This is the check-valve/anti-drain back assembly in its proper assembly and position:
This is a commonly available, one-piece replacement, for the assembly. Be sure to install an o-ring on this replacement.
DO NOT use this style replacement with a stock oil filter package. The stock oil filter design does not have a bypass function and neither does this one-piece design. A clogged filter without a bypass available can literally explode!
This replacement needs to be installed with the ‘window’ toward the side of the block. As with the OEM style assembly, this replacement valve does restrict the flow of oil going to the oil filter, especially if the ‘window’ is not properly placed.
An option to the above ‘valves’ is a simple cup-type plug that is pressed into the drilled passage and lodges between the horizontal lines going to and from the oil filter. This plug is not to be used with the original style oil filter assembly.
The original valve assembly has two functions: pressure by-pass and anti-drain back. Not all EarlyHemi engines have both parts, and some, did not have any.
The pressure by-pass was required in the event that the filter plugged and would not pass oil. This was common in the days of non-detergent oil and lack of maintenance. Without the pressure by-pass valve the oil canister could explode if the oil pump did not fail first.
The anti-drain back portion of the valve was needed to insure that the filter did not self-empty and create a dry-start condition. Most of the factory filters were mounted up-side down.
The internal check-valve/anti-drain back assembly is required in some form, to direct oil flow to the filter. Without ‘something’ in the block, the oil will simply take the path of least resistance and go straight up into the block and miss the filter. The stock assembly can be used with all modern filters. Various styles of ‘plugs’ have been used to block the oil passage to force oil to the filter. In some of the EarlyHemi engines the block is not drilled through and resembles the late model 318-360 design. The oiling systems are very similar in this area.
If your valve assembly looks like the first photo, or only one-half of the first photo, then you have a common block and you can use a plug like the one in the second photo. Or, as depicted in the last image, you can use a very simple core-type plug. You can even make one if desired, however, the plug must not interfere with the horizontal passage to the filter.
Most modern spin-on filters have a pressure by-pass feature internally; if the filter media plugs up then oil flow is by-passed back to the block.
Here is a link to WIX filters, it is our preferred filter brand for all applications. The 51515 is used for most Mopar applications, but be sure to look around for the complete line of filters for your other vehicles and equipment.
Only some of the modern filters have what is considered to be an anti-drain back feature for filters mounted in some vertical fashion, with the mounting surface down. There is a ‘stand-pipe’ of sorts that allow the filter to be mounted up-side down.
If the filter is mounted in a mostly vertical position, with the mounting surface at the top, then modern filters will not self empty, even without the stock anti-drain back assembly.