Aftermarket fuel regulator
Aftermarket fuel regulator
I'm wanting to run an aftermarket universal fuel pressure regulator. In order to make routing hoses easier i was wondering If I could take the regulator off the carb (where the feed and return attach to the carb, and just run a line with a T straight from my regulator to each fuel bowl. Then I would have the regulator return go to the tank as normal.
If thats a nikki carb it has a feed and return line. The feed goes to both bowls. The return is slightly restricted and returns via the smaller hard line to the tank. You can dead head the feed line at the carb by plugging the return but then you have to make sure the psi is correct and less than 3 psi.
OK, what's your advice to plug the line, I would end up running a return from my regulator to the tank, so in my mind without looking at any diagrams it functions the same but adjustable and future proof.
No matter how you plumb the carb, max pressure at the needles is 2.5 to 3 psi. Any higher and the carb will flood.
When I ran a Nikki on my race car, I had good luck with a Holley 12-804 regulator using a Carter 6psi electric pump (P4603HD is the current part number). I plumbed the carb both dead head (no OE return line) and with the OE return working. The 12-804 Holley regulator is not designed to use a return line. So you have to use the OE bypass on the carb. You should add a low pressure fuel gauge (0-15psi) between the carb and regulator. Get one that is liquid filled from a reputable company.
For plumbing, the supply line was a -6 (3/8") line from the tank to the carb. Later when using a bypass, I plumbed it with a -4 (1/4") line to the tank.
The return line made it a little easier to check float levels and set fuel pressure with the engine off and the pump running because the return line creates a "leak" that simulates a running engine.
When I ran a Nikki on my race car, I had good luck with a Holley 12-804 regulator using a Carter 6psi electric pump (P4603HD is the current part number). I plumbed the carb both dead head (no OE return line) and with the OE return working. The 12-804 Holley regulator is not designed to use a return line. So you have to use the OE bypass on the carb. You should add a low pressure fuel gauge (0-15psi) between the carb and regulator. Get one that is liquid filled from a reputable company.
For plumbing, the supply line was a -6 (3/8") line from the tank to the carb. Later when using a bypass, I plumbed it with a -4 (1/4") line to the tank.
The return line made it a little easier to check float levels and set fuel pressure with the engine off and the pump running because the return line creates a "leak" that simulates a running engine.
No matter how you plumb the carb, max pressure at the needles is 2.5 to 3 psi. Any higher and the carb will flood.
When I ran a Nikki on my race car, I had good luck with a Holley 12-804 regulator using a Carter 6psi electric pump (P4603HD is the current part number). I plumbed the carb both dead head (no OE return line) and with the OE return working. The 12-804 Holley regulator is not designed to use a return line. So you have to use the OE bypass on the carb. You should add a low pressure fuel gauge (0-15psi) between the carb and regulator. Get one that is liquid filled from a reputable company.
For plumbing, the supply line was a -6 (3/8") line from the tank to the carb. Later when using a bypass, I plumbed it with a -4 (1/4") line to the tank.
The return line made it a little easier to check float levels and set fuel pressure with the engine off and the pump running because the return line creates a "leak" that simulates a running engine.
When I ran a Nikki on my race car, I had good luck with a Holley 12-804 regulator using a Carter 6psi electric pump (P4603HD is the current part number). I plumbed the carb both dead head (no OE return line) and with the OE return working. The 12-804 Holley regulator is not designed to use a return line. So you have to use the OE bypass on the carb. You should add a low pressure fuel gauge (0-15psi) between the carb and regulator. Get one that is liquid filled from a reputable company.
For plumbing, the supply line was a -6 (3/8") line from the tank to the carb. Later when using a bypass, I plumbed it with a -4 (1/4") line to the tank.
The return line made it a little easier to check float levels and set fuel pressure with the engine off and the pump running because the return line creates a "leak" that simulates a running engine.
I bought a similar setup. Kinda sucks because I bought greddy braided line, but with all the AN to NPT dapters ($$$$) that would be needed im not using it untill I run fuel injection.
Trending Topics
I would advise against this "if it ain't broke, don't fix it" when it comes to the Stock Nikki Carb. I added an Edelbrock inline glass "see through" fuel filter as an extra form of filtering and being able to see if there was debris or contamination. It was not necessary per everyone's advise and also created a potential fire hazard. Adding it meant that if for some reason the glass fuel filter broke or the seals leaked; it would be spraying fuel all over the hot engine bay. The other issue was that my startup and gas delivery had a small hesitation compared to before. It's one more obstacle you are adding to the fuel delivery so while the fuel delivery difference is minimal; it is apparent.
Last edited by TopGunM2k; Apr 23, 2026 at 06:16 PM.
Thread
Thread Starter
Forum
Replies
Last Post
rxforspeed
1st Generation Specific (1979-1985)
7
Jan 10, 2008 08:27 PM
perfect_circle
1st Generation Specific (1979-1985)
12
May 9, 2006 07:57 PM






