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post #1 of 5 (permalink) Old 06-24-2014, 04:13 PM Thread Starter
Join Date: Jun 2014
Location: california
Posts: 2
new to forum need help fuel supply

new here and not finding my problem and dont want to post new thread already covered.
have a 69 impala with turbofire 350. have added intake edle torquer intake mainfold and carter afb 600cfm carb. replaced old nipple on inlet for carb for a banjo fitting and pressure gauge. pressures were reading up to and pulsing over 20psi which i figured was causing my minimal flooding problem. shortly after instalation of gauge needle broke and fuel was seen in the gauge. warranteed and replace, again broken and leaking fuel onto intake manifold. replace again and added a fuel pressure regulator. operation was great for one day, smelled gas, looked under the hood and the regulator was now a sprinkler. i have purchesed a holly red electric fuel pump and regulator as well as a block off plate.
my question is has anyone mounted one of these on a 69 and where? it says 2amp draw is a relay needed? as well as the origional problem, is somthing else other than the fuel pump causing the spike in pressure? sorry so long very frustrated.
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post #2 of 5 (permalink) Old 06-24-2014, 04:51 PM
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Location: San Jose, CA
Posts: 280
First of all 20psi is way too high. It should be around 7psi. It's your fuel pump, adjust the pressure to 7 psi.
Relay is definitely needed, I use VW relay that has a safety switch off that feeds of your coil. When no signal from the engine/coil the pump is not pumping.
It's supposed to be mounted near the tank, as these pumps do better pushing fuel than pulling. I usually mount mine between the bumper and the tank, not sure about 68.
Also why need for the electric fuel pump?
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post #3 of 5 (permalink) Old 06-24-2014, 05:42 PM
Join Date: Jan 2006
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Welcome to the Team Thomas!

A mechanical fuel pump uses the spring inside of it to pressurize the fuel. It outputs a constant 5.5 psi on every stroke of the pump.

Big Dave
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post #4 of 5 (permalink) Old 06-24-2014, 06:21 PM Thread Starter
Join Date: Jun 2014
Location: california
Posts: 2
Thank you for the reply and the welcome. Have read that it should be 5-7 out of the mechanical. Reason for the electric is the more I have read about replacements is that they are prone to fauilure. Just want to get it dealt with and done. Now for the power source, which side of the fuse block should I pull ignition hot from if I am running inline fuse? Thank for the help
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post #5 of 5 (permalink) Old 06-25-2014, 03:35 PM
Join Date: Jan 2006
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I stopped using mechanical gas pumps because they are limited in the volume that they can move (not enough to feed much above 430 horsepower) and the fact that they heat the fuel coming in from the tank.

You could look at the heating of your fuel supply from the other direction and say that the gas you are about to burn is cooling your engine oil, but I have finned air to oil coolers for that purpose. Heated fuel expands and is not as dense as it could be, which affects how it is metered in the carb.

I like an electric pump because if I have a leaky carb (I don't now but I have had old Rochester QuadraJets that used to leak fuel out of the fuel bowl), I don't have to crank the engine over like a wind up toy to get enough fuel in the bowls to crank it up. Turn on the key and before I hit start the fuel pressure gauge is usually standing straight up at 6 psi.

Some prefer the looks of the original car; while I prefer it look unassuming and reasonably stock from the outside (you never raise the stock flat hood), but to run like a squalled dog when you find someone to race.

Big Dave
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