The Ford Barn

olut · 05-30-2017, 10:33 AM

Short description:
35-A with original Zenith, air filter attached last fall, worked well, no significant loss of power, did not run rich or lean, ambient temperature below 80s.

The past two days we have high summer with temperatures in the 90ies, all fine when engine is cold, but as soon as the baby is getting warm, engine wants to die when accelerating, backfires and stops misbehaving only at low RPM, adjustments on the GAV dont resolve the problem.

So I removed the air filter and all is perfect.

Reason: that carb is not "air balanced" to be used with an airfilter (like those in my other babies 76-A and 165-D), cold intake air has less volume than hot intake air, if there is a certain flow rate limit at the filter and this is been exceeded due the high intake air temperature (close at the exhaust flange), then the carb should mix rich, but backfiring is always an effect of lean mixture......
...sounds not realy logic, where is the error in my point of view ?
...any thoughts ??

Best Greetings from hot Vienna

Dick Steinkamp · 05-30-2017, 11:16 AM

Quote:

Originally Posted by olut

cold intake air has less volume than hot intake air,

I think that's backwards. Cold air is MORE dense than hot air...

https://en.wikipedia.org/wiki/Density_of_air

160B · 05-30-2017, 11:27 AM

Quote:

Originally Posted by olut

Short description:
............................

So I removed the air filter and all is perfect.

.................

What kind of air filter, paper, K&N?

Can you post a photo of the air cleaner you removed?

SeaSlugs · 05-30-2017, 11:31 AM

Quote:

Originally Posted by Dick Steinkamp

I think that's backwards. Cold air is MORE dense than hot air...

https://en.wikipedia.org/wiki/Density_of_air

yup - heard of an old trick of race cars they would dump dry ice in the air box to added oomph. Dont know how true that is or not...

160B · 05-30-2017, 11:38 AM

Info from MODEL-A.org

http://www.model-a.org/filtering_air_into_carb.html

Carburetors, with their air input totally unfiltered, suck in all kinds of stuff that can do damage to your engine. Fine silica dust and powdered rock are the most common materials that are pulled in and cause engine wear.

The Air Maze, metal gauze unit (sold by most Model A Ford part distributors; shown on the left) prevents large particles from entering, but does nothing to filter out the small stuff that most commonly causes the damage.

The next logical step is to try paper element cartridges. However, you have to be careful not to restrict the air to fuel balance of the carburetor. The level of air resistances varies depending on the size, surface area, and the physical attributes of the filtering material.

An undersized filter restricts airflow into the carburetor and lowers the pressure at the choke. These consequences make the fuel-air ratio higher (too much gasoline for the airflow reduction) and also lower the velocity of fuel flow through the Venturi (reducing engine responsiveness to throttling). The result is carbon deposits in your engine from the rich mixture.

One needs to consider the air volume needs for a nominal 200 cubic inch engine at 2,800 RPM and the carburetors air intake area of 1.767 square inches. You also have to consider how much to oversize the filter element to allow for clogging up to say 30%. With some rough calculations, you'll find that you need a large filter.

I've read material from multiple sources, which say: "automotive engineers regularly size air filter surface areas at one-half an engines cubic inch capacity", which is 100 square inches for the nominal Model A engine.

I have found paper filters clog up quickly, restrict flow, and retain gasoline from drippy carburetors for a long time. So, I prefer K&N washable, oilable and reusable filters. Using published K&N formulas, I calculated the filter required for a typical Model A engine. If your engine has been modified to increase the cubic inches, you will want to adapt my following calculations.

First, I calculated the Effective Filtering Area for the physical attributes of K&N filter materials:

200 Cubic inches displacement times 2,800 RPM divided by 20,839, which is the factor for K&N Filter Attributes = 26.9 square inch Effective Filtering Area.

Then, I calculated the minimum length for a filter to fit in an Air Maze housing:

26.9 square inch Effective Filtering Area divided by (3 & 1/2 inch Air Maze diameter times 3.14 Pi) plus .75 inches to compensate for the rubber seals on each end of the element = 3.2 inches minimum filter length.

