Fuel hoses:

[fussfeld]

1) Would anyone happen to know the sizes of the rubber fuel hoses going to the fuel pump from the metal hardlines? Both supply and return. This is for small block.

2) Do these hoses usually deteriorate and eventually need replacement? i've only seen one instance of one (supply line) leak.

The only reason i'm replacing mine is because i've swapped in a 4.3 v-6---which means the fuel pump is farther back and the v-8 lines won't reach it.


3) Can you recommend a good brand?

 

[firebane]

Its rubber so yes they fall apart. Also current ethanol fuels will destroy rubber unless its ethanol approved.

 

[chengny]

1) Inlet - 3/8", Outlet - 5/8" - 18 UNF - 2B (this is steel tubing), Return Line - 1/4"

2) No. Under normal circumstances - if properly installed - these hoses will last a
long time. Any failures are generally due to external conditions (like
abrasion/chafing or exposure to severe heat).

3) EATON WEATHERHEAD SAE 30R7 is a real good product. Available at Fastenal/NAPA/Grainger etc. - priced per foot.

Fastenal's prices:

3/8" H057 SAE 30R7 Fuel Line Hose ($3.03 Per Ft)

1/4" H057 SAE 30R7 Fuel Line Hose ($3.49 Per Ft)

 

[fussfeld]

1) Inlet - 3/8", Outlet - 5/8" - 18 UNF - 2B (this is steel tubing), Return Line - 1/4"

2) No. Under normal circumstances - if properly installed - these hoses will last a
long time. Any failures are generally due to external conditions (like
abrasion/chafing or exposure to severe heat).

3) EATON WEATHERHEAD SAE 30R7 is a real good product. Available at Fastenal/NAPA/Grainger etc. - priced per foot.

Fastenal's prices:

3/8" H057 SAE 30R7 Fuel Line Hose ($3.03 Per Ft)

1/4" H057 SAE 30R7 Fuel Line Hose ($3.49 Per Ft)

Thanks, though i'm little confused on the inlet/outlet thing: Does the supply hose have two different sizes on each end?

 

[chengny]

Does the supply hose have two different sizes on each end?

No it doesn't - and I'm sorry for not being clear. The different dimensions refer to the size (ID) of the 3 hoses that attach to the fuel pump.

Inlet = 3/8" hose that connects the pump's suction fitting to the steel tubing that supplies the engine with fuel from the tank

Outlet = 5/8" shaped steel tubing that connects the pump's discharge port to the carburetor inlet

Return line (if used) = 1/4" ID rubber hose that connects the pump's return fitting to the steel tubing that runs back to the gas tank


The primary purpose of the short rubber sections - that are used between the steel tubing and the fuel pump - is to act as vibration isolators. The steel tubing is rigidly fastened to the frame and the pump is rigidly mounted to the engine block. But the engine and frame are not rigidly coupled together. The engine sits on flexible rubber motor mounts (that are bolted to the frame) and so it is free to move independently of the frame - to a limited extent.

If the steel tubing were fastened directly to the pump - and since the engine and frame can move independently of each other - the stresses produced on the tubing would cause it to fail in a short period of time. The section of rubber hose isolates the vibration and relative movement of the engine from the steel tubing.

The pump outlet line is immune to these stresses because - at the other end it is attached to the carburetor. Since the carburetor is rigidly mounted to the engine - as is the pump, there is no relative motion or vibration between the two. Consequently, since there should be no stresses on this line, it can be steel. Which works out well because of it's proximity to the engine and the associated high temperatures.

 

[fussfeld]

Ok, that's more clear.

Just as a matter of interest, i actually had to go with a prefab A/N type pump to carb line because 4.3 v-6 pump-to-carb lines are difficult to find in salvage yards AND the aftermarket does not supply any AND GM discontinued that part#.

Remember that the carbed 4.3 was only available for like 2 model years---85 and 86 and has been fuel injected ever since. i think this is the last year for the 4.3 in vans.

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v-8 smallblock carb-to-pump lines can't be used on a v-6 because, as you can see, the fuel pump on a 4.3 is upside down.

 

[chengny]

That is frickin' sweet! I hate working on 350 gas pumps in a pickup.

 

[MadOgre]

That is frickin' sweet! I hate working on 350 gas pumps in a pickup.

You hate 350 pumps you should try a 6.2 diesel fuel pump change out hhaha not really its more like arrgghhhhhhhhhhhhhhhhhhh !!!!!!!!!!!!!

 

[MikeB]

Outlet = 5/8" shaped steel tubing that connects the pump's discharge port to the carburetor inlet

Commonly called an "inverted flare" (IF) fitting because it connects to a "flared" end on a hard line. A 5/8"-18 IF fitting connects to 3/8" hard line to the carb, although you can use an adapter to connect to 5/16" line.

Some aftermarket pumps have 1/4" or 3/8" NPT female ports for more versatility.