OM617 into '51 Willys wagon 2WD - Page 2 - PeachParts Mercedes-Benz Forum

moon161 · #16 04-18-2017, 09:38 AM

Quote:

Originally Posted by barry12345

Technically I agree you could tee in before the fuel pressure is elevated. The only thing I was not estatic about. If air accumulated or entered in the return system you would pull this easier than fuel as the lift pump suction develops.

The fuel tank in your new car is at a lower elevation than what the same system had before. Just in general it may be workable. You will have to maintain a tight return system. Otherwise any air entering it may give you issues.

So I vote for simple and run it back to the tank. In the newer tank set up the lift pump with no fuel may have a tougher time drawing fuel initially.

In the original setup the fuel is basically almost gravity fed to the lift pump. Adding complexity or even just the possibility of issues occurring down the road. Just in my opinion is not worth it. You might never have a problem. Yet have still increased the odds of having one.

In the day when people where burning waste vegetable oil and had all forms of modified fuel plumbing. Air getting into the system was a real on going periodic issue with many of them.

Also I know of no manufactuer that did not return to the tank. They could have saved money if they were comforatable with what you propose so they have looked at it and rejected it. Even before the fuel tanks had electric pumps. Many cars had fuel return systems remember. They were always on the lookout to reduce build costs if the trade off was valid.

I agree here, and see your point. Using a T'd fuel line will accumulate air in by sucking it past fittings, this is often how people running on VO would determine that it was time to switch the VO filter when running with this configuration. The remedy here is purging the fuel system like you're done and switching back to diesel. With the design I ran, this backfed diesel down the VO supply line, along with any bubbles. If this is with the only fuel system, I see the problem here. With older gasoline systems, the carb bowl probably acted as a vent for any bubbles, IDK if or how common rail systems/hi pressure common rail systems vent bubbles.

I found making hard fuel lines completely less fun that I imagined. I ended up using 3/16 rubber fuel line, and zip tying it to the existing (leaky) hard lines for support. While this is not a concours setup, it worked well enough.

mach4 · #17 04-18-2017, 10:52 AM

Quote:

Originally Posted by stevee

can the fuel return line be T'ed into the fuel supply line? Willys tank does not have fuel return line.

There is one method that works and that is to build a secondary tank comprised of a Holley carburetor float bowl. Here's a block diagram.

You need a couple things - a boost pump to supply fuel to the unit (low pressure) and a float bowl (which is a separate unit on the 4bbl carbs). The float bowls can be mounted to a flat plate of aluminum. It also handles the air problem referenced above as the float bowl is vented.

It works great - I used one on an old Perkins swap years ago.

Note: this diagram shows a fuel flow sensor which is unnecessary. I designed this in contemplation of adding a mpg function to my engine monitor system. This design allows only one sensor to be used rather that the two sensors and a differential calculation with an intact return line.

barry12345 · #18 04-18-2017, 11:18 AM

There are probably several useful and easy to use products out there today to use as fuel lines. Do not weld a fitting into the tank or neck. Back then tanks where made of pre coated steel. Most used a much heavier coating of basically lead than they do today.

Tern steel was the name for it. I would just drill a small hole and silver solder a tube in as a return. I suspect if you welded or brazed a tube into the tank or neck the weld may be contaminated and weak. Also the fumes may be bad for you.

To support the little tube I would put a ninety degree bend in it and also solder along the part of the tube that lays on the tank then. This makes for a trouble free strong adaption. Actually if you incorporate the bend soft solder is strong enough.

Out of curiosity are you staying with the 5.3 ratio rear end?

stevee · #19 04-19-2017, 12:33 PM

We will dealing w/ the diff a bit later. The rear diff on the donor MB was 3.46 and 14" wheels. We now have 15" wheels/tires. Will need some help w/ that update. If its possible to change out ring and pinion, that would be great. But, hear conflicting info re: if we can get it down to 3.73 or 3.92.

Simpler=Better · #20 04-19-2017, 01:02 PM

Quote:

Originally Posted by stevee

We will dealing w/ the diff a bit later. The rear diff on the donor MB was 3.46 and 14" wheels. We now have 15" wheels/tires. Will need some help w/ that update. If its possible to change out ring and pinion, that would be great. But, hear conflicting info re: if we can get it down to 3.73 or 3.92.

The ford 8.8 can be found in exploders, crown vics, and some rangers with disc brakes, 4.11 gearing, and LSD carriers. 5.10 gears are available aftermarket.

I'd just swap in an 8.8 if you're worried.

Mxfrank · #21 04-19-2017, 07:35 PM

If you still have the donor car, you could probably use the entire third member. The Mercedes IRS mounts on a separate subframe. You need to weld in four mounts for the subframe, and then figure out how to tie in the shocks and spring perches. Spring and shock rates would take some thought.

Another option would be the old standby: a Jaguar axle. They use Dana 44 gearing, so the choices are wide open. Jags can be set up with standard coil over springs and adjustable shocks, so it would be a little easier to set up. Since the axle would be completely self contained, there's no problem with body mounting the shocks and springs. All you'd need to do is weld in four frame mounts and two supports for the trailing arms.