Fuel pressure regulator/bypass question

[tommyg29]

My new Mallory 110 fuel pump is acting up and I figure I might as well install a fuel bypass to take some of the pressure off it, though Chryco you think it shouldnt be needed, but...I have the return line still mostly in place from just behind the right front wheel, back to the connection behind the rear wheel, where it has been capped off. I have several questions.
First, can anyone tell what type regulator this is, and more importantly, does it look ok to add a return line to it? assuming that is what the rear nipple is for. Also, how do I adjust the pressure with the top valve? Do I need to install a downflow pressure gauge, back off the nut, and tune it in, and tighten the nut again? Any more specific directions or advice?
Also, rather than reroute the return line to the sender on the left side of the car, can I just return the fuel back through the existing connection in the picture? Will that find its way back into the tank safely and efficiently? I think I read somewhere in here that some do it that way?
Thanks.

[ShelbyDogg]

Looks like a Holley regulator.  You have to loosen the nut then turn the adjuster while you are watching a guage either at the fule line or in place of that plug at the other end. I used to run a hose from each end to each bowl on a holley and I had a tap fitting where I could remove a plug  and install a little guage when adjusting pressure.

You can run a return line to just about any line from the tank. If you look inside a tank all of those lines just sit on the top to allow vapor to enter. Take a look with a mirror.

[ntstlgl1970]

Unless that is a bypass regulator (usually the return goes out the bottom of the regulator), running a line off the side with a plug without a restricter of some sort in that line is going to give you low/no fuel pressure.

[tommyg29]

Ok, checked the Holley website and it is a holley regulator. And yes, when using the bypass feature, the return does go out the bottom. I think I will make that a project one of the next few weekends, and I'll order an inline gauge to permamnently install just before the carburetor.
When I hook up the gauge I'll know exactly what my pressure is, and if I need to lower it down to about 5.5, will that necessitate adjusting the floats? And is an air filled gauge adequate for permanent installation?
Thanks.

[ShelbyDogg]

Ok, checked the Holley website and it is a holley regulator. And yes, when using the bypass feature, the return does go out the bottom.  if I need to lower it down to about 5.5, will that necessitate adjusting the floats? And is an air filled gauge adequate ?

Bypass feature on a regulator for a carb? Send us a link to what you're looking at. The bottom, in your pic is for the supply side from the pump.  It never hurts to check your fuel level after making any changes. It only take a minute or less.  An air guage is fine. That is all that was used before silicone gauges came out. Harbor Freight sells a neat little digital gauge for I think less that $5.

[Chryco Psycho]

pressure adjustment will require float adjustment
 Fuild filled guages are best for mounting on th eengine but a dry guage will work

[tommyg29]

This is the link:

http://www.holley.com/12-803BP.asp

Download the instructions. My setup would be figure 2A, but I will install an inline gauge right after the regulator.
Would it be ok to run 3/8 fuel hose return line back from the regulator about 18" to the end of the capped off steel line, which is just under the firewall. It would run within a few inches of the header.
Also noticed the supply line to the regulator is 3/8", but from the regulator to the carb is 5/16". Is that normal?
Thanks.

[tommyg29]

ok, I'm sorry. I'm new at this, and since I'm working with fuel I know I've gotta get it right, and safe, the first time.
So, if I sound slow...I am.
But one more time for the beginner here.
I looked closely at the 4 rubber vapor lines leading to the vapor recovery chamber up in the right side of the trunk, which I assume is a remnant that cudas use from the challenger filler pipe (and why do they need 4?) The 5th line is the return from the 3rd nipple on the valve cover breather I assume (since I dont have one).
Now what I want to do is use that unused 5/16"? steel line which goes back to the vapor chamber, but it just doesnt seem that I should be sending so much fuel back from the regulator back into that chamber, since its designed to only receive vapors. Should I just hook the end of the vapor return line to one of the 4 vapor lines for a direct return to the tank?

[ShelbyDogg]

Never ever hooked it up that way, but its worth a shot since you want to do it.  To me it looks backward because you're using the output as the input.

Run your bypass so it goes right back into the tank. 

[tommyg29]

Well, after doing more research, and for the benefit of anyone like myself who reads this knowing little about the system, I can answer several of my questions. It seems so simple once you can see a simple drawing!
First there are 4 lines to the vapor separator because each line goes to a seperate corner of the top of the tank, to insure vapors can escape no matter the angle of the car. And even though I am not using the line to the breather (i'm leaving it open in the right rear fender well, I hope this is safe) I think the best course for the return fuel from the sender is to run it right back to the fuel sending unit, 5/16" all the way, using steel as much as possible. Is 5/16" brake line ok? Its easy to bend and work with. But I dont think I have to worry too much if I have to use rubber in a few places, cause it should be under relatively low pressure.
And no, the cuda vapor separator has nothing to do with the challenger.

[ShelbyDogg]

I buy the new 3/8 sending units with the little 1/4 return line in it. I drill out the 1/4 and insert a 5/16 brake line. Inside, I bend it so my returning fuel is dumping away from my pickup filter then snug it to the original pick with 2 stainless steel hose clamps. On the outside, I bend a 90 degree turn to match the 3/8 line then braze tube to the hole.  This will leak when your tank is full if it isn't sealed up very well.

[tommyg29]

Ok, so I'll buy some 5/16 brake line, connect it with a small length of rubber hose, and run it over to the sender, but I thought my sender already had a 5/16 return (which is capped off). If not I'll figure it out. I saw somewhere on the site that mod to drill out the sender. Good idea.
Will a small handheld tube bender work ok?
Thanks.

[ShelbyDogg]

I use a small 2 handled bender and one that you just hook to the tube and bend with. In most cases you can just use your hands to bend brake line.  Use as little rubber hose that you can.