how to plumb a fuel pressure regulator? [Archive] - Chevy Nova Forum

: how to plumb a fuel pressure regulator?


434ChevyII
31st-December-2011, 01:21 AM
I'm trying to plan my fuel system, and have a question. I've always seen (and was planning on routing) the fuel pressure regulator BEFORE the carb.
I just recently watched an episode on 2 guys garage, and there's an article in the jan 2012 car craft, where the regulator is routed after the carb. :confused:
I guess what confuses me is, wont the regulator (installed after carb) allow more pressure to build up and flood or unseat the carb?

so which is best and why?

-- I'm planning on running a return line btw.

the FLYER
31st-December-2011, 01:28 AM
i don't know everything, but this has been a reference text for me

http://www.centuryperformance.com/fuelish-tendencies-understanding-fuel-pressure-and-volume-spg-140.html

Tubbed63
31st-December-2011, 01:28 AM
I'm trying to plan my fuel system, and have a question. I've always seen (and was planning on routing) the fuel pressure regulator BEFORE the carb.
I just recently watched an episode on 2 guys garage, and there's an article in the jan 2012 car craft, where the regulator is routed after the carb. :confused:
I guess what confuses me is, wont the regulator (installed after carb) allow more pressure to build up and flood or unseat the carb?

so which is best and why?

-- I'm planning on running a return line btw.

After the carb? New one on me. The regulator needs to regulate the pressure so I am not comprehending why it would be after the carb. Should go tank to filter to pump to regulator to carb..

TorqueMonster
31st-December-2011, 01:37 AM
Never heard of mounting after the carb. Seems pointless to mount it that way to me :confused:

Holley recommends you mount the regulator between the fuel pump and the carb. Also they say to mount it as close to the carb as possible. Check out their web site they have a lot of diagrams for dif fuel systems.

Hope this helps :D

Vin63
31st-December-2011, 08:57 AM
It depends on the type of regulator that you use. Many of the diaphram-type regulators are located on a fuel log or rail and regulate pressure via a return, which typically positions it post carb or injectors. I ran a similar set up many years ago...here's a photo:

http://i268.photobucket.com/albums/jj33/vin63/1963%20C-10%20Build%20Up/Serpentine_Drive4.jpg

Here is my poppet-type pressure regulator configuration for the new engine and nitrous, which are mounted ahead of the carburetor:

http://i268.photobucket.com/albums/jj33/vin63/1963%20C-10%20Build%20Up/PE_BypassRegulators2.jpg

65 Post
31st-December-2011, 09:04 AM
I've got a Mallory fuel log that has a flow through system in it and the regulator is at the rear of the log for sale. http://www.jegs.com/i/Mallory/650/4302M/10002/-1 Just because the regulator is after the carb, doesn't mean it won't regulate. You still have the gauge in the line by the carb and just adjust it the same way as before the carb. Now, the return doesn't have to go back to the tank, you could plumb it righr back into the inlet side of the pump. A lot of racers have the regulator after the carb. It still bypasses the extra fuel and keeps the correct pressure. Dave

The Big Al
31st-December-2011, 10:52 AM
I'm trying to plan my fuel system, and have a question. I've always seen (and was planning on routing) the fuel pressure regulator BEFORE the carb.
I just recently watched an episode on 2 guys garage, and there's an article in the jan 2012 car craft, where the regulator is routed after the carb. :confused:
I guess what confuses me is, wont the regulator (installed after carb) allow more pressure to build up and flood or unseat the carb?

so which is best and why?

-- I'm planning on running a return line btw.


Ok, there are 2 types of systems, deadhead & return.

Common deadhead.

pump - regulator- carb.

Return system.

IE: if regulator is set to 6psi, everything between the pump and regulator is at 6psi.

Pump- carb- regulator - return

http://img844.imageshack.us/img844/1856/fuelpumploopsystemwithc.jpg (http://imageshack.us/photo/my-images/844/fuelpumploopsystemwithc.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)


Al

The Big Al
31st-December-2011, 10:54 AM
This is a dead head // loop system.

http://img220.imageshack.us/img220/282/fuelpumploopdeadheadcar.jpg (http://imageshack.us/photo/my-images/220/fuelpumploopdeadheadcar.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

434ChevyII
31st-December-2011, 06:02 PM
i don't know everything, but this has been a reference text for me

http://www.centuryperformance.com/fuelish-tendencies-understanding-fuel-pressure-and-volume-spg-140.html

thats some great info! thanks.

-- the info/chart that I was refering to from the magazine is from HOLLEY!
http://holley.com/data/Products/Technical/199R10569.pdf

I just don't understand, that if (for example) your fuel pump is rated at 45psi, and your carb is the first thing the fuel reaches, how the pressure regulator being mounted after the carb will work. fluid travels in the path of least resistance, so all of the pressure (45psi) will be traveling into and past the carb and building up at the regulator...thus creating fuel pressure problems at the carb...

BUT.... if you guys say it works the same, then which way is BEST???

The Big Al
31st-December-2011, 06:16 PM
I just don't understand, that if (for example) your fuel pump is rated at 45psi, and your carb is the first thing the fuel reaches, how the pressure regulator being mounted after the carb will work. fluid travels in the path of least resistance, so all of the pressure (45psi) will be traveling into and past the carb and building up at the regulator...thus creating fuel pressure problems at the carb...

BUT.... if you guys say it works the same, then which way is BEST???


WITH A RETURN REGULATOR
The pressure is regulated to what the regulator is set at.
Everything between the pump and regulator is at (setting) excess is released and returned. If regulator is set at 6psi nothing in the system is above that setting.


AL

Vin63
31st-December-2011, 07:30 PM
thats some great info! thanks.

-- the info/chart that I was refering to from the magazine is from HOLLEY!
http://holley.com/data/Products/Technical/199R10569.pdf

I just don't understand, that if (for example) your fuel pump is rated at 45psi, and your carb is the first thing the fuel reaches, how the pressure regulator being mounted after the carb will work. fluid travels in the path of least resistance, so all of the pressure (45psi) will be traveling into and past the carb and building up at the regulator...thus creating fuel pressure problems at the carb...

BUT.... if you guys say it works the same, then which way is BEST???

As Al noted, the return bypass regulator on the post side of a fuel log/rail maintains fuel pressure as a function of the return (which is one of the reasons why it's important to have a relatively large return line on high pressure pump applications), maintaining open flow to the pressure set at the regulator - this is how I ran my system in the first photo. Keep in mind that pressure can only be built or reached on a closed system, so if the system is open and flowing pressure is not building - similar basis for almost all common rail fuel injection systems on modern vehicles.