How to tell 3/8 fuel line from 5/16? - Chevelle Tech
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post #1 of 9 (permalink) Old Jul 17th, 06, 8:57 PM Thread Starter
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How to tell 3/8 fuel line from 5/16?

I'm trying to determine if my car has a 3/8 or a 5/16 fuel line since to me they look relatively close.

What exactly do you look for? Inner diameter or outter?

It's a '71 Chevelle that came factory with a 350 2bbl if that helps any.

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post #2 of 9 (permalink) Old Jul 17th, 06, 9:03 PM
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Re: How to tell 3/8 fuel line from 5/16?

You're measuring the outer diameter. A 350 2bbl car will probably have a 5/16" fuel line. To measure for sure, take an open end wrench and try to slide the open end over the tube. This will be very close.

Dave

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post #3 of 9 (permalink) Old Jul 17th, 06, 10:06 PM
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Re: How to tell 3/8 fuel line from 5/16?

Tubing is OD (outside diameter) and Pipe is ID (inside diameter). So the easiest way to tell the size of your fuel line, which is tubing, is to use a combination wrench. Whichever one slips over snuggly is the winner.

Steve

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post #4 of 9 (permalink) Old Jul 17th, 06, 10:58 PM Thread Starter
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Re: How to tell 3/8 fuel line from 5/16?

Thanx....looks like mine is 3/8. I couldn't even get a 5/16 wrench to fit it.

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post #5 of 9 (permalink) Old Jul 18th, 06, 10:56 AM
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Re: How to tell 3/8 fuel line from 5/16?

Quote:
Originally Posted by wanarace
Tubing is OD (outside diameter) and Pipe is ID (inside diameter). So the easiest way to tell the size of your fuel line, which is tubing, is to use a combination wrench. Whichever one slips over snuggly is the winner.

Steve
Depends if you're a plumber or a refrigeration tech.
I never understood why WE plumbers call 5/8" o.d. copper 1/2" & 7/8" o.d. copper 3/4" etc while WE refrigeration techs call 5/8" o.d. 5/8" and 7/8" o.d. 7/8" etc. One old plumber said "we don't care about the outside, we are only concerned about what goes through the inside" but I think we just want to confuse people.

I understand why pipe doesn't really measure what it's called (1/2" pipe is not really 1/2" on the inside but "half inch" is "in name only")

At one time the I.D. of iron pipe did measure correctly but as years passed better materials and better methods allowed iron pipe to have a much thinner wall thickness and since all the thread dies sizes were SET, the material had to be taken from the inside.

Sorry for getting off topic, I agree an open end wrench is the quickest way to idntify the outside diameter of tubing.

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post #6 of 9 (permalink) Old Jul 18th, 06, 11:41 AM
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Re: How to tell 3/8 fuel line from 5/16?

Dean, You think plumbers have confusing dimensions. Try the woodworking business.
How wide is a 1x6.. Answer: 3/4 x 5&1/2. etc.. Overseas plywoods (Baltic birch, for making drawers) come in 5ft x 5ft sizes so you can no longer fit them into the back of the pick-up with the cap on. Then there/s the hardware mostly measured in millimeters. We have 35 MM hinges, we have all the drawer slides in metric. The list goes on.


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post #7 of 9 (permalink) Old Jul 18th, 06, 2:54 PM
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Re: How to tell 3/8 fuel line from 5/16?

My house was built in 1939. The studs in my garage are real 2 x 4 measuring 2" x 4." Kinda neat, until I wanted to hand a ladder from the rafters, and found that the rafter hangers in the hardware store are sized for modern lumber and too narrow. I had to fabribate my hangers our of bar stock.

As far as gas line goes, if I go by the OD measurement, how can I be sure the ID will fit the fitting? Can I trust the hose manufacturer to use a standard wall thickness?

Isn't hardware fun?
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post #8 of 9 (permalink) Old Jul 18th, 06, 4:38 PM
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Re: How to tell 3/8 fuel line from 5/16?

If you have access to a pair of calipers, 5/16 = .3125 & 3/8 = .375

Cheers,

Garry

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post #9 of 9 (permalink) Old Jul 18th, 06, 8:49 PM
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Re: How to tell 3/8 fuel line from 5/16?

On the same off-topic: Not too long ago, I learned that a certain gauge sheet metal can come in different thicknesses, depending on which metal it's made of. And why is 1 foot = 12 inches, 1 yard = 3 feet and 1 mile = 1760 yards, when the numerical system we all use is based on 10? Just gotta love the so-called "standard" system. Have I ever mentioned the advantages of the metric system?

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