.3125″ shorter than the 392 (M50) pump and this can cause problem when the M50 is used as a replacement in a mostly stock Dodge because the oil pan will likely hit the pump unless the pan is a rear sump style. See the pump photos in the following section on Oil Pumps.
The early DeSoto pump ‘looks’ alot like the 331 pump but has a different mounting pattern, ie, the 392 style. Additionally, the 54-55 331 pump also looks like the early pump but with the later pattern.
The M50 bolts directly to all engines except for the 331 mentioned, however, there are numerous different pickup tube designs that must then be accounted for. The M50 pump is considered to be a high volume design and is sufficient for all street driven vehicles and is used in many drag race engines without further modifications. Melling has conducted flow tests and the M50 flows approximately the same volume as the M72HV which was specifically designed as a high volume pump for the LA engine series.
The intermediate shaft and gear assembly is specific to the engine assembly generally based on high vs low deck. There are stock replacement assemblies available and also replacements for use with the shorter LA distributor in each engine series. Note: the 241-260-270 Dodge engines have the same block dimensions (in this regard) as the LA series and can utilize the LA distributor without further modifications. Although there are minor variations in overall length with the DeSoto, the Dodge 315-325 and the Chrysler 331-354, the same shaft can be used. The 392 has the longest of all shafts.
The drive gear for the Hemi engines is the same as all A and LA series engines, with one exception (56-58 A engine/smaller OD) so there is adequate availability when needed. Additionally, bronze replacement gears are also available if a billet steel camshaft is used.
Some of the drive gears are secured to the shaft with a pressed-in pin and others will be found with a interference press fit. Either style of attachment is acceptable.