Hello guys, new to the forum so forgive me if I’m posting in the wrong category but I didn’t see a particular fuel system board.

I have my beloved 84 Firebird that has a 383 stroker swap. I’m having a problem with fuel pressure fluctuating and intermittent flooding associated with that in my freshly rebuilt Holley carb.
I’m planning to install a fuel pressure regulator to help rectify the situation and add the extra tune ability to my setup.

My questions are: I have a dual line mechanical fuel pump. An inlet line and a return line. Can I just install a deadhead fuel pressure regulator or do I actually need a bypass pressure regulator?
If a bypass regulator is required do I just plug the return port on the mechanical fuel pump?
I’m really not grasping the need to have a bypass regulator if it’s just an additional piece in the line of flow… plus I have a nice deadhead on hand, hahaha

Any help or suggestions are greatly appreciated!

Thanks in advance fellas

 

What's your current fuel system arrangement? OEM lines from the tank to a mechanical pump?
From your description it appears that you've a supply to the pump from the tank and an outlet to the carburetor. Correct?
If that's the case then yes, you can install a "dead head" regulator between the pump and carb.

 

Yes, correct. I have the oem lines that feed up and around the passenger side from the tank. Thanks for the help skinny! I started to question myself before getting in deep with the AN fittings and lines.

 

I made it simple for myself and installed the regulator on the frame rail near the mechanical pump.
Routing then was from the tank to the pump (OEM), pump to regulator and then to an inline filter. From there to the dual feed carb rail.
I've also added a fuel pressure gauge that's fitted to a 1/8" NPT port on the fuel rail.

 

Nice, I think I’ll try to replicate your scenario. Did you notice much improvement after installing the reg?

 

Mine was a little complicated. It started with a vapour lock issue I was having on track days. Dead heading the pump wasn't allowing any fuel circulation and I found that waiting in the lanes (or in traffic ) on a hot day would cause a fuel starvation problem around mid-track.
I didn't have a regulator or a means of returning fuel to the tank at that time. My solution (after trying a return style mechanical pump) was to use a carb specific return style regulator mounted on the frame rail as mentioned earlier.
My Camaro was formerly an EFI system so there was a return line albeit too small for my new application. Ultimately I ran a -6AN line from the front to the return fitting on the tank.
Problem solved. I keep the fuel pressure around 5 PSI.
I also went with an external electric pump as there were other issues with the previous engine and the cam pump lobe and pushrod. Long story but I had the regulator in play long before that problem cropped up.

 

Man thanks a lot for taking the time to explain your situation! It’s extremely valuable to hear from others and soak in their experience and solutions. Take care!

 

That doesn't make any sense. By that description there's no output line carrying fuel to the carb. There should be an inlet line and an output line, and then maybe or maybe not, a return line.

If it only has 2 lines then ... most likely it has the inlet and output (duh), butt no return. Which is an almost surefire guaranteed recipe for problems. (ahem: opportunities for solutions)

Yes it's very possible that you'd benefit from adding a FPR. It should be a 3-port one, again, with input and output lines, plus a return; NOT a "dead head" type. Not sure why people still haven't figured out how useless those are (and pumps w no return as well, for that matter) after all these years of FAIL. Anything that doesn't have a return can only regulate by way of blocking the output until the pressure falls below the set point, then letting enough through for the pressure to rise. Obviously if the "blockage" isn't absolutely perfect, and the engine's fuel consumption is less than the leakage, the pressure can still get out of control. And, the fuel near the engine ends up just sitting there, getting heated up, which causes all manner of problems.

One with a return works by constantly allowing excess fuel to go back to the tank in addition to the above. MUCH MUCH better logic. And further, that allows cool (or at least not as hot) fuel from the tank, to be circulating all the time. ALTOGETHER a better setup.

The stock return line is 5/16". As skinny alluded to, that can be too small to allow enough fuel to return to keep the pressure under control, if a large enough pump is used. Which is why he added the -6 return line, which is 3/8" more or less; doesn't sound like that much difference, butt it's about 50% more cross-sectional area i.e. flow. Not likely to be necessary with a mech pump butt something to keep in mind in case the pressure still isn't properly managed.

 

Using the 5/16ths factory return created all sorts unstable pressure nonsense. I can't even begin to describe it other than pressure was there at cruise, somewhere else at WOT and another place altogether when idling.
The -6 evened the pressure across the board. I'm kind of surprised how well the old and ancient Holley Blue (with it's supposedly 14 PSI internal regulator) has performed. One thing for sure, I ALWAYS know when it's running.

I do need a serious rework of all the lines though. At one time I was kind of obsessed with bending up my own steel tubes. At some points (such as right at the pump which is in the original EFI fuel filter location) it's makes a bazillion twists and turns. That can't be doing much for fuel flow. I'll go with braided lines and large radius 90°'s next time. I'll also get the opportunity to put some head shield wrap over them as at one point, they run within an inch, parallel to the header.
I'll also move the regulator to the drivers side frame rail and save myself the extra length and hassle of going across the k-member. With no mechanical pump, there's no reason (that I can see) why I can't feed the carburetor from the left side rather than the right.