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Discussion Starter · #1 ·
Currently have a 502 MAG/EFI motor with a Whipple supercharger and a modified fuel delivery system engineered by the engine builder with advice from Whipple. The fuel line from the pressure relief valve goes back to the fuel filter. I have heard that the Ilmor marine engines do this. Lots of people don't think it's a good idea. I also heard about a kit that somebody makes for marine applications that allows the relief line to be routed back to the fuel filler hose. Anybody know who makes that product?
 

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I was told , point blank, by Aeromotive NOT to run return line to filter or anywhere in the supply line. ALWAYS run to tank or filler hose.

I got my parts from CP Performance. Basically, it is a 1-1/4" tube (about 6" long) with a 3/8" nipple in the side. You cut the filler hose and clamp this piece in. I think it was $47.
 

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Lastly, even though many don't seem to have an issue with it, but some do, I'd rather not have the water/fuel seperator before the electric pump.

In talking with Aeromotive and SX a bunch of years ago they like to only run a normal (non-cannister) metal coarse type filter in frt of the pump (less restrictive but still blocks bigger particles) and then a finer one after the pump just before the Fi/Carb.
Normal meaning like this in 60 or 100 micron:


In regards to larger Micron's think about the sock attached to OEM vehicle electric pumps down in the tank. They can't be that fine of a filter since they do not get plugged up and need changing like the fuel line mounted one's.

In regards to cannister type like the Merc fuel water seperator, the threaded nipple that the filter/seperator screws onto is on the suction side if the filter is plumbed before the pump as in most OE Merc set-ups. The nipples only extend down about an 1" or so into filter. Very easy to get trapped air and or bubbles in this type.

Here's what the bottom of the cannister adapter looks like with filter off. For photo purposes it is upside down for a better look. When installed the nipple will face down with the filter/seperator being under the adapter. Notice how the nipple sits high up in filter. Why is this done ? Water seperation - water is heavier than fuel and thus water will go to bottom and fuel will stay on top of the water, therefore the nipple being higher up will give more room for water collection by just drawing the fuel from the top of it.
 

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Discussion Starter · #5 ·
Thanks all. For a dual engine set up I was hoping that one line to the "T" and two lines from the relief valves feeding the one line back to the tank. Even though the pressure can be 35-50 psi I don't think the flow rate is very high and a 3/8 inch I/S dia. hose could handle the relief flow. I'm guessing a 600HP motor running around 5000RPM is using about 1.0 gallon of fuel per minute and I''m guessing that about 5% of that may get dumped through the relief valve. That is about 3-4 oz's per minute. Not sure about what happens at low RPM's like idle. If the fuel demand is low does a solid flow come out of the relief valve???
 
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