Question about fuel line size and vapor separators

[Chargered]

Wondering if anyone has some experience with this. Planning to upgrade to a 3/8 tank to fuel pump line and a higher volume fuel pump for my 1970 Charger, 440 6-pack.

I'm finally getting around to replacing my fuel sending unit that has been leaking. I ordered a new sending unit from Kramer with the 3/8 feed line and a 1/4 inch return line. I also ordered a new higher flow Carter fuel pump from Mancini with a 3/8 inlet and 3/8 outlet. The plan was to install a Vapor Separator so I could run a 1/4 return back to the tank. However, Mancini told me they don't make a Vapor Separator with a 3/8 inlet, only a 5/16 inlet. So with the vapor separator your kind of defeating the purpose of the 3/8 feed line.

So three questions:
1. If you run a 3/8 line from the tank to the pump and then reduce it to 5/16 going to the vapor separator, are you defeating the purpose of having a larger feed line and higher flow pump?
2. Do they make a vapor separator with a 3/8 inlet?
3. Should I install the vapor separator or just run without it?

 

[Sixpactogo]

From what I remember about my 440 Six Pack, I think the factory set-up used 5/16" from the separator to the Carbs. I would install it according to your plan and not worry about it. You won't be starving your engine. From my thinking, the high flow pump will send any excess fuel back to the tank anyway. The main thing that this set-up did was to stop vapor lock issues. IMO of course.

 

[69hemibeep]

5/16 is plenty for multiple carbs the 3/8 line allows for the return flow also.

 

[Chargered]

Thanks guys. I think I'll go ahead and add the vapor separator and just neck the 3/8 (coming out of the pump) down to 5/16 for the vapor separator.

 

[moparedtn]

Let us know how the new sending unit works out on gauge accuracy.
To date, I know of no reproduction sending unit that's worth two cents in that category.

 

[Chargered]

Hey guys, one more stupid question that I should probably know. When I screw in the fittings to the fuel pump (or any other fuel line fitting), do I use anything on the threads for sealant? I'm pretty sure that fuel would eat up any thread tape.

 

[Sixpactogo]

I don't think any teflon is needed. The fittings are tapered so shouldn't leak if tightened properly. Probably wouldn't hurt anything though.

 

[RJRENTON]

IMO....regarding the fuel line size....
3/8" from the tank to the pump will make it easier for the pump to draw fuel from the tank due to reduced suction pressure st the pump, but not really needed. The factory used 5/16" tubing from the tank to the pump and 1/4" tubing from the vapor seperator back to the tank. From the vapor seperator to the hard lines to the carbs, 5/16" was used becsuse the fluid is under pressure and will overcome any piping restrictions. BTW....the fitting connections at the "T" fittings and carb inlets are SAE 45° flare connections and assembled WITHOUT any teflon tape or pipe dope on the threads. Any hose connections, supply line to the pump, pump to seperator inlet, seperator outlet to carb supply hard lines are made with gasoline rated nose and "keystone" style crimp connection clamps, if origionality is wanted or needed. Just my opinion of course.
BOB RENTON

 

[Chargered]

IMO....regarding the fuel line size....
3/8" from the tank to the pump will make it easier for the pump to draw fuel from the tank due to reduced suction pressure st the pump, but not really needed. The factory used 5/16" tubing from the tank to the pump and 1/4" tubing from the vapor seperator back to the tank. From the vapor seperator to the hard lines to the carbs, 5/16" was used becsuse the fluid is under pressure and will overcome any piping restrictions. BTW....the fitting connections at the "T" fittings and carb inlets are SAE 45° flare connections and assembled WITHOUT any teflon tape or pipe dope on the threads. Any hose connections, supply line to the pump, pump to seperator inlet, seperator outlet to carb supply hard lines are made with gasoline rated nose and "keystone" style crimp connection clamps, if origionality is wanted or needed. Just my opinion of course.
BOB RENTON

Thanks Bob, I really appreciate all the support and good advice I'm getting here. Its helped greatly. Does anyone know if you need an inline fuel filter in addition to the factory style fuel vapor separator, or is the fuel separator provide enough filtration already?

 

[RJRENTON]

Again, in my opinion, adding a filter to the suction or inlet side of the the pump is redundant, in that it adds to the suction pressure the pump must overcome and may lead to pump cavitation or low delivered fuel volume under max demand conditions. The fuel vapor seperator is a filter of sorts in that it contains a screen to filter out the crud, should any be present. I'm sure others will have their own opinions and preferences. The system as discussed, is what Mopar designed and installed. This is what i have on my RS23V0A****** and it functions just fine for me.
BOB RENTON

 

[69hemibeep]

There is a fuel filter that does the same thing as a separator. All the separator has for a filter is a screen and you want the filter between the pump and carb.

 

[RJRENTON]

There is a fuel filter that does the same thing as a separator. All the separator has for a filter is a screen and you want the filter between the pump and carb.

Who makes/markets the filter you mention. The Mopar vapor/seperator functions as the filter with its internal screen, although I do not know the screen size or its micron rating. I've been using the Mopar part for years with no fuel system dirt or crud in the carbs.
BOB RENTON

 

[Moparfitter]

I like to use anti size on the threads and a little on the face. Helps in getting things tightened.

 

[RJRENTON]

I like to use anti size on the threads and a little on the face. Helps in getting things tightened.

SAE 45° flare and JIC 37° flare fittings are designed to be assembled dry WITHOUT the use of any lubricants, anti-seize compounds or pipe dope or teflon tape on the exposed threads. Its your vehicle so you can use what ever methods you prefer.
BOB RENTON

 

[Moparfitter]

SAE 45° flare and JIC 37° flare fittings are designed to be assembled dry WITHOUT the use of any lubricants, anti-seize compounds or pipe dope or teflon tape on the exposed threads. Its your vehicle so you can use what ever methods you prefer.
BOB RENTON

Most understand the threads on these type joints don't provide the sealing. Like most steel on steel thread joints lubrication doesn't hurt. I've fought these fittings on my six pack fuel lines and have found it helps. Also being a pipefitter we don't assemble much without lube, why fight friction.

 

[Lionized]

Who makes/markets the filter you mention. The Mopar vapor/seperator functions as the filter with its internal screen, although I do not know the screen size or its micron rating. I've been using the Mopar part for years with no fuel system dirt or crud in the carbs.
BOB RENTON

Fram and Wix both make return line filters.

The system I am installing this weekend will include a Fram G3606 mounted directly above the reproduction vapor separator. I'm upgrading from 5/16" feed to 3/8" feed and 1/4" return. I'm also replacing the pump with and Edelbrock 1723 so it will be 3/8" to the pump, 5/16" to the carb.

 

[440+6]

As far as filters, for mine there is the sock in the gas tank, the fuel separator with a screen, then each of the three carbs has a brass/bronze porous type filter at each inlet ( can't remember what those are actually called).
I've owned the car for over 40 years and never any sort of fuel problems.

 

[69hemibeep]

And on the right are more suggestions
https://www.summitracing.com/parts/wix-33041?rrec=true

 

[RJRENTON]

Fram and Wix both make return line filters.

The system I am installing this weekend will include a Fram G3606 mounted directly above the reproduction vapor separator. I'm upgrading from 5/16" feed to 3/8" feed and 1/4" return. I'm also replacing the pump with and Edelbrock 1723 so it will be 3/8" to the pump, 5/16" to the carb.

Out of curiosity....why would you put a filter on the return line?
BOB RENTON

 

[69hemibeep]

Out of curiosity....why would you put a filter on the return line?
BOB RENTON

He is putting the filter between the vapor separator and the carburetor