pre-pump fuel filters

[wwhite72]

i am looking at putting a 100micron fuel filter in-line before the mechanical pump. Seems like there's plenty of room between the tank pickup and the hardline fitting. The problem is that i believe the rubber hose is 3/8' and the only hose barb fitting i can find on Earl's is a 1/2" hose. The filter takes a 3/8" NPT on both sides. Anyone tried installing a pre-pump filter and where did you install it...what fittings did you use? fitting a 40micron between the pump and carb should be easier since i have a braided ss line installed now. Though i have -6AN fittings up there and all the Holley filters use -8AN. Not sure if there will be a problem using different diameter fittings and lines in the fuel delivery.

 

[TommyK]

i am looking at putting a 100micron fuel filter in-line before the mechanical pump. Seems like there's plenty of room between the tank pickup and the hardline fitting. The problem is that i believe the rubber hose is 3/8' and the only hose barb fitting i can find on Earl's is a 1/2" hose. The filter takes a 3/8" NPT on both sides. Anyone tried installing a pre-pump filter and where did you install it...what fittings did you use? fitting a 40micron between the pump and carb should be easier since i have a braided ss line installed now. Though i have -6AN fittings up there and all the Holley filters use -8AN. Not sure if there will be a problem using different diameter fittings and lines in the fuel delivery.

Mechanical fuel pumps are better pushers than pullers. IMO it isn't a good idea to put a filter before a mechanical pump. Any restriction before the pump can result in fuel starvation or vapor lock issues.

Even the sock on the pick up which is no where near 100 micron causes problems when it starts to get loaded up with debris.

 

[Silverback]

You don't want to restrict the inlet on a mechanical pump at all and the insides are not the that fussy. ..

 

[wwhite72]

all true TK. i'm only trying to avoid pump damage. btw now that i think about it, the lines are 5/16 from the factory which is about as small as anything on the market. i guess i would need to start with a pickup with bigger than 5/16 (our pickup's are 5/16 right?) otherwise it's a waste of time on 3/8 fuel lines and filters with bigger diameters! I know RobbMc makes bigger pickups for 69-70 cars but not for ours. surprise. I guess i am stuck with buying a new tank and pickup, cleaning the vent cap, and putting another little 'pump to carb" filter if i want to get a clean fuel delivery system. Kinda disappointing because there are tons of performance fuel systems 3/8-1/2" for a 1970, including stainless steel tanks and larger -AN pickups. If i had a stroked 429 with a Holley 950cfm i guess i'd need to put a fuel cell in the trunk if i wanted modern fuel system!

 

[marks73]

You're already screened in the tank pick up so I just go inline to the carb.

 

[matrixx]

Maybe it's time to remove my pre pump filter. I was just so scared of a piece of trash entering my new pump and carb.

 

[marks73]

Maybe it's time to remove my pre pump filter. I was just so scared of a piece of trash entering my new pump and carb.

I'm surprised it run right.

 

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100 Micron prefilter is recommended to save your electric pump. otherwise if you have mechanical just a 40 pre carb is fine. if your tank is loaded with trash you will know.

 

[matrixx]

It runs fine, I think seems to run on the rich side still. I have all new fuel system except lines. I flushed them but I'm just paranoid.

I've driven it enought that I may take it off now that I've put about 1k miles on it. Any junk should be trapped in there if there was any.

 

[72HCODE]

i have a filter before my mechanical pump, works fine has for the last 10 years. i also have a sock filter in my tank.

what you need to watch out for is all filters are directional. usually there is a little stamped arrow on the case that tells you flow direction.

lots of people install the filter the wrong way then suffer from low fuel pressure or mechanical pump starvation.