So what micron level is really necessary for the big Holley 6-valve pumps and a Holley carburetor? Basically you have a set of rubber fireplace bellows pumping fuel through a garden hose up to a coffee can with holes poked in it sitting on top of the engine, right?

Edit: Never mind - looks like that question was answered on page 2.

Bud I ran the FST Performance setup before the pump which is a 4 micron. The pump pumped fuel like a garden hose. I know this because I was adjusting the valves one time and I had to take of the hose at the fuel rail to get the valve cover off. The stingers in my boat are like a grid system (balsa) it has 12x12 square boxes about 12" deep. Hit the starter button a few times to turn the motor over and I could smell fuel (thinking to myself that's'a strange) so I thought what the heck hold the starter button and see if I can see a leak. Yeah the fuel line was disconnected laying in the stringer box which has a drain hole and a couple revolutions on the motor the box was 1/4 of the way full. At that point I realized how stupid I was but at the same time I couldn't believe how much fuel the pump would move.

OK, this looks like the plan:

1/2 inch line up to the fuel/water filter head, with a WIX 33244 filter on it - that one has a 19 micron rating and flows 12-15 GPM. 1/2 inch line from there to the Holley 6-valve pump. Probably #8 AN line up to the fuel pressure gauge, splitting off to #6 up to the carb.

Do I need some kind of filter before the fuel pressure gauge? If so, is there something that will just screw in-line at that point?

The tolerances depend on the pump, like a holley is probably not that bad and you could be ok, but something like an a1000 has tight tolerances. On an a1000 install Aeromotive says a pre filter is necessary, and wants it to be 100 micron. Obviously this is pump specific but physics are physics. If you put no filter before the pump there will be less restriction then if you put a 100 micron filter, and a 100 micron filter before the pump will have less restriction then a 20 micron filter, so on and so forth. So the question is do you want to restrict the flow to the pump? My answer is no, I want to supply my pump with as much fuel as it wants, I use what I need, and return the rest to the tank.

Something else to consider. Micron ratings do not depict flow. You can have a 10 micron filter that flows more fuel, or say less restriction, than another brand/style 100 micron filter.

I dont have engineering numbers for you Budman, but all I can tell you, is I've been running 800HP blown with twin 850's, with a -10 line from tank to 33405 filter , then to the inlet of a six valve holley pump with a -10,, and #8 up to the carbs where it splits into 3/8 hard lines. I have friends with same setup that has supported over 900hp blown.

I think you'll be just fine with that setup on your 575hp N/A single carb engine.

Thanks MT! I have an existing #6 line that went from the pump outlet up to the fuel pressure gauge / split. Was planning to step up a size here, but now wondering if that Holley pump would be able to push enough fuel through the #8 line. What do you think?

Also, should I stick an extra filter in after the pump?

I appreciate all the help!

As stated in last post, I have -8 line from pump outlet, feeding twin 850 carbs on the blower. The pump is fully capable.

I would strongly consider the filters at the carb fuel bowls, like these. Everybody likes throwing them in the trash because they think they are a restriction. As long as they are changed on a regular basis, they will move more flow than the .110 needle can.

http://allcarbs.com/detail.php?pid=7...&ctgn=61&stt=0

Budman, those little filter thingy's I am talking about....you may find local under any of these part #s, from oreillys, advance, autozone, napa, etc.

AC Delco GF455

Holley 162-500

Fram CG13

Wix 33050

Purolator F10021

Do those slip in behind the fitting in the carb inlet? Do they require a spring to hold them against the fitting like the Qjet ones do?

Thanks!


Edit: Never mind Mild, answered my own question!

http://www.summitracing.com/parts/hl...FQEcaQodix0A4Q

Hmmm, the Summit listing says that these things also fit Q-jet inlets. Logic would have it that it would go the other way as well. I have a bunch of the little screen filters from various Q-jet rebuilds. I might see if one of these would work. I would think that they would flow about as well as the metal filters.