Oil bath shows as an option in the materials I have thru '71, but I don't have the '72 or '73 books. It isn't listed as an option in the '74 and up books. Fun to see one out there. Does it show up on the Marti?
Yeah, oil bath filters hold more than the paper of the era did but they also let a LOT more dirt through. I did some research on air filters for a story and collected a bunch of SAE white papers from various eras to get historical information on the efficiency of the air filters of various types in various eras back to when air filters started to get common in the 1920s. In the '60s, the average oil bath was at about 85% efficiency on coarse test dust while a paper filter was 95+. In more recent times, air filters are in the 98+% initial efficiency. Some are in the 99% range. In the 1920s, they bragged about 50% efficiency
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Other interesting facts about oil bath filters is that their efficiency goes down with the oil level. Let the oil get low or run out, you may as well not have the filter on in the first place (like running an uncoiled K&N). They are also very restrictive, but if you lower the oil level, it reduces restriction. In the '90s, I spent some time at the K&N lab running restriction tests on air filter assemblies from various makes. Two oil bath units were in the mix, one from a '60s Jeep and the other from a '70s Land Rover. Holy Crap! Those two oil bath filters barely flowed enough air for the engine to make rated power. The old oil bath and early paper filter era is when an air filter housing change just about guaranteed an increase in power, even on a stock engine. Experienced that myself back in the day and if you removed an oil bath (and many paper too) there was enough of a change in carb calibration that you had to rejet the carb (usually one or two sizes larger on the main jet, sometimes a size or two on an air jet... depending on the carb). Carb would go way lean and you could burn a valve. In one case, it was enough that the engine stumbled on acceleration and had a high speed lean miss.