This is significantly longer than the very small air filters commonly seen on many Model A Fords.

K&N offers several filters that can be used with the Air Maze housing.
Part # E-3050 is 3.5 inches long.
Part # E-9257 is 5.5 inches long.
Part # E-2040 is 6.625 inches long.

To provide some margin for the filter getting dirty, before you get around to cleaning it, I would recommend the 5.5 inch long length. I know it is an over kill, but I am currently using the 6.625 inch long one to allow for driving on dusty gravel roads and to extend my time between filter cleaning / re-oiling cycles.

CAUTION: Regardless of any filter that you choose to use, you have to be watchful for a leaky carburetor that can load the filter up with gasoline and be vulnerable to ignition from the exhaust pipe and possibly cause a disastrous fire.

Important notes on the use of Air Maze housings:

When mounting an Air Maze housing onto a Zenith, Model A carburetor, it is important that a lock washer and nut be used to keep the screw from coming loose and allowing the Air Maze housing to fall to the ground. The screw and nut can be seen at the top of each photo.

To minimize air leaks at the point where an Air Maze connects to the Zenith, Model A carburetor, I use an o-ring (1-7/8" OD and 1-1/2" ID) on the carburetors air intake.

To use a long filter in the Air Maze, the large wing bolt needs to be replaced with a long 1/4 - 20 bolt or with a threaded rod, with nuts and lock washers.

1955cj5 · 05-30-2017, 12:17 PM

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Quote:

Originally Posted by Dick Steinkamp

I think that's backwards. Cold air is MORE dense than hot air...

https://en.wikipedia.org/wiki/Density_of_air

Cold air has more density but less volume for a specifc weight...thats why a warm balloon will shrink when cooled...

The 15:1 ratio that makes our engines run is based on weight, not volume.

Dick Steinkamp · 05-30-2017, 01:27 PM

Quote:

Originally Posted by 1955cj5

Cold air has more density but less volume for a specifc weight...thats why a warm balloon will shrink when cooled...

The 15:1 ratio that makes our engines run is based on weight, not volume.

I think we are agreeing? More weight (mass) in cold air than in the same volume of warm air. (Charles’s Law)

olut · 05-30-2017, 02:32 PM

that was the air filter I removed today, had no other option, otherwise would have had to trailer back my Model A...

https://www.macsautoparts.com/ford_m...sh-filter.html

olut · 05-30-2017, 02:48 PM

this is the setup in my RHD Fodor Town Sedan, the filter is in a much cooler area and does not make any trouble. I know, without an air filter you get a lot of stuff into the engine you don't want to know it there. So I ordered an air filter balance new carburetor from the US, but I need to be patient, it is on backorder....

Theoretically I can do the same air filter setup on my 35-A as well, although it is (now) a LHD, am I wrong ??

olut · 05-30-2017, 02:52 PM

thank you for this very informative facts, is´nt the paper filter having even more resistance than the mash filter ?
I am actually dealing with the combination of far too hot intake air through an air filter and combined with a non-air filter balanced Zenith.......

...what if I relocate the air filter more to the front near the radiator to get cooler air ??

Jason in TX · 05-30-2017, 02:53 PM

1932 Factory option. Very Rare. I just sold one here.

Y-Blockhead · 05-30-2017, 03:22 PM

Quote:

Originally Posted by olut

that was the air filter I removed today, had no other option, otherwise would have had to trailer back my Model A...

https://www.macsautoparts.com/ford_m...sh-filter.html

That paper filter is much to small and restrictive. As noted in the posted by 160B from modela.com you need a minimum 5.5" K&N.

160B · 05-30-2017, 04:47 PM

FWIW

I have the K&N E-3050 on both my Model A's and have close to 40,000 miles without any problems.

The info in the post from MODEL-A.org clearly states the minimum length should be 3.2 inches, and the E-3050 is 3.5 inches.

