R Model Air Filters

[6368]

I have a 96 rd with a fram filter housing and i have noticed that other rd's have a larger donaldson filter housing. is this just a differnce in years or a difference in the size of the engine. which filter has the best capacity ? also that little restriction gauge on the side of the filter housing never moves. i thought it was broken so i took it off and put vacuum to it and it moves:although i'am unsure as to what specific level of vacuum indicates its time to change the filter. i just change the filter every 600 hrs. Is this ok?

[Rob]

I have a 96 rd with a fram filter housing and i have noticed that other rd's have a larger donaldson filter housing. is this just a differnce in years or a difference in the size of the engine. which filter has the best capacity ? also that little restriction gauge on the side of the filter housing never moves. i thought it was broken so i took it off and put vacuum to it and it moves:although i'am unsure as to what specific level of vacuum indicates its time to change the filter. i just change the filter every 600 hrs. Is this ok?

I think I have that same filter housing on my R-795. It is about 4 inches smaller in diameter than the larger Donaldson units. Mine has been replaced and is not original to the truck.

I can't say with absolute certainty but if the filter housing is original to the chassis it should be fine. Larger is not always better. Physically larger will hold more dirt before replacement. Making the assumption that it takes more fuel, and air to make horsepower, the filter housing, (if original to the truck with a 350 horse engine) should be sized properly for the design criteria in which it operates.

The filter restriction gauge that is on the side of the unit is an indicator that is calibrated to show a red band, (it should be currently yellow, white, or clear) when the element requires replacement. A "Bourdon Tube" gauge calibrated in inches of water column is much more sensitive to vacume changes and will give the subsequent meter deflection you mention. Filter medias from manufacturers rate filter restrictions and ratings at different levels. It is best to consult the websites for the elements to have accurate representation of when to change. I prefer an in dash gauge for filter restriction. The type you have that mounts into the side of the filter enclosure simply "trips" and shows the red bar when it's set point is reached. A gauge that you can see in, or under the dashboard is instantaneous and "live" when you accelerate.

Hopefully this information is of use to you.

Plenty of answers to be had from this group, just ask.

Rob