Fuel line question

[sstock]

Good morning,

I picked up some 3/8" aluminum fuel line to run from the tank along the frame rail to where the soft line will connect to the mechanical fuel pump on the engine. I'm wondering if it is too small, it nets out at 1/4" inside dia. I'm running a bored 283 NA with a single carb, mild cam with no electric pump, the fuel will gravity feed from the tank to the mechanical pump. I'm inclined to go with 1/2" that will net 3/8" ID, I know that will do whatever I need. Just thinking out loud here, any opinions??
Thanks in advance,
Steve

 

[EX JUNK]

Good morning,

I picked up some 3/8" aluminum fuel line to run from the tank along the frame rail to where the soft line will connect to the mechanical fuel pump on the engine. I'm wondering if it is too small, it nets out at 1/4" inside dia. I'm running a bored 283 NA with a single carb, mild cam with no electric pump, the fuel will gravity feed from the tank to the mechanical pump. I'm inclined to go with 1/2" that will net 3/8" ID, I know that will do whatever I need. Just thinking out loud here, any opinions??
Thanks in advance,
Steve

The 3/8" aluminum is what I use and so do most other guys.

Jim

 

[VegasBruce]

GM used 3/8 on most all of their carbed vehicles.

 

[Lee_in_KC]

Steve, I have the 3/8" line with -6 fittings feeding dual-quads on my 500+/- hp blown small-block 350, and have no issues with fuel starvation. I think you'll be fine with 3/8 on your set-up.

 

[409T]

Aren't the needle and seat assembly or the fuel filter the most restricting factors? What I mean is even if you hook a fire hose to the carb, only so much gas can pass through the seat, which has a much smaller hole than the inside of a -6 line, so as long as the line feeding the carb is bigger than the restriction(s) (multiple carbs) things should be fine. NO? I realize that is somewhat of an oversimplification, but with only 1 or 2 carbs there aren't too many variables.

 

[Differen T]

The 3/8 tube should be fine, especially with a gravity feed. If you want to prove this to yourself simply put some gas in the tank, the more gas the faster it will come out, disconnect the line at the fuel pump and watch how fast you can fill a clean one quart jar. As 409T suggested, the needle and seat are the most restrictive part of the system, but there are several variables other than the size of the feed line that affect the amount of fuel that enters the fuel bowl. As stated, the amount of fuel in the tank affects the rate of flow to some extent by the weight exerted on the fuel in the line. The volume and pressure created by the fuel pump affects the flow through the opening in the seat. Mechanical fuel pumps should have 5 to 7 pounds of pressure and fill a 16 oz Coke bottle in about 30 seconds.

Al

 

[sstock]

The 3/8 tube should be fine, especially with a gravity feed. If you want to prove this to yourself simply put some gas in the tank, the more gas the faster it will come out, disconnect the line at the fuel pump and watch how fast you can fill a clean one quart jar. As 409T suggested, the needle and seat are the most restrictive part of the system, but there are several variables other than the size of the feed line that affect the amount of fuel that enters the fuel bowl. As stated, the amount of fuel in the tank affects the rate of flow to some extent by the weight exerted on the fuel in the line. The volume and pressure created by the fuel pump affects the flow through the opening in the seat. Mechanical fuel pumps should have 5 to 7 pounds of pressure and fill a 16 oz Coke bottle in about 30 seconds.

Al

Thanks guys for the responses. I was thinking of running a filter in the fuel line before the pump, can any of you make a recommendation, something that will be mounted along the frame rail. I will also run bronze filters in the carb.

 

[EX JUNK]

Here is what I'm running on my car. It is a Fram unit.

Jim

 

[KAA]

Good morning,

I picked up some 3/8" aluminum fuel line to run from the tank along the frame rail to where the soft line will connect to the mechanical fuel pump on the engine. I'm wondering if it is too small, it nets out at 1/4" inside dia. I'm running a bored 283 NA with a single carb, mild cam with no electric pump, the fuel will gravity feed from the tank to the mechanical pump. I'm inclined to go with 1/2" that will net 3/8" ID, I know that will do whatever I need. Just thinking out loud here, any opinions??
Thanks in advance,
Steve

You didn't mention a flex line from the tank to the hard line. I might be wrong but you may need one there to. Just thinking. Sounds like you are moving pretty good. Any pictures?

