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Discussion Starter #1
351/392 carbed, Holley Avenger 670, mechanical pump.

I've been warned to move my fuel filter from the rear (near tank) to after fuel pum on engine side. Would you help me decide by giving good reasons why. My understanding was that I'd want filtered fuel to go to pump. But on the other hand I could see I should also move it to after the pump for pressure and performance.
FYI, from filter to pump is a straigh shot with my flex lines.

Am I wrong? This is the time to fix it. What is your vote and why?


 

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The Never-Ending Builder
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Noticed that you have a mechanical fuel pump, most of the comments about the filter before the pump are associated with electric fuel pumps. Mostly due to the electrics being damaged by garbage in the fuel tank. The diaphragm mechanical pump is usually only damaged by something that tears the rubber diaphragm. So in your case, where you currently have the filter would be OK, unless the pump has a problem pulling fuel from the tank, because the filter is too restrictive. Just my .02


You might want to move your proportioning valve and the brake lines AWAY from the headers.

Hank
 

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FFCobra Craftsman
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For what it's worth as reference.Most current cars w/ in-tank pump have some type of fabric sock on the inlet and the filter is after the pump.What do you have for a tank pickup?I like the above poster's setup w/ one either side of the pump.
 

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Kouros-

No, it does not affect the pressure. I have a Holly red with the regulator mounted on the firewall. It is set for 6 lbs.

I have one from the tank to the pump to keep crap from the tank getting to the pump. I have another to catch anything that gets by that and incase the pump starts throwing out crap. This does not include the inlet filters on the carb.

Mike
 

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Discussion Starter #7
Thanks mikiec,
I'd appreciate any other advice from others too.

-Kouros
 

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Mikiec, he is using a mechanical pump as I am. A Holley Red is an electric pump.

My pickup has a mesh screen on the end of the tube in the tank, and I plan to run a filter after the pump on the pressure side, not the suction side. The question now, is finding a spot to mount the filter in the engine compartment.

Rob.
 

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You can run one like the sixties vettes did after the pump. Here is a pic of a frame off i did last year. The hard line comes up from the pump and attaches to the filter and then the other side of the filter has a nipple fitting on it so that the rubber line and run to the nipple on the carb. The filter is held in place with a chrome bracket that wraps around it.
 

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That's a clean looking frame off Chris. I did a 72' about 6 years ago. It was fun.
 

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Discussion Starter #11
But what is the reason to have it after and why is it that is not recommended before the pump. I'm asking because if I need to change it, this would be the time. appreciate it.

-Kouros
 

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Kouros, I've been told it's easier for a mechanical pump to push the fuel through the filter (eg: Pressure side) rather than suck it through.

Like Chris points out on that Vette. Seems like most 60's cars were setup this way.
 

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FFCobra Master Craftsman
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You're carbed.
You don't need a fine filter.
A small filter at the tank and at the carb is enough.
This is not EFI.
You'd be amazed at the crap that will pass through a carb.
 

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Snake is right. With fuel injection, you need an electric pump as close to the tank in a pusher configuration with gravity feed (in tank electrics accomplish the same thing). The in tank uses a sock to filter out the big stuff that could damage or seize the pump. An external electric uses a medium (100 micron or so) filter to protect the pump and a fine (10 to 40 micron) filter to protect the tiny nozzles on the fuel injectors.

Carbs with an electric pump also require the pump to be mounted near the tank with gravity feed and a filter to protect the pump (all electrics work best this way), but the filter requirements after the pump are not as stringent.

In your configuration, the filter is best after the pump to protect the carb, but as above, the filtering requirements for a carb are not as demanding. Some people use a filter before the pump also, but I don't believe this is required.

With your hose configuration, expect to find bits of rubber and other debrie in the filter after a couple hundred miles, but it will have passed right through the pump with no issues. For this reason alone, I recommend that with a manual pump and carb, you put the filter as close to the carb as possible.

To make my long story short, I would leave your current filter where it is as it will provide extra protection and you already have it installed. Get a Summit line filter and place it just before the carb (do not get the glass one, they break!). Here is my set up with fuel injection (100 micron before the pump and 10 micron after with aluminum fuel line):

 

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Husband/Father/Son
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The reasoning behind the fuel filter location with a fuel injected car and an external electric pump, you get into the electric pump haviong to pull fuel through the filter instead of pushing it through. As the filter starts to clog up, the pump has to work that much hard to pull fuel through it and could cause a premature burnout of the electric fuel pump.

In your case, with a mechanical fuel pump, I have to agree with Mark R. on this one...Leave what you have in place, and add a secondary filter inline closer to the carb (after the fuel pressure regulator if your using one). Do not forget to check the canister mounted fuel filter after about 500 miles (I suggest a change in filter element then), and the smaller inline filter around 800 miles (again, a change of filter element at that time).....By then, all 95% of all sdystem contamination (lines, fitting slag, dirt/debris in the gas tank, etc) should be caught by both filter elements......


Hope you find this helpful.

Sincerely,

Bill S.


Originally posted by Kouros:
But what is the reason to have it after and why is it that is not recommended before the pump. I'm asking because if I need to change it, this would be the time. appreciate it.

-Kouros
 

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Too Cheap to paint!
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I have an electric pump in the same location as you, and an in-line filter up front on the way into the carb.

Works fine, easy to service.
 

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I have a Carter electric for my dual quad setup, and used the Fram large canister filter before the pump to protect that, and a glass type inline before the carbs. The seconday filter is there to catch anything residual, but is even more handy for troubleshooting if the car won't start. At least you can "see" that you're getting fuel. As suggested by others, just leave the canister there, and put another small inline after your pump...

Brian
 

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Discussion Starter #18
Thank you all for the recommendation. I was worried that I had to remove the filter in the rear by the tank. So, as I aunderstand it now, I will only add an in-line filter just before the Carb (easy because I have not put in that line yet). Change the filters after some miles and we're good to go. Thanks again.

-Kouros
 
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