how much power can a 3/8 fuel line support. Iam loosing fuel pressure on the bottle and trying to narrow it down. The fuel pump is a holley blue, stock fuel lines, and stock tank..70 Chevelle. Never dynod but i would guess it should put down around 500-550 to the wheels on the bottle...
3/8 fuel line question
heavychevy
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how much power can a 3/8 fuel line support. Iam loosing fuel pressure on the bottle and trying to narrow it down. The fuel pump is a holley blue, stock fuel lines, and stock tank..70 Chevelle. Never dynod but i would guess it should put down around 500-550 to the wheels on the bottle...
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You might want to confirm that the line is 3/8 and not 5/16.
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thanks for the replys i'll have to check out hot rod and make sure iam right on the size of the line.
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Heavy do you run it at the track? If so which one?
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mainly redline and denton. You ever out at those?
Heavy,
I just went through the fuel line issue on my '70 SS. I had fuel delivery problems at the top of each gear(shift point 5400). Stock tank w/sump,Holley blue pump,stock 3/8"(O.D.)fuel line to Holley 750 w/reg. Over time the car slowly nosed over at 54, 52 and even at 5000 rpm
shifts!! Found 2 problems. 1.Holley blue pump shot. 2. Stock fuel line rusting on inside. Solution: New Holley pump and Earls braided #-8 from pump to fuel reg. Expensive? YES.Problem solved!! The ONLY way to find out for sure about fuel delivery is the timed 1 gallon test at the carb as recommended by Barry Grant. Worked for me. Check my sig. I don't make as much HP as you do and I had a fuel delivery problem. Good Luck!!
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I just went through the fuel line issue on my '70 SS. I had fuel delivery problems at the top of each gear(shift point 5400). Stock tank w/sump,Holley blue pump,stock 3/8"(O.D.)fuel line to Holley 750 w/reg. Over time the car slowly nosed over at 54, 52 and even at 5000 rpm
shifts!! Found 2 problems. 1.Holley blue pump shot. 2. Stock fuel line rusting on inside. Solution: New Holley pump and Earls braided #-8 from pump to fuel reg. Expensive? YES.Problem solved!! The ONLY way to find out for sure about fuel delivery is the timed 1 gallon test at the carb as recommended by Barry Grant. Worked for me. Check my sig. I don't make as much HP as you do and I had a fuel delivery problem. Good Luck!!
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cool i found the test on there site. I'll have to check it out sunday.
FYI, I am running stock 3/8" line in my Camaro and the Carter mech pump. My engine is currently leaning out and breaking up at 5 grand so I am stuck at my current best ET. I have observed my fuel pressure drop as low as 2 psi.
It's not the pump, its new.
I personally believe that (this is my current theory anyway) that the mechanical pump has more trouble sucking enough fuel through a 3/8" line than an electric pump has pushing it through the same size line.
I will be changing to a 1/2" pickup in the tank, a 140 GPH electric and 3/8" line forward to the engine compartment. the Carter ain't cuttin' it on my NA 383 in the low 11's so I know it wouldn't support N2O Tom
. . . and I am not 100% sure, but I believe that Ed is running the same type setup -- 1/2" from the tank into a Mallory 140 electric then 3/8" forward of the pump.
It's not the pump, its new.
I personally believe that (this is my current theory anyway) that the mechanical pump has more trouble sucking enough fuel through a 3/8" line than an electric pump has pushing it through the same size line.
I will be changing to a 1/2" pickup in the tank, a 140 GPH electric and 3/8" line forward to the engine compartment. the Carter ain't cuttin' it on my NA 383 in the low 11's so I know it wouldn't support N2O Tom
. . . and I am not 100% sure, but I believe that Ed is running the same type setup -- 1/2" from the tank into a Mallory 140 electric then 3/8" forward of the pump.
You are correct for two reasons
(1) the mechanical pump is a plunger style pump. Due to its cyclic operation the peak flow velocity in the fuel line is approximately four times that of a continuous flow electric pump. Resistance to flow is proportional to flow velocity and you'll reach a point where the pump can only pull so much fuel before the fuel vaporizes in the line and fuel flow stops.
(2) If you consider the weight of the fuel in the fuel line between the tank and the mechanical pump, the force due to launch acceleration alone will produce about 4 psi per 1G launch. Those with sub 1.6 second 60 foot times are probably launching between 1-1.5 G's. Under these negative pressures, the fuel will vaporize in the line and fuel will no longer flow.
Many running fast with mechanical pumps never recognize the problems caused by scenario 2 because of the large amount of fuel stored in the Holley fuel bowls.
An electric pump mounted at the tank can overcome these problems. For maximum performance, the pump must be rated for greater than 14 psi with a regulator mounted near the carburetor.
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Hey Heavy, I do run at Denton. Just ran Nostalgia drags there a week or 2 back. Let me know next time you head that way and Ill try to make it.
Heavy, If you do the test on Sunday post the results OK? I think you'll be amazed. Many racers have spent $$$$$$ replacing parts when they just didn't have enough fuel volume. An old drag racer told me long ago " it ain't pressure it's volume you need " I do believe you should have no less than 6 psi through the traps though.
Good luck!!
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Good luck!!
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