Also note the MODEL-A.org calculation is based on an engine RPM of 2800 RPM, I have a Mitchell overdrive and typically cruise around 2100 to 2200 RPM.

So as I see it the 3.5 inch filter is approximately 10% oversized and I run at 2200 rpm which is approximately 20% reduced cfm as your rpm goes down so the cfm through the carburetor. So the E-3050 is adequately sized unless you are cruising at 2800 RPM.

The post also notes "I know it is an over kill" for the 5.5 inch K&N.

Nabco · 05-30-2017, 05:59 PM

I was using an Air Maze and the car ran like crap so I took it off and she started running great, ran it without a filter all last summer but was worried about what I was sucking up into the engine. This spring I put a High Boy on her and she is running great, I think it has to do with the filter being up in the cooler air.

Jim Brierley · 05-31-2017, 11:35 AM

I have never run a filter on any of my A's, and put a minimum of 2,000 miles a year on them. I also live on a dirt road. Been doing this since 1958. Engines show no signs of abnormal wear. If it ain't broke, don't fix it.

SeaSlugs · 05-31-2017, 11:45 AM

Quote:

Originally Posted by Jim Brierley

I have never run a filter on any of my A's, and put a minimum of 2,000 miles a year on them. I also live on a dirt road. Been doing this since 1958. Engines show no signs of abnormal wear. If it ain't broke, don't fix it.

I wonder how much dust it actually sucks up. I live in farm country so planting/ harvest seasons theres ALOT of dust in the air (looks like a sand storm you see in arizona) or if your following a car on one of those dirt/rock roads it kicks up an amazing amount. Its gonna pass right thru the radiator but I wonder how much is actually reverse sucked into the engine since the intake is rear facing...

I mean if it sucked up cinders or small pebbles sure I can see the damage done but clay dust has been a thickener in many oils thru the years and cant see what damage it could do.

George Miller · 05-31-2017, 11:46 AM

I.m with Jim. I also have been running Model A's since the 60ts. No air filter.
My 28 coupe 28,000 on the engine when I sold it last month. Used no oil, ran great, never had to add water.

Peyton · 05-31-2017, 12:44 PM

Just wrap and secure a home air conditioner vent filter (Lowes) around the mesh on an air maze. I believe the size is 4" by 8". I use a wire catch to affix the filter to the mesh.

Does not seem to restrict my Tillotson and gets quite dirty within a relatively short time. That suggests that it is catching a lot of dirt.

olut · 05-31-2017, 02:23 PM

...I just ordered a high boy, will see, how that is going to work...

thank you guys for all your input

Nabco · 05-31-2017, 02:30 PM

Quote:

Originally Posted by olut

...I just ordered a high boy, will see, how that is going to work...

thank you guys for all your input

Be sure to let us know.....

05-30-2017, 10:33 AM	#1
olut Member Join Date: Mar 2014 Location: Vienna, Austria, Europe Posts: 87	Air Filter - or - not to filter the air ? Short description: 35-A with original Zenith, air filter attached last fall, worked well, no significant loss of power, did not run rich or lean, ambient temperature below 80s. The past two days we have high summer with temperatures in the 90ies, all fine when engine is cold, but as soon as the baby is getting warm, engine wants to die when accelerating, backfires and stops misbehaving only at low RPM, adjustments on the GAV dont resolve the problem. So I removed the air filter and all is perfect. Reason: that carb is not "air balanced" to be used with an airfilter (like those in my other babies 76-A and 165-D), cold intake air has less volume than hot intake air, if there is a certain flow rate limit at the filter and this is been exceeded due the high intake air temperature (close at the exhaust flange), then the carb should mix rich, but backfiring is always an effect of lean mixture...... ...sounds not realy logic, where is the error in my point of view ? ...any thoughts ?? Best Greetings from hot Vienna __________________ the best medicine to avoid mid life crisis.....

