Tuesday, March 17, 2020

Custom Fuel Line for the 'Vette

I have a problem.  I have an engine from 1974, a car from 1977, an intake from 1985, a carburetor from who knows where, and I need to run a fuel line.  I've tried a few "stock" ones, but they don't quite fit.  I really want to avoid that stupid hose underneath the braided stainless that shifts, moves, and vibrates its way into rot and crack.  It has been a bit frustrating to say the least.

My brain finally had the answer - build one.  The carburetor is a dual-inlet carburetor, and the inlets are not horizontal - they angle down toward the engine.  Also, to the front of the engine is a water hose adapter to help cool some parts - I have to route around that.

Here's what I need to do :

  1. Make a trunnion to bring the three fuel lines together
  2. Bend the fuel lines into shape
  3. Solder the lines into place

Trunnion:

My biggest concern is the union of the three tubes.  I bought some stainless steel fuel line, and I bought a chunk of 7/8" stainless steel hex bar.  I sliced a piece off, about 1.25", chucked it into the lathe and faced it (and chamfered it).  Then I flipped it, drilled a 3/8" hole in about 3/4", and added a bevel for aesthetics (seriously, it was the weight, since this was going to be floating as a solid piece when I was done).



Then I took it to my mini mill, and set it into vise in a vise (tool makers vise at 90 vertical in all angles, then that tool makers vise put in the angle vise at a 45 degree angle on the flat end).  This allowed me to mill off a surface and then drill another hole into the back side at a 45 degree angle.





Once that hole was deep enough, I pulled the tool makers vise out (part still in it), and secured that to the mill table.  This allowed me to find the next hole parallel to the first one put in on the lathe.  I used a series of drill bits until I broke through, and then had to switch to an end mill.  Being the mill with the tables locked in place, it was right on, so changing the tooling didn't matter.


Now I have the trunnion.  I need to get it cleaned and degreased, but I was able to run a quick test fit.



Bend the Fuel Line 

Next up I need to bend the fuel lines.  I have three lines that merge into the trunnion.  The two feeding the carburetor need to bend toward the carburetor (one is a 90 degree bend, the other a 45 to match the angle of the trunnion), and then have a second bend in both of those to match up with the angle on the carburetor inlets (about a 60 degree bend) and to keep the line from interfering with the intake manifold.  On the other end of the fuel line, I need to bend over the front of the engine and go down to the fuel filter and pump.

First, I need to cut off a chunk of fuel line for each one of these rods.  I'm going to cut more - it's easier to have too much than not enough, and right now, I'm not quite sure where things are going to end up.  I'll cut things about two inches longer on each end than I need, then I can cut things down prior to soldering.

Soldering

I'm not using electronics solder - I doubt it will hold up to the vibration.  That leaves welding solder and jewelry solder.  Both should work (both are based on silver solder, and should have the strength I need).

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