Fuel line size?

[dleedvm]

Hi everyone,
I installed my new 502 water pump finally but happened to notice that my fuel line from the shutoff valve to the in line polisher and finally to the old mechanical pump is some Delco hose with no USCG A1 designation. Also, it says it is 3/8" yet the replacement A1 rated hose here is 5/16". Is that "close enough" or was the old hose too large to begin with? Also, the electronic fuel pump just with the pressure cut-off switch just seem like more things to go wrong, especially when my mechanical pump seems to work like a charm. Is it really important that I upgrade? Thanks
David Lee
Stillwater, MN

[Ball Racing]

I use 5/16", your only feeding 30hp if you could reach max rpm, and for most it's just barely over a gallon a hour useage.
Cars with 200+hp have been feed off 5/16" line.
But some people like to go big and use 3/8"
If you keep the electric pump the law requires the cut off switch.

[joe_db]

The hose needs to match the barb size. Don't try and cram the wrong size on.

[sastanley]

Originally Posted by joe_db

The hose needs to match the barb size. Don't try and cram the wrong size on.

+1..I made this mistake and had little pieces of rubber all up in my fuel system back in the day.

[dvd]

Yeah. I'm with Joe use whatever size hose fits on the barb and be done with it.

dvd

[Dave Neptune]

I have worked on more than one A-4 with the fuel lines plumbed in 1/4" coppper tubing, that's 1/4" on the OD and around 3/16" on the inside diameter. Those engines had no fuel starvation poroblems at all.

Just be sure to use the correct hose sized fittings and no teflon .

Dave Neptune

[hanleyclifford]

I think fuel line size selection has more to do with length of run and head requirements than actual fuel delivery. As Dave said, many A4s to fine with 1/4" but the pump might like a larger line if it is working from a distance.

[campbdon]

While troubleshooting starting and running problems I noticed that while the main fuel line run was 1/4" ID there were pieces connecting the pump to inline filter to carb at 5/16". I'm guessing the PO found the larger hosing easier to connect on the barbs, but I'm wondering if going from smaller to larger might introduce some problem, like air in the line? In any case I plan to replace those segments with new 1/4".

[Dave Neptune]

No problems, just be sure the fittings and hose match size for a good seal.
Stretching a hose over a larger barb or compressing one on a smaller barb is only creating probable problems that can go BOOM.

I have seen size adaptors all over some engine fuel supply systems, this usually happens with many years of so-so work. For ease of replacing and carrying parts I do suggest that the system be the same tank to carb.

Dave Neptune