05-30-2017, 11:38 AM	#5
160B Senior Member Join Date: Aug 2010 Location: Port Orchard, WA Posts: 1,498	Re: Air Filter - or - not to filter the air ? Info from MODEL-A.org http://www.model-a.org/filtering_air_into_carb.html Carburetors, with their air input totally unfiltered, suck in all kinds of stuff that can do damage to your engine. Fine silica dust and powdered rock are the most common materials that are pulled in and cause engine wear. The Air Maze, metal gauze unit (sold by most Model A Ford part distributors; shown on the left) prevents large particles from entering, but does nothing to filter out the small stuff that most commonly causes the damage. The next logical step is to try paper element cartridges. However, you have to be careful not to restrict the air to fuel balance of the carburetor. The level of air resistances varies depending on the size, surface area, and the physical attributes of the filtering material. An undersized filter restricts airflow into the carburetor and lowers the pressure at the choke. These consequences make the fuel-air ratio higher (too much gasoline for the airflow reduction) and also lower the velocity of fuel flow through the Venturi (reducing engine responsiveness to throttling). The result is carbon deposits in your engine from the rich mixture. One needs to consider the air volume needs for a nominal 200 cubic inch engine at 2,800 RPM and the carburetors air intake area of 1.767 square inches. You also have to consider how much to oversize the filter element to allow for clogging up to say 30%. With some rough calculations, you'll find that you need a large filter. I've read material from multiple sources, which say: "automotive engineers regularly size air filter surface areas at one-half an engines cubic inch capacity", which is 100 square inches for the nominal Model A engine. I have found paper filters clog up quickly, restrict flow, and retain gasoline from drippy carburetors for a long time. So, I prefer K&N washable, oilable and reusable filters. Using published K&N formulas, I calculated the filter required for a typical Model A engine. If your engine has been modified to increase the cubic inches, you will want to adapt my following calculations. First, I calculated the Effective Filtering Area for the physical attributes of K&N filter materials: 200 Cubic inches displacement times 2,800 RPM divided by 20,839, which is the factor for K&N Filter Attributes = 26.9 square inch Effective Filtering Area. Then, I calculated the minimum length for a filter to fit in an Air Maze housing: 26.9 square inch Effective Filtering Area divided by (3 & 1/2 inch Air Maze diameter times 3.14 Pi) plus .75 inches to compensate for the rubber seals on each end of the element = 3.2 inches minimum filter length. This is significantly longer than the very small air filters commonly seen on many Model A Fords. K&N offers several filters that can be used with the Air Maze housing. Part # E-3050 is 3.5 inches long. Part # E-9257 is 5.5 inches long. Part # E-2040 is 6.625 inches long. To provide some margin for the filter getting dirty, before you get around to cleaning it, I would recommend the 5.5 inch long length. I know it is an over kill, but I am currently using the 6.625 inch long one to allow for driving on dusty gravel roads and to extend my time between filter cleaning / re-oiling cycles. CAUTION: Regardless of any filter that you choose to use, you have to be watchful for a leaky carburetor that can load the filter up with gasoline and be vulnerable to ignition from the exhaust pipe and possibly cause a disastrous fire. Important notes on the use of Air Maze housings: When mounting an Air Maze housing onto a Zenith, Model A carburetor, it is important that a lock washer and nut be used to keep the screw from coming loose and allowing the Air Maze housing to fall to the ground. The screw and nut can be seen at the top of each photo. To minimize air leaks at the point where an Air Maze connects to the Zenith, Model A carburetor, I use an o-ring (1-7/8" OD and 1-1/2" ID) on the carburetors air intake. To use a long filter in the Air Maze, the large wing bolt needs to be replaced with a long 1/4 - 20 bolt or with a threaded rod, with nuts and lock washers. __________________ 1931 160B & 1931 68B If you don't have time to do it right the 1st time, how do you have time to do it the 2nd time?

05-30-2017, 02:32 PM	#8
olut Member Join Date: Mar 2014 Location: Vienna, Austria, Europe Posts: 87	Re: Air Filter - or - not to filter the air ? that was the air filter I removed today, had no other option, otherwise would have had to trailer back my Model A... https://www.macsautoparts.com/ford_m...sh-filter.html __________________ the best medicine to avoid mid life crisis.....

