fuel pressure regulator for su carbs

[shadesh]

I am converting from EFI to dual SU's in my 1975 280Z. I will use the fuel tank and the metal fuel lines that are in my '75. I was thinking of using the stock EFI fuel pump, which is at 36psi. I saw a 3 port fuel pressure regulator (Mallory 4309 High Performance Universal Fuel Pressure Regulator) and was wondering if I could use this with the EFI fuel pump.? Or is the EFI fuel pump too much for this type of fuel pressure regulator.? I know that the SU's only need ~4 psi of fuel pressure.

Is this something I could hook up between the fuel filter and fuel rail? I eventually plan on getting an aftermarket fuel rail.

Is the 3 port fuel pressure regulator what I need to allow me to hook up the return line as well.? I wasnt sure what the difference was between the 2 port and 3 port fuel pressure regulator....

Any advise on this matter will be greatly appreciated. Thanks.

[Nissanman]

Lots of info here.

Instructions here.

They do say "NOTE: This regulator is not recommended for pumps over 200 gallons per hour."

[sblake01]

The stock EFI fuel pump is regulated to 36 psi. Unregulated, it will put out more than 100 psi which, though I'm not sure, may be well over 200 gph. I'd use an electric fuel pump designed for carbs in your case. Less chance of problems.

Edited December 16, 2008 by sblake01

[zKars]

Mr Blakeney is bang on again. Do not use the stock EFI pump without a reg.

The regulator that NissanMan has a link to requires a 3/8 diameter return line to regulate for the flow rates desired. This is far larger than the stock lines making this reg unsuitable. Don't ask how I know.

Best solution of all for stock SU's is to use a stock mechanical pump. Quiet, no wiring, simple. Here's hoping you have a head with the open casting to mount it, and the eccentric on the cam sprocket to drive it. If you have a stock 75 L28E, you very likely have all that.

I supply a set of triple 45's Solex on my stroker quite nicely with a stock pump, after much grief trying to find the right combo of high capacity fancy electric pumps and regulators to work consistently.

If you need a list of what you need, let me know. Lots of great folks here to help you get it right.

Jim

Edited December 16, 2008 by zKars

[beandip]

If you just go to the bone yard and find a RX-7 pump for a '80 car they put out 5 psi and work great . $15.00. No regulator needed.

[Carl Beck]

Is the 3 port fuel pressure regulator what I need to allow me to hook up the return line as well.?

Return from where?

You could hook up a return from the regulator - in which case the return line needs to be the same size as the feed line.

Or you could use the return line from the Carb. Fuel Rail... in which case you would not have a return out of the regulator.

A return from the carb.'s helps keep the fuel cooler at the carb.'s.

A retun from the regulator seems to be more a matter of reducing stress on a higher pressure fuel pump used where high pressure isn't needed.

I'd agree that you should replace the EFI Fuel Pump, with one matched closer to your Carb's. needs.

I use the Holly Fuel Pressure Regulator with no return line at the regulator.

Part Number HLY-12-804. It regulates pressure between 1 and 4 psi. Satin Finish

http://www.holley.com/12-804.asp

Not to be confused with the HLY-12-803, which regulates pressure between 4.5 and 9 psi. (the part numbers on these always seem backward to me).

FWIW,

Carl B.

[sblake01]

.....Do not use the stock EFI pump without a reg.

I was actually saying not to use the stocke EFI pump with carbs.

[BARACU]

I used a replacement electric fuel pump from a 72(?)Z that I got from Autozone. I mounted it in the original 280 bracket and used the original wiring. No regulator, no return line and it has worked perfectly and is dead quiet, unlike the Holley pump in my other Z. FWIW AL

[shadesh]

wow fellas.. lots of feedback and appreciated as always. I will look for that eccentric mounted on the timing gear.. if its there, I may just buy the mechanical fuel pump and install. That replacement pump from the 72Z or RX7 is also a promising idea but will it be enough to supply fuel at high rpm given that fuel will come in at a constant 4psi vs a mechanical where more fuel is pumped in at higher engine revs..?

[shadesh]

I opened the valve cover last night and I did not find the eccentric (did I spell right) on the timing gear. Now what do I do? The eccentric should be the round piece that is in front of the sprocket and is not centered.. Do I just pull the eccentric off a 240 and bolt on mine or do I have to get the whole set, the sprocket, eccentric, cam and all???

Please help.

[sblake01]

You can bolt the eccentric on from a car that has one but does your head have the area cut out for the fuel pump arm?

[shadesh]

sblake01, yes the head has the area cut out for the fuel pump arm. Anyone here have the eccentric you sell me???