What size fuel line?

I almost don't want to post this, it's so simple, but I can't seem to find an answer anywhere. I'm running a mostly stock, dual carb 8ba flathead. What size fuel line should I run along the frame? I'd hate to have to buy and flare everything twice...imagine how embar***ing it would be to try and get the car running and to learn there's not enough fuel flow, or too much to maintain pressure...sheesh

 

5/16" would be a safe bet

 

1/4" has worked well for me

 

5/16" is plenty big, most of the '50s and '60s V8 cars used that size fuel line along the frame.

My '64 GTO used a 5/16" line. Big enough to feed twice the horsepower that your flathead makes, the GTO 389 made 325 or 348 HP depending on carburetion options.

The same 5/16" line size was also used on the base model '64 Tempest equipped with the standard 215-inch 140 HP straight six. It wasn't until 1968 that the GTO went to a 3/8" line.

The thing is, you really can't go too big but you can go too small on fuel line size.

 

I run 5/16" line on a '55 Buick with a 401 Nailhead, ggod size cam and 2x500cfm AFBs and have never had any fuel starvation problems, even when I took it down the track several times.

 

If you do 5/16th your set for whatever engine you decide to put in in the future save for a blown BBC or a Hemi. Also to save yourself any possibility of not having enough fuel put an electric pump back by the tank and a pressure regulator on the firewall just before going into the carb(s). DONE!!!

Frank

 

The 48-52 pickups used 5/16" line and that what I replaced mine with....works great.

 

It's good question. I'm running three 97's, so from the tank thru pre filter, fuel pump, main filter to the pressure regulator 3/8 SS hard line. From the regulator it transitions from 3/8 to 5/16. Again all hard lines.

 

Same as I was thinking. The 'rear' line has no pressure ONLY volume. 3/8" your fuel pump will thank you.

 

Having a larger line will not cause pressure drop. Personally I'd put a 3/8 line in, as it'll feed most any OHV street engine.

As noted, 5/16 or even 1/4 would work fine. But 3/8 allows growth over coming years/decades without having to redo work.

Good luck!

 

I ran a 3/8 hard line to my 750 cfm holly for my 427 ci., fuel pump holds 7 1/2 lbs. pressure

 

I agree with the guys that said 3/8 as there are no negative aspects to running larger than you need. Also keep the fuel hose as short as practical, over a few inches increases the fire hazard!

 

It's harder to bend and costs slightly more. But I'd still use it.

 

I use 3/8 SS on almost all the cars we build. Easier on the pump and you don't run out of fuel.

 

Everyone, thanks for all of the tips. I'm a bit late getting back to the party but I appreciate the info, it's good to know and hopefully someone else will benefit from this thread in the future

 

i would use 3/8.if you want to make it easier to bend you can go with aluminum line.i like it better than steel because it is WAY easier to bend and you can also polish it.

 

If you use aluminum line make sure you have lots of support/clamps, it don't like vibration.

 

Steel too, you can't over support it. I have had two people bring me cars that "keep snapping" hard lines, brake lines, in one case. Jokers just kept replacing the unsupported lines. I introduced them to the miracles that are the Adel clamp, and the self-drilling, self-tapping screw.

 

I'm having a hard time finding 5/16 to 1/4 adaptors (carb takes 1/4) for a small i6. Any suggestions on where to look other than usual chain auto parts stores? I'd like to run 5/16, as was previously (adaptor broke), with no rubber between the pump and carb. Thanks

 

Local hardware stores often have a surprising selection of fittings that will work. I hate to admit it but the big box stores often have all sorts of weird stuff...that is, when they've actually re-ordered out-of-stock items, instead of letting the bin stay empty for six months or so.

 

I have the 3/8 braided fuel injection hose from the tank to the engine. Never removed it when i took off the Hilborn injection. I have a electric fuel pump at the tank.

 

We're talkin' about a daily cruiser right guys?? Run the 5/16 line... Even if somewhere down the line you decide to switch to a sbc or something more modern with a little more horsepower , the 5/16 line should be plenty enough for it. Folks have run 400 + hp engines with a 5/16's id line on the street with no fuel starvation problems..

 

Look up a hydraulics store. Most every city will have someone that repairs hoses for dump trucks and back hoes etc. They have a great selection and in my case they are out front for you to pick through.