I had a RB Holley set up previously. I used a return style Holley regulator with a Holley fuel pump. Now that I have went back to the stock Nikki, the regulator and fuel pressure is an issue .I would like to keep the Holley fuel pump and regulator installed because they are almost new. The money and time has been spent.

My question is, in what configuration should I set the fuel system?

things I am unsure about:

Can I use the regulator as intended and cap off the return line on the Nikki? Leaving the regulator the exact same way I had on the Holley set up.

Can a Holley return regulator be used just as a deadhead regulator? By this I mean using a brass plug to block off the return port.

 

provided the regulator will reduce the pressure low enough for the nikki, i can't see any reason u can't run what u have. the original fuel system was return style as well.

 

Found a deadhead style Holley regulator in my stash pile. Swapped out the return style. No need to make things complicated for no reason...

I am curious though, could you run the stock Nikki carb with the return blocked off on the carb?
reason being, I converted back to the Nicki to eventually convert it for blow through turbo. Meaning I will need to use a one-to-one rising rate regulator. Which all of the ones I have seen are return Style.

 

The stock return on the Nikki serves the same purpose as the return on a fuel pressure regulator. It allows fuel to flow continuously, and provides pressure regulation via an orifice in the return line. If you have a return-style fuel pressure regulator, there should be no need to have the return line on the carb.

Others have said that they have had problems if they have a non-return style FPR and cap off the stock return line (dead-heading the carb), but I haven't tried it.

 

I agree, if you have an aftermarket pump/regulator (return or non-return) all the Nikki cares about is very low fuel pressure (2.5PSI or so?).

A non return regulator may keep the carb happy but may not keep you fuel pump happy. I have read that dead heading a lot of the pumps will cause reliability problems.

I had a bit of learning with my 1982 GS when I installed an aftermarket pump/regulator/carb. Basically, the OEM return line on the 12A cars is too small in diameter to allow a return style regulator to achieve under 3-4 PSI with an aftermarket pump.
https://www.rx7club.com/1st-generati...ation-1116260/

You probably did not experience this with your Holley because it wants a much higher fuel pressure and hence your return line size did not come into play! I am worried if you try and drop in a Nikki and dial down the fuel pressure you will never get it low enough to keep it happy (Like I found with my Dellorto which wants ~3PSI like a Nikki)

You could test this right now... turn on your fuel pump and see if you can adjust your regulator to a realistic Nikki fuel pressure. Don't quote me, but I think it is 2.5 or 3PSI. If you can't, your return line is too small for your pump to keep a Nikki happy.

Also I just realized now you followed me on IG today...!

If you see my thread, I had to install a larger diameter return line which was a but of a pain, especially to drop the tank and have a shop braze in a larger return fitting. Or get a GSL-SE tank.

 

Deleted. Wrong thread.

 

Holley FPR lowest setting is 4.5 or 5 psi I think. Only one I know of that would work on a Nikki is a aeromotive regulator made for low psi Weber carbs. I had one for a mikuni phh 44. No return on the regulator. u can still use Nikki return. Worked great. no fuel creep at idle. Very good fpr but pricey. $180+. Had several fpr before the aeromotive that were a waste of money.. Holley included.

 

Holley and Jegs and Summit (all the same regulator I think) make a 1-4 psi regulator which is ideal for a nikki. Dead heading the nikki will work but as stated it may make your pump unhappy or wear sooner.