fuel filter placement

[rockinrich]

I bought two fuel filters,one is a k&n see through 100 micron filter,the other is a sister company of k&n called spectre performance and it is a see through 40 micron filter.I was recommended that size micron for carbureted engines by summit.Both have 3/8/inlet/outlets and have replaceable filters.I plan on putting the 100 micron filter in front of both tanks that way you collect crap from both tanks for those of us that have dual tanks.The second filter,40 micron,i plan on putting between the mechanical fuel pump and the carburetor. i think for now i am going to run 5/16 fuel line since i have a stock engine right now and i was going to use 3/8 rubber at the bend coming off the fuel switch valve till straight and then install the 100 micron filter and then a small piece of 3/8 rubber on the outlet side, then install a brass 3/8 to 5/16 reducer connected to 5/16 fuel line to the engine bay and then again, 5/16 to 3/8 brass fitting and then 3/8 rubber before and after The second 40 micron filter to the carburetor.Thoughts?

 

[blubuckaroo]

A filter ahead of the mechanical pump isn't a good idea. The lower pressure it can create in the fuel line can contribute to vapor lock.
Two filters won't make the fuel any cleaner anyway.

 

[Broncobowsher]

Stock, there is a sock on the inlet inside the fuel tank. That is the pre-filter. By now most have broken and fallen off leaving an open tube for the pickup. That is where the 100 micron prefilter come into play. Also most aftermarket fuel tanks don't have any prefilter/sock. So a coarse pre filter is still a good idea. Alternate version of the stock design. If it clogs, easier to change than dropping the tank to change the sock.

I personally go for a finer post pump filter.

Now the micron rating isn't the whole story. Surface area also matters. A fine filter can flow a lot if there is the surface area to support it. A coarse filter can choke if it is too small
https://aeromotiveinc.com/wp-content/uploads/2022/07/101-Fuel-Filtration.pdf

 

[rockinrich]

A filter ahead of the mechanical pump isn't a good idea. The lower pressure it can create in the fuel line can contribute to vapor lock.
Two filters won't make the fuel any cleaner anyway.

Thanks for your help,do you mean the filter before the fuel pump, the 100 micron filter?

 

[rockinrich]

Stock, there is a sock on the inlet inside the fuel tank. That is the pre-filter. By now most have broken and fallen off leaving an open tube for the pickup. That is where the 100 micron prefilter come into play. Also most aftermarket fuel tanks don't have any prefilter/sock. So a coarse pre filter is still a good idea. Alternate version of the stock design. If it clogs, easier to change than dropping the tank to change the sock.

I personally go for a finer post pump filter.

Now the micron rating isn't the whole story. Surface area also matters. A fine filter can flow a lot if there is the surface area to support it. A coarse filter can choke if it is too small
https://aeromotiveinc.com/wp-content/uploads/2022/07/101-Fuel-Filtration.pdf

thank you for the help,i recently purchased two new sending units from toms,so is the 100 micron filter before the pump overkill?

 

[Broncobowsher]

If you know you have a fresh sock on the pickup, I would skip the 100 Micron.

 

[rockinrich]

If you know you have a fresh sock on the pickup, I would skip the 100 Micron.

so can the 100 micron actually restrict fuel flow and if so would you just go with the 40 micron after the fuel pump?

 

[Broncobowsher]

For the 100 to restrict, I reference the Aeromotive link above.
Still want a good filter after the pump

 

[rockinrich]

For the 100 to restrict, I reference the Aeromotive link above.
Still want a good filter after the pump

oh i missed that i will check out the link,thank you.Oh and is a 40 micron good enough with a carburetor?

 

[rockinrich]

interesting read for sure, here are a couple pics of the filters i bought the red one is the 100 micron and the white one is the 40 micron,thoughts?

 

[4xfun]

If you have a new sock on the pickup, it will last a long time. As far as the inline filter is concerned, Is that a glass or plastic cover? A rock or some other debris hitting the bottom of the truck could break a glass cover. Why not plumb in a larger canister filter or something like Ford had on the early 90's 302? Take a look at WIX 33027. Cheap and easy to replace. I don't know what the filtration is, but is should be fine for a stock motor with a carb. If you want to look at parts catalogs, you might could get a bigger filter for something using a factory 390 or a 400.

 

[Broncobowsher]

If you want to get into preferred filters, I go for the mid 80s to mid '00s GM EFI filter. Lots of capacity and good filtering as well. You can get at any auto parts store.

https://www.amazon.com/dp/B000C9SR90/?tag=cbama-20

And for connections https://www.amazon.com/dp/B000CIV4QO/?tag=cbama-20 and https://www.amazon.com/dp/B07VDB99K1/?tag=cbama-20 are some options

Don't worry about it being an EFI part. It will work great on a carb application.

 

[rockinrich]

If you have a new sock on the pickup, it will last a long time. As far as the inline filter is concerned, Is that a glass or plastic cover? A rock or some other debris hitting the bottom of the truck could break a glass cover. Why not plumb in a larger canister filter or something like Ford had on the early 90's 302? Take a look at WIX 33027. Cheap and easy to replace. I don't know what the filtration is, but is should be fine for a stock motor with a carb. If you want to look at parts catalogs, you might could get a bigger filter for something using a factory 390 or a 400.

thanks bud,it is glass, depending on the overall consensus on the filter before the pump maybe i won't even need it but if the consensus is too use it then maybe i'll try to give it some sort of protection against something breaking it and then if it still breaks i'll go with a canister type.

 

[rockinrich]

If you want to get into preferred filters, I go for the mid 80s to mid '00s GM EFI filter. Lots of capacity and good filtering as well. You can get at any auto parts store.

http://[URL]https://www.amazon.com/dp/B000C9SR90/?tag=cbama-20

[/URL]
And for connections https://www.amazon.com/dp/B000CIV4QO/?tag=cbama-20 and https://www.amazon.com/dp/B07VDB99K1/?tag=cbama-20 are some options

Don't worry about it being an EFI part. It will work great on a carb application.

Thank you,appreciate the links but if i was going to run nylon 5/16 lines i'm not sure if those would work huh?I was planning on running the nylon and then at bends use 3/8 rubber fuel line.

 

[rockinrich]

Anyone else have thoughts on if adding a filter before the fuel pump,100 micron is needed considering i'll be adding a 40 micron between the pump and carb as well as a new sock and sending unit in both tanks? Thanks!

 

[4xfun]

The Mark VII used a 5/16" nylon line. There are fitting and a canister fuel filter for that model. The fitting have a barb for the nylon line and a hooded fitting that uses a plastic clip to lock onto the filter.

 

[rockinrich]

The Mark VII used a 5/16" nylon line. There are fitting and a canister fuel filter for that model. The fitting have a barb for the nylon line and a hooded fitting that uses a plastic clip to lock onto the filter.

thank you for the info!

 

[rockinrich]

If you know you have a fresh sock on the pickup, I would skip the 100 Micron.

i'm taking your advice on skipping the 100 micron filter,thank you!