 

[Lee_in_KC]

I have the same filter in the same place as EX JUNK. After having to change out a failed Holley Blue electric fuel pump in the field, I added a shut-off valve in the flex line from the tank to the filter.

 

[2old2fast]

Lee &
Ex Are you guys running that canister filter before or after your fuel pump? dave

 

[2old2fast]

Lee &
Ex Are you guys running that canister filter before or after your fuel pump? dave

 

[Lee_in_KC]

Mine is before the pump, as Holley recommends. I also have an in-line mesh filter right before the pressure regulator, which acts as the splitter to feed the two carbs. After the first Holley pump failed, I found bits of something black in the in-line filter. Glad it was there, as I would have had that black spooge in my carbs! Edels are notoriously sensitive to dirt in the fuel.

 

[2old2fast]

Go figure! ,when I talked to "holley-tech" they told me to put the filter after the pump,reason, pump would not be able to "pull" fuel through that type filter ????

 

[2old2fast]

Go figure! ,when I talked to "holley-tech" they told me to put the filter after the pump,reason, pump would not be able to "pull" fuel through that type filter ????

 

[Screaming Metal]

Go figure! ,when I talked to "holley-tech" they told me to put the filter after the pump,reason, pump would not be able to "pull" fuel through that type filter ????

HUH?????? Whats that Spud-Knockers name? Certain 'weak' pumps have trouble with air inside lines and all. Electrics are designed to 'push', not pull. Mechanicals shouldn't have a problem. If you add a little bit of fuel to that big honkin' filter, lets say, fill it up..... there shouldn't be a problem....
Always....I mean always......have a filter BEFORE YOUR PUMP! If not, you just voided your pumps warranty! Trash and water kill 85% of all pumps out there!

 

[EX JUNK]

Lee &
Ex Are you guys running that canister filter before or after your fuel pump? dave

I am running a mechanical pump so the filter is before the pump. I feel that I don't really need a shut off valve between the filter and the tank as my flex line draws from the top of the tank and not the bottom of the tank.

Jim

 

[Lee_in_KC]

Go figure! ,when I talked to "holley-tech" they told me to put the filter after the pump,reason, pump would not be able to "pull" fuel through that type filter ????

Read item #4 in the instructions...
Holley installation instructions

Jim, my set-up also pulls from the top of the tank, but because the pump sits so far below the tank, I get a good syphon effect. When I had to change out the pump in the field, I didn't have a valve, and as soon as I broke loose the inlet fitting on the pump the fuel gushed out. I had to break the line where it attached to the tank and let all the fuel flow out of the line between the tank and the pump onto the asphalt parking lot where I broke down. I'm sure the owner of that parking lot wasn't very happy about the stain and soft spot I left in his pavement! :whisper:

 

[EX JUNK]

Read item #4 in the instructions...
Holley installation instructions

Jim, my set-up also pulls from the top of the tank, but because the pump sits so far below the tank, I get a good syphon effect. When I had to change out the pump in the field, I didn't have a valve, and as soon as I broke loose the inlet fitting on the pump the fuel gushed out. I had to break the line where it attached to the tank and let all the fuel flow out of the line between the tank and the pump onto the asphalt parking lot where I broke down. I'm sure the owner of that parking lot wasn't very happy about the stain and soft spot I left in his pavement! :whisper:

I can understand you situation,Lee, but I can very easily turn my flex line upward as quickly as it is disconnected, thereby avoiding the siphon effect. As long as my line outlet is higher than the outlet on the tank the is no siphoning effect.

Jim

 

[2old2fast]

On that holley instruction sheet, below no. 4 after the warning , it says to use a coarse mesh type filter before the pump & a high quality filter after ,coarse mesh = low restriction. be my guess ?? dave