Greetings all, seeking your advice.

Recently rebuilt a 4180 carb for my 1987 460 powered E350 RV.

The rebuilt carb works great. The vehicle has more power, smoother idle, and the secondaries work much better than before. I'm a little surprised that there was no improvement in gas mileage however, still only getting about 8 MPG, and there's still a little stumble (or flat spot) right off the line.

The biggest problem with the rebuild has been re-connecting the fuel lines leak free. At the carb there's an inlet fuel filter and that attaches to a metal fuel line that runs a short distance to a small metal can that I believe is a fuel return device.

Long story short, I've been battling fuel leaks where the inlet fuel filter attaches to the carb and also where the metal fuel line attaches to the inlet fuel filter. I thought the problem was solved when I used some white Permatex high temp thread sealer (a type of Teflon paste) but after 600 miles I'm noticing some fuel seepage where the inlet fuel filter screws into the carb. It's not much, no dripping or anything like that, just some dampness, especially when it's cold. When it's hot it looks dry but that's probably because the fuel seepage is evaporating faster than it's leaking.

I think my options are as follows:

1) Leave it alone, keep an eye on it, and hope that eventually the evaporating fuel will varnish the thing shut.
2) Take it apart and re-assemble it...again. (wasn't it Einstein that said "insanity is doing the same thing over and over expecting a different result"?) I'm a little worried about the condition of the inlet threads on the carburetor and am concerned about stripping them out.
3) Re-engineer the fuel connection as follows; remove the metal fuel line between the fuel return "can" and the carb, replace the fuel inlet filter with a style that has a nipple, and install a nipple on the fuel return can, and run a rubber fuel line between the two. The thinking here is to isolate the fuel inlet from as much vibration as possible...

Please let me know what you think. Am I missing any other options? Is there some kind of magic word I'm supposed to say when tightening everything up that will prevent it from leaking???

Your thoughts and advice are much appreciated.

 

if it was mine, i would eliminate the little filter it has there in favor of a clear plastic one - the little one that screws into the carb doesn't filter very well. in doing so, you'll get to play with the lines a little. i'm not looking at just how much space it has where, but you might be able to install this filter with 2 short pieces of rubber hose near the carb, or you might have to put it down by the frame rail where the fuel line goes to rubber for a short section.
but whatever the details on that, i would have a piece of rubber hose between the steel can thing and the carb. IIRC the inlet threads on the carb are 1/8NPT, in which case you can buy a hose barb at any hardware or auto parts store. on the can thing, it could be as simple as cutting the line going up from it with enough room to clamp a hose onto it.
obviously, you'll want to use hose made for use with fuel.

 

Had the same problem on my 86 F350. I cut the steel line that goes from the fuel return to the carb. and installed a rubber section. That cured the problem. I also removed the small filter that is in the carb inlet and replaced it with a canister filter mounted on the frame right after the fuel change over valve. Good luck
Rodger

 

If you don't have California emissions to deal with, the other option is to use a 'normal' 4160 float bowl.

These have a swiveling nipple for 5/16" rubber fuel line on the same side as the 4180.
I use a large metal fuel filter intended for a 2002 Nissan Altima.
But I have a mechanical pump, and not the vapor seperator that you do,

 

Thank you for your replies. Your time is much appreciated.

Being somewhat lazy I was really hoping everyone would vote for option #1, but I wasn't expecting it. LOL. Looks like some variant of option #3 is the way to go.

Josh, I agree with you that the inlet "filter" is really more of a screen than a filter. However, between the distributor and associated wiring, manifold vacuum tee, and jungle of vacuum hoses, real estate in that area is in short supply. No room for an external filter there.

Fortunately, as Armashby suggests, the unit already has a large, canister style fuel filer with replaceable element mounted on the frame rail.

ArdWrknTrk does the 4160 float bowl have the banjo fitting for the inlet? That sure is a nice set up but I'm afraid I wouldn't know what to do with the 4180 vent hoses and such.

After running around for parts yesterday here's what I came up with:

1) Wix fuel inlet "filter" 33019. One end screws into the carb and the other end is a hose barb. Looks ideal for the revised set up.

2) Bought a 6'' metal line with flair fittings on both ends and the guy at the store was kind enough to cut it down for me. Now I've got two choices for the fitting at the can. One a little longer and the other a little shorter. I plan on using two hose clamps for this connection since it's just a straight piece of line.

3) 5/16" fuel line and clamps.

4) Some Permatex "PermaShield" fuel resistant non-hardening gasket dressing and flange sealant to give the tiny little crush washer some extra help in making a good seal.

Hopefully this will take care of it. I'll report back once the deed is done.

 

Saturday I reworked the carb inlet fuel line as previously described (except I didn't bother with the Permatex) and 150 miles later, so far so good.