I have been impressed with the intelligentsia found here in the Ford Barn, so I thought I'd pose this question here. Will an inline fuel filter have better fuel flow with a filter that has a low macron rating or a high macron rating? Example. I have seen them with a macron rating of 10 and I have seen the with a macron rating of 150. In the end I'm looking for a less restrictive filter. Thank you very much Gino
Fuel filter- macrons
- Thread starter Gino
- Start date
jmeckel
Well-known member
There is more to a filter than micron size, onother one is free flow rate.
The direct answer to your question is the smaller the micron number the smaller the partical that can go past, so all things being equal the smaller number would have more restriction and lower flow rate. However all filters are not designed the same, and surface area of filteration has a lot to do with flow rate as does the filter material...... etc..... There are other better options than a inline filter, cleaning tank, screen filter in tank outlet, "dirty leg" search on FB for how that is done, if you have a glass fuel filter there is a filter that fits inside of the glass bowl..... that is some of the other ways of dealing with the issue ....
The direct answer to your question is the smaller the micron number the smaller the partical that can go past, so all things being equal the smaller number would have more restriction and lower flow rate. However all filters are not designed the same, and surface area of filteration has a lot to do with flow rate as does the filter material...... etc..... There are other better options than a inline filter, cleaning tank, screen filter in tank outlet, "dirty leg" search on FB for how that is done, if you have a glass fuel filter there is a filter that fits inside of the glass bowl..... that is some of the other ways of dealing with the issue ....
MikeK
Well-known member
What is a "macron"? I only know of it a a diacritic indicating a long vowel sound. If you are referring to micron, a non-SI unit indicating a millionth of a meter, that rating has nothing to do with flow resistance.
In filters it only indicates the average size of the smallest particle it will trap. A larger micron rating filter will pass larger particles and may or may not be less restrictive to flow at a given pressure differential, even if the exterior form of the housings appear identical. Flow resistance is a complex function of the total flow pathways, their shape, length, material to media molecular adhesion, and several other factors.
Fuel filters for small engines with gravity feed tanks, like lawn mowers, etc. are generally less restrictive than filters designed for pressure apps at relatively low flow rates, BUT they do not necessarily provide a high enough fuel flow for an engine that produces 50 horsepower.
Rather than worrying about the micron rating I think I would ask other fordbarners, from experience, which filters have worked for use on their A's, and how they work uphill at full throttle.
Keep in mind that the flow resistance of any filter will quickly increase as it accumulates the tiniest bit of fines.
In filters it only indicates the average size of the smallest particle it will trap. A larger micron rating filter will pass larger particles and may or may not be less restrictive to flow at a given pressure differential, even if the exterior form of the housings appear identical. Flow resistance is a complex function of the total flow pathways, their shape, length, material to media molecular adhesion, and several other factors.
Fuel filters for small engines with gravity feed tanks, like lawn mowers, etc. are generally less restrictive than filters designed for pressure apps at relatively low flow rates, BUT they do not necessarily provide a high enough fuel flow for an engine that produces 50 horsepower.
Rather than worrying about the micron rating I think I would ask other fordbarners, from experience, which filters have worked for use on their A's, and how they work uphill at full throttle.
Keep in mind that the flow resistance of any filter will quickly increase as it accumulates the tiniest bit of fines.
Kevin in NJ
Well-known member
The A is designed to suck dirt.
Use all original filters and the original carb and you will be fine. You can easily check for dirt in the original carb just by taking the one bolt loose.
How do I know it works?
My 30 fordor would clog from the rust flakes settling at the bottom. I flush the tank several times to get rid of most of the stuff. Then I stuck a short piece of pipe on the inlet to the valve so the dirt will get slowly sucked through the system and cleaned out of the tank.
The first couple of tanks ended up with a good pile in the fuel bowl (I switched to glass bowl to monitor). Never anything in the carb or at the carb filter. The amount of dirt quickly slowed down to a small amount after the first few tanks.
If you have the original (not repro, never used them so I do not know) filter screens and the original carb then you have NO need for an external filter. Trust that Ford did a good job, remember things were much dirtier back then.
Other carbs are not so forgiving with dirt so that is why I am specific on the original carb and no extra filters. Some of what I read indicates the other carbs do not like to eat dirt, never used one so I do not know.
Use all original filters and the original carb and you will be fine. You can easily check for dirt in the original carb just by taking the one bolt loose.
How do I know it works?
My 30 fordor would clog from the rust flakes settling at the bottom. I flush the tank several times to get rid of most of the stuff. Then I stuck a short piece of pipe on the inlet to the valve so the dirt will get slowly sucked through the system and cleaned out of the tank.
The first couple of tanks ended up with a good pile in the fuel bowl (I switched to glass bowl to monitor). Never anything in the carb or at the carb filter. The amount of dirt quickly slowed down to a small amount after the first few tanks.
If you have the original (not repro, never used them so I do not know) filter screens and the original carb then you have NO need for an external filter. Trust that Ford did a good job, remember things were much dirtier back then.
Other carbs are not so forgiving with dirt so that is why I am specific on the original carb and no extra filters. Some of what I read indicates the other carbs do not like to eat dirt, never used one so I do not know.
jmeckel
Well-known member
Another point. Assuming you have a original type Zenith carb, make sure that there is a good screen filter in the carb. I rebuild carbs and at least 50% of them show up with just the nut left, the screen is long gone. This is a cheap and fast fix. And a very good filter. Just as Ford / Zenith designed it to be.
Below is a picture of the original type Zenith carb screen.
Below is a picture of the original type Zenith carb screen.
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Mike V. Florida
Well-known member
here it is
As for an inline filter stick to a filter that is used in gravity fed motorcycles as mentioned above for best results.
Bill Goddard
Well-known member
With some of the older originals or repos - I don't know which - the brass end fittings at the left end of the part in the picture are undersized and can let unfiltered fuel into the carb (go around the filter). Building up the diameter size with solder and hand fitting or lapping the fit would help. Maybe an ethanol resistant O ring could be dropped in first? Bill GAnother point. Assuming you have a original type Zenith carb, make sure that there is a good screen filter in the carb. I rebuild carbs and at least 50% of them show up with just the nut left, the screen is long gone. This is a cheap and fast fix. And a very good filter. Just as Ford / Zenith designed it to be.
Below is a picture of the original type Zenith carb screen.
Tacoma Bob
Well-known member
I run the same set up as Mitch. Many thousands of trouble free driving.
Purdy Swoft
Well-known member
Besides the original style filters used in the cast iron sediment bowl and Zenith carburetor, I only use the pencil or stand up filter that installs in the cut off valve. I feel that the standupo filter pictured in post # 9 is the only additional filter that is needed. I avoid any micro filter and have had problems with them. Beware that there may still be micro versions of the pencil or stand up filters, this is the type that I had trouble with. Small particles that would pass through the careburetor with no problem will stop up and block flow through any micro type filter. I'm not familiar with micron numbers and only use mesh type filters. In line filters can be a fire hazard
Thanks for all the advice. I'll let it be known that I am a builder not a mechanic, but I'm learning. I do have and employ all the required screen filters and as of yet I do not have any carb problems. However if a modern trouble free in line filter could be installed I would certainly use it. Please note my two A's are drivers, and I drive them every day every where. I guess I have the Model A Flu. Good and smart folk here thanks again.
I just got one from Mikes affordable