Testing fuel system

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MopaR&D

MopaR&D

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The new 360 Magnum I put in my '70 Duster seems to have a much bigger demand for fuel than my old worn-out 318 oddly enough... :D I think the carb bowls are running empty when I keep it floored for a while at higher RPM. Is there a way to test the fuel pump/system to make sure there isn't a flow problem? And if there is what would be the first things to check, I'm guessing fuel sender screen? New fuel filter BTW so I know it's not that...
 
Not knowing how radical your engine is, it's hard to know what it will need in the way of fuel delivery. You may have to upgrade to 3/8 or 1/2" fuel line from tank to carb. You might just need a better pump or you might have a slight restriction somewhere. I'd start with a fuel pressure and volume test and compare it to what it should have stock. I can't remember what the exact GPM rating is for a stock mechanical pump but the info should be available somewhere. I think it's about a quart in a minute or less at a normal idle. Pressure should be in the 5-7 lbs range.
 
What makes you think it's running out of fuel? What do you have for a fuel system now?
 
First step is to rig either a temporary or permanent fuel pressure gauge, second step is to look up the specs of whatever pump you are running and see if it will pump the gallons/ time that is specified.

Unless this is a 600hp monster, you don't need a 3/8 fuel line, but you DO need a clean strainer in the tank, GOOD hoses at the interconnects, and make sure the metal fuel line is not gooped/ rusted up inside
 
electric pump and regulator set at 5.5 or 6 lbs, im guessing you have a 600 - 750 cfm four barrel, a few more details would help
 
lol no 600 HP monster here, more like 300-325... Magnum heads (w/ 1.6 rockers), KB-107 pistons for 10.5:1 static comp, Lunati Voodoo 60401 cam, Air-Gap intake, Hedman shorty headers, and 625 cfm Carter carb. Fuel system is same from stock 318 2-bbl. setup (lines, pump, etc.).

I'm pretty sure it's running out of fuel because if I keep it floored for more than a few seconds at higher RPM it will suddenly bog/cut out at times; if I let off for a bit and get back on it it's fine. And aside from this issue it runs great in all other conditions. I'm willing to bet the tank pickup is getting clogged but I want to test it first before I go pulling stuff apart.
 
i can tell you now , that i would have already ditched the 625 for a holley 750 DP. and i would have already installed an electric pump regulated at 6 . i think you are just plain running out of carburetor AND fuel pressure. thats my opinion
 
73AbodEE said:
i can tell you now , that i would have already ditched the 625 for a holley 750 DP. and i would have already installed an electric pump regulated at 6 . i think you are just plain running out of carburetor AND fuel pressure. thats my opinion
Click to expand...

You're probably right but I have 2.76 gears (and 904 trans with 2600-stall converter) and do a lot of cruising so the Carter helps save gas and it's what I had from my old engine. I may try a Holley at some point and maybe upgrade the fuel pump after I make sure the lines, pickup etc. are good. But not an electric one, those drive me nuts with the noise!
 
i have mine mounted at the rear of the car by my fuel cell on the frame rail and i cant even hear it running until i get outside and to the rear of the car
 
73AbodEE said:
i can tell you now , that i would have already ditched the 625 for a holley 750 DP. and i would have already installed an electric pump regulated at 6 . i think you are just plain running out of carburetor AND fuel pressure. thats my opinion
Click to expand...

+1 on this....my 318 has a 650 on it, with a decent cam and it is just right for what i need.
 
OK good advice guys, I will keep the bigger carb in mind. I searched around for stock fuel pump specs, they are 110 GPH and 5.5-6.5 psi. Converting to minutes for the flow rate that's roughly 1.8 GPM so I just have to find a gallon jug and see how long it takes to fill up and multiply by 1.8.
 
why dont you just get a fuel pressure gauge? they are cheap and that way you know exactly what is going on. sounds like you are making this more difficult than it has to be. a stock pump is going to jump around anywhere from 3 to 6 . my system is set up like this..... fuel cell~filter~electric pump~regulator~pressure gauge~filter~carburetor. there is never any question what pressure i have and it is a solid 5.5 for my holley 650.
 
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