question on fuel line size

[Los_Control]

Sure there must be some reason for 2 different fuel line sizes. 3/16" to the pump, 5/16" to the carb. While all of the inlets are the same 3/8" size.

I am tempted to run the fuel line all one size, but curious why it would be wrong.

I want to replace all the fuel lines and add in the filter. I can hard plumb the filter to the carb with a bushing and a coupler, Then what size from filter to pump?

Wondering if I would be better off to fabricate a bracket and mount the filter elsewhere? Or does it work ok, direct to the carb? Just thinking of weight and stress on the carb body.

 

Edited October 22, 2016 by Los_Control

[Jeff Balazs]

Should be 5/16" on those steel lines.

Jeff

[Los_Control]

5/16" from fuel pump to carb, and 3/16" from tank to fuel pump is what I have.

I will need enough to do 2 trucks before am finished, was kinda thinking just switch it all to 1/4", buy a roll of it.

Seems like it might be easier to just have one size. But trying to figure out why OEM made it 2 different sizes to begin with, and if I should stay with what they did.

[Dodgeb4ya]

Do it right and use 5/16" fuel line all the way from the tank to carb. It was built that way....there will be.no flow restriction... it's not a Volkswagen Beetle hat uses 1/4 line!

 

[Los_Control]

Let me see if I understand this correctly. you all are saying that my old farm truck "molly" , had a farmer mechanic that put on inferior parts?

Maybe you can understand why I was scratching my head, wondering why it had 2 different size fuel lines, and not wanting to put it back together like that.

Thanks to all again, I will go with 5/16 all the way.

[DJ194950]

Think of it this way-

Your truck fuel pump needs to Suck it out the tank to pump and then push it up to the carb. Same diaphragm, just different valves to control flow direction.

If you were to get a soda and  used  a very small diameter straw, you would have to suck harder to get the same amount of soda in your mouth instead of a larger straw even if longer  it would seem easier.

Too much restriction on the input side of the fuel pump will restrict flow and be hard on the diaphragm. Add in a filter or two =more restrictions to flow.

Hope I made some sense with this.

Using larger fuel line will cost a couple more bucks and maybe a few  new fittings but will the fuel pump diaphragm last longer if nothing else.

DJ

[Dodgeb4ya]

Why would a farmer install the wrong parts on an old truck

A lick and a promise... the farmers way.

[Los_Control]

Yeah I was way overthinking it. Thinking a electric  pump pushes and a manual pump pulls.

Maybe the engineers had it all down to the CI" of the ID to get the maximum flow rate.  *face palm*

DJ194950 explained it in such a way, that even I can understand it.

All it is, some farmer before me grabbed and used what he had laying around. The registration I got out of the glove box has it registered as a farm vehicle.

Been finding a few hokey repairs on this truck so far, another example is it is a B1C. Has B1B drums in the front and B1C in the rear, need 2 spares.

This would have been done in the 70's, The correct drums would have been easily available at napa.

[Dave72dt]

I'd be more willing to  bet someone swapped out the entire front axle than go to the trouble of swapping out brakes and drums.  They would have been more common on scrapyards back in the 70's and b's would have been more plentiful than C's as well.

[Jeff Balazs]

If you consider that these trucks are over 60 years old it really isn't surprising that some have been altered somewhat from stock. God only knows what some PO did.

Jeff

[Jerry Roberts]

And most of us do our own alterations as we like .