I'm looking to up-size my fuel line and I'm not exactly sure what size is in there now.
Anybody know what size came on a 69 350/2bbl car? I tried meauring mine but there's too much corrosion around the outside of it to get a consistant measurement.

In 67 the 326 2 bbl used 5/16 and the 400's used 3/8

Now is that ID or OD? Because I have a new piece of 3/8" fuel tubing that measures .320 inside. I'm thinking those must be outside measurements. Just trying to confirm. I see alot of guys going with 1/2" flexible alum tubing but, dam, I didn't want a garden hose for a fuel line.

OD. Didn't one of the old time racers use a 3/4" X 10 foot fuel line to increase his fuel capacity?

Not sure about that but summit has a kit that comes with 1/2" alum tubing and some -8AN flex for the ends. I know I'll still have to upgrade sizing on the pickup and the filter and pump but this may be the way to go. Thanks for check Bob.

My 69 350 2 bbl has 3/8"

Thanks racer.
Seems like it should be enough volume. Now I'm thinking that maybe just an upgrade to the fuel pump is what I need. It would be great if I just needed more GPH. That's simple enough. I wouldn't mind having a quieter pump anyway. I really wasn't looking forward to installing a new line.

The firstgensite shows 5/16" for 67-69's and it's the ID, it's under the parts illustrations,does not mean 400's didn't have 3/8",
I had 5/16"ID on my 67, I replaced it with 3/8" ID. FYI Firebird had a 2 piece fuel line, one Front to rear and one on the cross member.
You should never measure pipe and tubing to the outside always to the inside diameter because of the many styles and thicknesses of pipes and tubing.
Sometimes tubing crushes on the end and measures smaller than it's actual size.

Yup, there seems to be the confusion because everyone just says 3/8 but never says OD or ID. If I knew I had 5/16"ID now I'd definitely replace it with some 3/8"ID. Might have to break down and pull a hose off one end and see if I can get a measurement that way. Jeez, what a PITA.
BTW. I measured a new piece of 3/8" fuel line that I bought and it measures.320ID/.375OD. So apparently even the manufacturers designate their tubing by OD.

You said it best, .320 is the new 3/8" ID, or I am just wrong about auto tubing! Think about it how small is 5/16" then.

I measure conduit all the time and it's always under a little, but never over the size I was using. even when I put it in a bender it looks smaller compaired to the shoe that bends it alot of tubing and conduit is made in CHINA now, not the USA.

I beg to differ. Just mic'ed the fuel line coming off the original sender for a 69 goat gas tank. Was about 3/8 OD (covered in crud). Then I mic'ed some new 3/8 brakeline and it was 3/8 OD. Metal tubing is measured OD, hoses measure ID.

They measure flexible fuel hose [rubber, braided steel teflon etc.] by inside diameter and fuel line [steel, aluminium, SS etc] by the outside diameter. The gauge [wall thickness] determines the id.
My 68 is 3/8 od steel line to the pump and an AN-6 [3/8 ID] braided steel hose from the pump to the carb. I run an engine driven pump that supplies all the fuel I need to run 500HP at 6000rpm. Very quiet compared to an electric pump.
Although IF I was going to replace the line I would put in a 3/8 ID flex line the whole length.

I was veiwing some other sites info, all the Firebirds came with 5/16" ID fuel line. Maybe 5/15" is what I always thought of as 3/8" OD.
Check this site: http://www.teufert.net/
Fred's Pontiac Info go to the Scanned parts pages, lots of info here too.

Don't know about that.
My 68 350 4 speed came with 3/8"

I think we're all talking about the same thing. 3/8" tubing is basically 5/16"ID/3/8"OD. The only way to upsize is to go with steel braid or hose because then you get ID measurements. I guess pipe and hose is measured ID and tubing is measured OD.
How stupid is that?

Pipe is "IPS" which is neither ID nor OD, just some random number.

Yes it doesn't make sense, what's IPS?

IPS = iron pipe size. It's a pipe sizing convention that goes way back, probably hundreds of years. Here is a chart of "Schedule 40" pipe sizes.

http://www.engineersedge.com/fluid_flow/steel-pipe-schedule-40.htm

There is also Schedule 80, 120, 160 that has thicker walls but the same OD's.

I'm an Electrician and that is why I thought all pipe and tubing is measured by ID and even though the conduit can be under a little, ever since we benn importing more from China.
Thanks for the chart, it even has the weight per foot too, nice!
IPS is new to me, never heard of it in my 35 yrs as an Electrician, I bookmarked the chart my need it someday.

In all cases I am aware, tubing is measured on the OD. Where it gets complicated is there are several wall thicknesses for each tubing size. For example for 3/8", you can have 0.020, 0.028, 0.036, 0.048, 0.065, etc. wall thicknesses. The easy way to remember this is to make a 3/8" compression fitting work, the OD is the critical dimension.

Well for me the critcal dims are the inside becuse that's what the fuel flow is regulated by. Really I could care less what the OD is. If you go and look at that web page that Ragu posted it does say "5/16ID" as the listed size of the original line.

Since I started thinking about this I have heard from a few that said they have been able to run off the original "3/8" inch lines up to, and above, 500HP without issues so it seems I need to go in a different direction. The concensus seems to be that a better pump is what is needed to insure a good pressure and flow to support the need but the line size is sufficient. It was suggested to go with a Carter elect pump. I'll begin my search for the right one. Christmas is coming.

Pipe is measured I.D. up to 12" then it's measured O.D.

So Bob, what did you do for fuel line?

Dude, that is an old post! i can't really remember what the deal was. That was way before the FI went on. I ended up using the existing 3/8" steel feed line and added a 5/16" steel return. I now wish I had installed a 3/8" return instead because I have a bit of a high pressure situation that I think may be caused by having the smaller return. But it seems to work ok as is. The Holley guy said I don't have to worry unless the pressure goes over 90psi. I currently idle at 72psi. The regulator on the FI unit is supposed to be preset at 58.5psi.

I think way back when I started that thread I was experiencing fuel starvation issues at the top of third gear and the car would fall on its face. I ended up installing the return but also plumbed in an electric pump over the mechanical one with a switch that would turn the electric on when the secondaries on the Qjet started to open. This arrangement seemed to take care of the starvation.

Yea, it's a bit on the old side alright.
I was looking for a tool to put a barb/bulb on solid 3/8" fuel line to help seal rubber tubing attached to the metal, and this old post popped up. Couldn't remember if I ever did hear what you did, so I got curious.

I used a regular flare tool to make a bubble flare on steel tubing. Works real good. Just practice on some tubing first. A couple of times and you'll get the hang of how much pressure it takes to make a nice bubble flare. Then a good clamp above it to hold the rubber on. Did it with some of my FI lines and I'm running 72psi. They're not coming off.