There are pros and cons to both but I like having an electrical pump to prime the float bowls after the car's sat for a while. It's also nice for checking float settings without having to run the car.

I read the 4 psi Mallory has a adjustment screw that takes it up or down about 1 psi. Don't have the FSM in front of me but I think it says about 3.3 to 4.2 psi for SU's. 3 psi might be a little low unless you drive slow. In Ztherapy video it does say fuel pressure affects mix (maybe higher pressure keeps fuel level in the bowls steadier?).

I had a fuel starvation problem when getting on it and thought it was the fuel pump but it was a combination of other things. Using modded needles and slightly higher than stock float height seems to help. My stock rebuilt mechanical pump puts out 3.5 to 4.0 psi (usually 3.9) while driving, depending on temperature, amount of gas in the tank etc. Pressure nice and steady, no vapor lock in severe conditions. No return line. Some cooling system cheats though. I have the float bowl vents going to a catch can so I'll know if they overflow. So far OK.

Don't like the new tin-hat mechanical fuel pumps though. They look crappy and they don't have screw-in fittings, so you can't adapt it to AN.

Edited March 1, 201510 yr by Stanley

I have heard (and not verified) that a return line takes care of the loud electric fuel pump noise............FWIW

how can you get rid of the return line with a mechanical pump? it would seem that there would be significantly different fuel demands a 4K freeway cruising vs. stomping on it at 4K and since the mech pump would see the same rpms the flow would be the same, so wouldn't that over-pressurize the bowls? or is there a mechanical pressure release inside the pump?

 

same question for the electric pump - without a return line, does the pump shut off when it reaches a max pressure?

 

sorry for the slightly off-topic questions, but this thread group seems to know a bit about fuel pumps - if it's an annoyance i can start a new thread...

Geoff

 I believe these mech. pumps are basically the same as the old Chevy & Ford pumps. No return line back then. Nor do I think there is a pressure relief valve. Needle & seat will cut off fuel as long as the pressure is not too high. My only experience with elec. pumps are Lucas.   If there is no clicking, you smack it with a small implement of destruction. Otherwise the clicking slows down as full pressure is reached.

 BTW, The stock fuel line set-up is coming with the SUs for the new build.

Mark

sweet - i think you and i are on the same page...

So I think I've replied to a similar topic in the past, but will summarize my experience here.

 

First I have a late manufacture 260Z so it was already equipped with an electric pump as well as mechanical.  It also had the original convoluted wiring scheme that only turned the pump on under certain conditions.  One of my goals of this mod was to be able to "prime" my Webers with the key in the on position.  I find that when the car sits for a while the Webers will get dry and the mechanical pump by itself was not sufficient to provide that prime. 

 

I did eliminate the mechanical pump entirely.  I wanted to be able to use the existing mounting at the back of the car near the tank for the new pump, and managed to find a brand new pump that was a carbon copy of the original one that came with the car.  The pump is a Facet / Purolator FEP-60SV and bolts right up to the OEM mounting points.  The pump does give off some noise / ticking which is noticeable when I'm priming the carbs and the car is not running.  I actually like this as I know for sure that the pump is running, but one my car is started, you don't hear it at all, especially over the exhaust.

 

I completely removed all of the OEM hard lines as well as the return.  I run a SS braided line directly from the pump up to the passenger side part of the firewall where it terminates into a FPR I believe made by Summit Racing.  From there I run a line from the side output of the FPR around the valve cover where it terminates into a 3 output fuel log which feed each of the 3 Webers.  It works great without a return and I've never had vapor lock problems. 

 

Hope that helps.

 

Mike.

 

 

Mike, I never get tired of looking at your engine bay

I installed an airtex right where the old mechanical pump was. Works great...no need for a fuel pressure regulator.

The best thing that happen when I switched to the RX7 pump is: the Webers would drip gas after the car was turned off with all the other pumps I tried. That has been greatly reduced with the RX7 pump. With other pumps the fuel pressure would stay up when the car was turned off. When the power goes off on the RX7 pump the fuel pressure falls immediately. Haven't had any problems with fuel supply, but I don't race, just around town use. I have pushed it a little with no problems. No regulator, pressure is good enough. On the other pumps, maybe if the return line was use so the pressure could bleed off it would have the same result but I'm not using the return line at all.