Even though I'm a 350 guy I need some help. I got a '70 GS that will be pushing 475 hp and I need to know where would be the best place to mount my electric fuel pump and filter? I have a Mallory Comp 140 pump. Also, is there anything out there to make the installation easier as far as running the lines from the tank, etc.? Thanks, Rob
Rob Electric pumps are supposed to be mounted near the tank as possible and at or below fuel level. They're not good at sucking the fuel to the front but good at pushing the fuel forward. If you have an add on sump on the back of your gas tank, I'd mount it hanging from the rear frame x member. If not, I had mine on a bracket that hung from a reinforcement beam under the floor pan in front of the gas tank.
I am at a similar stage in my project (fuel system set-up). The plan was to run a sumped tank to an A1000 pump, fuel filter and a mallory return style regulator. 10AN to the pump. 8AN return line. What would the downside be to locating the pump above tank level in the trunk? I have a firewall between the trunk and interior. Is the thought here fuel starvation? The set-up is app. 600HP ('70 GS). I've seen similar set-ups at the Nats, so now my curiosity is piqued. Thanks. John
DOWNSIDE These pumps are pushers not pullers. That is to say, they do not suck very well. Keeping it below the source allows gravity to help 'feed' the pump so it can push the fuel to the front of the car.
I had a problem with a Mallory pump on a car when the pump was mounted in front of the tank above it. The pump would periodically "run dry" and not be able to siphon gas. I replaced it with a Holley blue pump and never had the problem again. It seems that the blue pump can pull fuel better than the Mallory (at least in my experience). Like others have mentioned, if you can mount the pump inlet below your tank sump, you won't have this problem. What you will have is an ugly pump hanging below your car that everyone can see from behind. If anyone has a "stealth" solution, I'd greatly appreciate it too!
LINE SIZE? John, Could be CRS on my part, but I always thought the larger line should be the return. Anyone got imput on this? TIA, Skip
Skip, I've heard various opinions. What I heard to be "common" was that an 8AN line should be plenty for just about any horspower combo up to 1000HP (no power adders). There is a way to validate by doing the math. I just haven't gone through the numbers yet. The more recent general (no math) concensus is that an 6AN return line would be too small. I'm not planning to run it on the street, so I don't think the cooling effect (or lack therof) is going to be an issue in regards to burning out the pump. In my plan I'm running the return from the regulator rather than from the pump (like a BG400). That would be an awfully long run for 10AN. I'm thinking of getting rid of the A1000 pump and going with something like a BG just to avoid that amount of line. John
I have the A1000 pump also. They recomend putting it at level or lower than level so your not starting the pump dry. Running it dry on start up shortens the pump life drastically.
Yes, I'm running a 3/8 inch return line. I use 1/2 inch line to feed the motor. Right now, I'm just in the 500 horse range, but I'm getting ready to bolt on the ATI Procharger (D1) hopefully next week. It should put me in the 600 range at about 6 or 7 psi. I'm also useing a return style malory regulator. The pump / regulator seem to work well with the 1/2 inch main and 3/8 inch return line setup. Rich
Well.... There kindof compairable. The 1/2 inch line is between -8 and -10. (8's smaller and 10's bigger). I'm not exactly sure how the -6 compairs. I haven't had my hands on any of it to say one way or the other.
I also tried Mallory Comp 140 in front of tank and 'kinda' high. It didn't work for me, especially with the stock pickup tube. Mallory has much more volume than Holley blue and does not like any restriction on the inlet side, espescially with a prefilter. So I did the sump kit and ran a -10AN inlet into big Mallory filter that is "hardpiped" (short nipple) into the pump. Pump is half in and half out of the trunk floor. The pump is nicely tucked up out of sight, but because the inlets on the fuel filter are on the top ends of the filter, a LITTLE of the bottom is visible. Could not be helped and still keep the -10AN feed line very close to level like I wanted it. Outlet side of the pump is -8AN which immediately goes into framerail all the way to front fender-mounted regulator. Two -6AN to Holley float bowls.. Mounting the Mallory fuel pump half-in/half-out of the trunk did several things for me. It kept feed wires VERY SHORT, as trunk-mounted battery AND fuel pump relay were mounted right there!! It also kept pump/filter ALMOST completely out of site! And the feed line into the pump was kept almost perfectly level to the pump! Since you CAN see the sump, and RED/BLUE/SILVER fuel line, I wasn't to worried about the tiny little bit you could see of the bottom of the filter. I did not run a fuel return line YET, but I do think that I SHOULD be(if I ever get the SB rebuiltou: ). I also was taught to use a larger return line than feed, BUT IMHO, ANY SIZE RETURN LINE IS BETTER THAN NONE!! :spank: I prolly will run the -10 return line when its time to run my car again!:TU: Hope I was of some help to you!:grin: P.S. BTW this setup is good upto AT LEAST 600 PONIES!!:bglasses:
Close, but not exact! The dash number refers to the tubing size measured in sixteenths of an inch! IE: -8 is 8/16" of exactly 1/2". -4 (1/4"), -6 (3/8"), -10 (5/8"), -12 (3/4"), -16 (1"), -20 (1 1/4") NOW, I told you all my fuel system secrets in 5 minutes that took me YEARS TO LEARN. Now I'm going to have to kill youou: :blast: :laugh: :laugh: :laugh: :laugh: :laugh: :moonu: :beer
Return line sizing I ran a Mallory Comp 140 with a -8 feed and a -6 return last year on my 450 HP AM&P built engine. In my case. I couldn't get the fuel pressure below about 7 pounds. Mallory said it was because of the smaller return line and to switch the feed and return. :Smarty:
My fuelpressure is always right 7 or 8 PSI. Question who has used the Tri Shield Performance Fuelpump (mechanical) that bolts right up in the orginal fuelpump place in the engine. Seems to be a real good alternative for those loud and noisy electric ones, and will out last them all. Saves also on a lot of wiring.
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