1969 250 i6 soft fuel line size

[Luke87gt]

Hi all, I’m going to replace the soft rubber fuel line that runs between the tank hard-lines and the fuel pump on my 1969 250 i6. There is a stretch of soft line that’s maybe 18inches long - really old and brittle on my truck.

Before I order, I just wanted to confirm what was the oem softline size? Can anyone confirm?

Thanks

Luke

[LockDoc]

Originally Posted by Luke87gt

Hi all, I’m going to replace the soft rubber fuel line that runs between the tank hard-lines and the fuel pump on my 1969 250 i6. There is a stretch of soft line that’s maybe 18inches long - really old and brittle on my truck.

Before I order, I just wanted to confirm what was the oem softline size? Can anyone confirm?

Thanks

Luke

I6 is 5/16" ID. Small block and big block are 3/8" ID. Any auto parts store should have it.
.

[Luke87gt]

Thank you for the confirmation! I thought it was 5/16”

So you’re saying that even i6 and v8 hardliners have different diameter?

Gas tanks are identical however?

I’m asking because at some point I may want to do a v8 swap.

[oneshotkyle]

Originally Posted by Luke87gt

Thank you for the confirmation! I thought it was 5/16”

So you’re saying that even i6 and v8 hardliners have different diameter?

Gas tanks are identical however?

I’m asking because at some point I may want to do a v8 swap.

Inline 6 gas 5/16 diameter hard lines as well as a specific 5/16 flared fitting at the sending unit

All v8’s have 3/8 sending unit to carb

[pjmoreland]

I believe V8s with a two-barrel carb also had 5/16 line. That's how my '68 was.

[Luke87gt]

That’s helpful

How much power will a 3/8” line support before it becomes a bottleneck?

[Steeveedee]

Smart money would be to buy the sender with the 3/8" line if you are replacing it, and use an adapter to reduce the line the rest of the way. No point in buying things twice, and an adapter is cheap. FWIW, I put a 4 barrel carb on my '64 Malibu with a 283 and a powerglide trans. Same 5/16" fuel line got me to 120 MPH. How fast and quick do you want to go?

[MikeB]

Originally Posted by pjmoreland

I believe V8s with a two-barrel carb also had 5/16 line. That's how my '68 was.

That's true. My 69 still has the OE 5/16" line that came with its 307. It was enough to support a 383 revving briefly to >5,500 RPM, and maintaining 2,300-2,500 RPM on freeways.

However, GM must have had a good reason to use 3/8" line on 4bbl engines, because they typically reduce costs wherever they can.

[Luke87gt]

Any issue to run the 5/16” lines with a bone stock 350?

[1970cstblazer]

Not with a stock 350, as the others that have chimed in have done a lot with that size line. If you replace the sending unit and hard lines for any reason, I'd recommend an upgrade to the 3/8".

[72c20customcamper]

My 68 anniversary 327 4bbl has 5/16 fuel lines hard and soft . My 72 350 4bbl has 3/8

[MikeB]

Originally Posted by 72c20customcamper

My 68 anniversary 327 4bbl has 5/16 fuel lines hard and soft . My 72 350 4bbl has 3/8

That's a cool stable of cars and trucks you have there!