Oil Bath Air Cleaner - '40 Buick

[kingrudy]

I have got my oil bath air cleaner almost ready to install, but I have heard mixed opinions as to using a paper filter, or keeping it as an oil bath cleaner. I tried the local auto parts store and was not able to find the correct size. I would welcome input on this, as I am really a rookie.

 

Thanks,

 

Mike

 

1940 Super Coupe

[Guest]

Use it as it was designed.  Other than a bit messy to clean when required it is a superior filtering method.

[kingrudy]

Thanks for the reply, I have heard both good and bad about the oil bath filter. I think that I will try it both ways and see what works best. I realize the the oil filtration should work well, just not sure about the regular maintenance.

[kgreen]

The oil bath was designed for use when dirt roads were more prevalent and addressed the concern for filtration under those driving conditions.  Paper filtration can work equally well in a housing designed to hold a paper media filter but you would have to understand the difference in air flow conditions through the the filter housing that was designed for oil bath versus a paper filter designed for a different flow conditions.  The first thing I would do is look at the application that the filter was designed for.  If it was for a 1200 cc four cylinder engine (about 73 cu in), you know that the air flow through a 248 cu in 8 cylinder engine would be drastically different.  Filters are designed to contain particles, a smaller filter can plug up faster.  If the smaller filter plugs up faster will you starve the engine of air at higher rpms? The higher flow rate through the filter can lead to higher impaction forces, can the filter handle that?  In short, just becasue the paper filter fit doesn't mean that it will give you desired performance.

 

Two presumptions about todays drive: 1) you won't likely use the car on dirt roads and 2) Dirt or paved, the car is not likely to see more than 20,000 miles driven under your ownership.  You might even get away using no filter, though I would not recommend that.

[kingrudy]

Thanks Ken, I have taken into account the size of the media and density to achieve a good amount of flow through the carburetor  and will consider that I may have to change this more often, maybe once a season. I considered no filter for a brief amount of time, but I would be worried about foreign matter entering and fouling the carburetor and engine. I like the thought about the design and I will reference this and maybe even reach out to Fram technical support. Good to hear from you.

[kingrudy]

I spoke to the technical support at Fram, not the first guy, the expert that has been there since the fifties. He said that they used to make a conversion kit back in the fifties, but they stopped because there isn't enough demand. He couldn't see why this would not work as there is sufficient media to provide proper air flow and it seals properly so larger particulates cannot bypass the filter. So I'm going to give it a try, the filter is 3" tall by 7" outside diameter.

[Matt Harwood]

If it ain't broke...

 

It's often a mistake to assume that just because we have an additional 80 years of technology and learning behind us that we know more than the factory engineers about how a vintage car should work. This might be time and effort better spent elsewhere on the car rather than trying to re-engineer something that has worked reliably for decades. Best of all, you don't have to buy a new filter every time you clean it. Just clean it and add a splash of leftover oil.

 

Besides, oil bath air filters with paper filters in them always look hackey and homemade:

 

 

[kingrudy]

Well I think that I'm going to have to agree to disagree with you on this. I just retired from working as the Facility Manager at a large hospital this past year after 25 years, I only mention this because air quality was extremely important to all areas of the facility especially the surgical suites. Air Filters are given a MERV (Minimum Efficiency Reporting Value) rating, your house has an 11 or 12 MERV rating. Over my 25 years air quality standards got stricter and a MERV rating of 18 was the gold standard. The Air Handlers were 30 years old and were designed for filters that allowed larger particulates to pass through, but standards changed (Joint Commission). I bring this up as I would like to have the components of my engine last as long as possible and if giving the engine a better air quality will help this along, then I will use the paper filter sacrifice looks. I don't plan on throwing the wire mesh away, but as a daily driver I will try to provide the best air quality possible.

 

Mike

BCA 44810

Lic. LA City Steam Engineer and Detroit Steam Engineer

[Matt Harwood]

I don't doubt your credentials, I just wonder about the need to re-engineer a system like this where the original is already pretty effective. Besides, it's going on a low-compression, low-RPM, gently-driven machine with pretty loose tolerances that has spent the last 80 years sucking air through the oil bath air cleaner without ill effects. Installing a state-of-the-art filtration system now kind of seems like closing the gate after the cows have wandered off, no? I understand that it's your preference and your area of expertise, but these cars lasted tens, if not hundreds of thousands of miles in much harsher conditions with far inferior oils and yes, these oil bath filters. I drive my cars regularly (my '41 Limited is my daily driver from May to October) and don't expect to wear out the engine from sucking dirty air. I'm not driving on dirt roads and modern oils are far superior at holding particulates in suspension rather than letting them grind on cylinder walls. I'm also a bit more careful than the guys who were ramming around in these cars in, say, the 1950s and 1960s when they were just cheap used cars that they could throw away when they were done. An engine isn't an intensive care patient with delicate lungs--it's a machine designed to work under adverse conditions and the oil bath was effective enough that it is still in use on commercial vehicles used in harsh environments (like large farm equipment). Your engine doesn't care and won't be hurt by whatever dust manages to get past the oil bath. I do not believe you will add any measurable life to the engine with a different air filter, no matter how good. 