05-30-2017, 02:52 PM	#10
olut Member Join Date: Mar 2014 Location: Vienna, Austria, Europe Posts: 87	Re: Air Filter - or - not to filter the air ? thank you for this very informative facts, is´nt the paper filter having even more resistance than the mash filter ? I am actually dealing with the combination of far too hot intake air through an air filter and combined with a non-air filter balanced Zenith....... ...what if I relocate the air filter more to the front near the radiator to get cooler air ?? __________________ the best medicine to avoid mid life crisis.....

05-30-2017, 02:53 PM	#11
Jason in TX Senior Member Join Date: May 2010 Location: ⓉⒺXⒶⓈ Posts: 2,047	Re: Air Filter - or - not to filter the air ? 1932 Factory option. Very Rare. I just sold one here. __________________ -------------- Drive it like you know how to fix it! DMAFC / OILERS CC-MC

05-30-2017, 04:47 PM	#13
160B Senior Member Join Date: Aug 2010 Location: Port Orchard, WA Posts: 1,498	Re: Air Filter - or - not to filter the air ? FWIW I have the K&N E-3050 on both my Model A's and have close to 40,000 miles without any problems. The info in the post from MODEL-A.org clearly states the minimum length should be 3.2 inches, and the E-3050 is 3.5 inches. Also note the MODEL-A.org calculation is based on an engine RPM of 2800 RPM, I have a Mitchell overdrive and typically cruise around 2100 to 2200 RPM. So as I see it the 3.5 inch filter is approximately 10% oversized and I run at 2200 rpm which is approximately 20% reduced cfm as your rpm goes down so the cfm through the carburetor. So the E-3050 is adequately sized unless you are cruising at 2800 RPM. The post also notes "I know it is an over kill" for the 5.5 inch K&N. __________________ 1931 160B & 1931 68B If you don't have time to do it right the 1st time, how do you have time to do it the 2nd time?

05-30-2017, 05:59 PM	#14
Nabco Senior Member Join Date: Jul 2014 Location: Dublin, OH & Clyde, NC Posts: 494	Re: Air Filter - or - not to filter the air ? I was using an Air Maze and the car ran like crap so I took it off and she started running great, ran it without a filter all last summer but was worried about what I was sucking up into the engine. This spring I put a High Boy on her and she is running great, I think it has to do with the filter being up in the cooler air. __________________ 1930 Deluxe Coupe "Sister"

05-31-2017, 11:35 AM	#15
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,321	Re: Air Filter - or - not to filter the air ? I have never run a filter on any of my A's, and put a minimum of 2,000 miles a year on them. I also live on a dirt road. Been doing this since 1958. Engines show no signs of abnormal wear. If it ain't broke, don't fix it.

05-31-2017, 11:46 AM	#17
George Miller Senior Member Join Date: May 2010 Location: NC Posts: 2,975	Re: Air Filter - or - not to filter the air ? I.m with Jim. I also have been running Model A's since the 60ts. No air filter. My 28 coupe 28,000 on the engine when I sold it last month. Used no oil, ran great, never had to add water.

05-31-2017, 12:44 PM	#18
Peyton Senior Member Join Date: May 2010 Location: Jacksonville Fl Posts: 152	Re: Air Filter - or - not to filter the air ? Just wrap and secure a home air conditioner vent filter (Lowes) around the mesh on an air maze. I believe the size is 4" by 8". I use a wire catch to affix the filter to the mesh. Does not seem to restrict my Tillotson and gets quite dirty within a relatively short time. That suggests that it is catching a lot of dirt.

05-31-2017, 02:23 PM	#19
olut Member Join Date: Mar 2014 Location: Vienna, Austria, Europe Posts: 87	Re: Air Filter - or - not to filter the air ? ...I just ordered a high boy, will see, how that is going to work... thank you guys for all your input __________________ the best medicine to avoid mid life crisis.....