 

My comment was only to suggest that you're past the point of diminishing returns in redesigning the air filter unit. I'm not criticizing you or saying that you're wrong, just suggesting that your time and resources could be more productive elsewhere if they are, like they are for most of us, finite. You asked for advice as a rookie with no experience with these cars, so I responded as someone who has been driving and working on these cars for decades, and that's my advice. You don't need to listen to me, it makes no difference and you certainly won't hurt anything by changing the filter. I just don't know if your gains will be measurable, either. No harm, no foul here. Do as you like.

[Ben Bruce aka First Born]

Mike, In am with you. I am no engineer. Far from it, just school of hard knocks. I use the paper and will continue to do so. I drove Semi trucks for 40+ years and they had all changed to paper early in that time frame. Matt may be right, but I expect the oil was used because it was the best available at the time. Times do change.

 

  Ben

[kingrudy]

To make a long story nauseating, as my old boss once said to me.  Changes in technology are constant, oil filters were a recent addition to the car when this model was introduced, so to provide cleaner air to the carb seems to make sense given the small expense and time involved. So I think that I will use the paper filter on a daily basis and use the wire mesh for show.

[rodneybeauchamp]

I used to sell Donaldson air cleaner systems for automotive, industrial and agricultural equipment. When sizing up the right air cleaner for an engine we used a chart to calculate the amount of air in CFM required.

 

The chart used the engine displacement and the maximum governed RPM to obtain a value.  Petrol engines were based at around 85% efficiency, therefore 85% of the value, diesel  engines a bit more and turbocharged and supercharged engines more again ( I think almost twice the value of the volume calculated)

 

So when sizing  any filter media you want to use, perhaps try to ascertain the airflow requirements of what engine you have already and make sure the filter will pass that amount of air. Take into account any bends or restrictions in the inlet and outlet to the carby, Otherwise it will restrict airflow and cause other issues you won’t need.

 

Using an air cleaner off a 60s petrol engine of similar displacement should work fine. I used a 60’s Valiant slant six on a 1940 sidevalve six Pontiac with good success as the original oil bath was long gone. It looked plain and simple in black, no air snorkel as the lid was larger than the base, allowing good air flow without restriction.

 

It was similar to this.

just my two bobs worth from down under. ?????

 

 

[avgwarhawk]

Oil as the filter medium for the intake/carb could also have gone the way of the dinosaur as a result of the environment concerns.  However, there are performance air filters on the market today that are paper and  sprayed with oil(K&N) .  I would think the oil would play a part in keeping particulate matter out of the engine and with some efficiency. 

 

I run the oil filter on top of my Carter carb.   I keep it this way as it works as designed and well from my experience.   The little miles I drive each year it does not require cleaning but once every two years.    

 

As a side note, when I shut down my engine on my 1960 paper filter set up I always have a strong gas odor as the gas vapor finds its way to the snorkel on the  air cleaner housing.   I do not experience this with the oil filled air cleaner housing without snorkel/paper filter.     

[kingrudy]

Thanks for all of the input, Rodney's post got me doing a little more research and I stumbled across this site: http://www.onallcylinders.com/2013/11/27/match-air-filter-size-engine/. This is a great article that talks about supplying an adequate amount of clean air to the engine. The formula begins with providing the area of the filter media (A= CID x RPM) by multiplying the Cubic inch of the engine times the RPM at maximum horse power. I have a 263 and the maximum horsepower is 3600 @ 124 HP (engine is RE). To get the height of the filter divide Area by ( Diameter x 3.14) + .75.  I got the diameter using the greatest that would fit in the existing housing 7 inches multiply times pi and add .75 for the rubber gaskets on the filter. It all looks like this: A= 263 x 3600 / 25,500 = 37.129 then,

H = 37.129/(6.9 x 3.14) + .75 = 1.66. I used a 3" filter height instead of the 1.66 to account for restrictions in the air flow as the calculations don't seem to account for that. Just a thought.... 

[rodneybeauchamp]

2 hours ago, kingrudy said:

I used a 3" filter height instead of the 1.66 to account for restrictions in the air flow as the calculations don't seem to account for that. Just a thought.... 

 

Mike,

Interested in what the filter part number you found that fits the housing.

 

And Any chance of some pics of the finished air cleaner?

thanks

Rodney ?????

[kingrudy]

Hello Rodney,

Here are the before and after photos. The filter looks larger in the after photo, but I think that is because of the angle that I used (no pro photographer here). The filter is a Fram CA8507 and it is 6.9 x 3. The math says that you could use a 7 x 1.66 but I chose the 3" tall filter to account for the air flow restrictions (probably over sized). I haven't mounted it on the carb, as I still have some details that I'm working on in the engine compartment. I do have the smaller filter, which is a Fram CA6605, 7" x 1-3/4, should work and look a little neater. Good luck.

Mike