I've installed the K&N electric pump from MSA with my ZTherapy refurbed Hitachi SU's.

http://www.thezstore.com/page/TZS/PROD/classic17a09/11-3078 

The MSA write-up for this pump says "no regulator required". The car runs fine without a regulator and I see no signs of the carbs dumping fuel. I've also heard that the stock mechanical pump on a 240Z puts out 5 - 6 PSI which is pretty much in range with the K&N pump. Any thoughts on whether I should throw money at a regulator and why? If I'm convinced I need a regulator I'm guessing this regulator / gauge combo would work okay?

http://www.lceperformance.com/Fuel-Pressure-Gauge-Kit-Low-Pressure-Carb-Only-p/1035056.htm

 Never heard of the Z mech. pump putting out that much pressure. Not saying it's not true, probably just my ignorance. IMO, I'd put a regulator on it. 3 psi is enough pressure to get fuel to the float bowl. If an engine is starving for fuel at 3 psi, it's got a fuel volume problem not a pressure problem. In the long run, the extra pressure could cause premature failure of the needle and seat valve. Not a good scenario when the carbs sit above the exhaust manifold. One other thought. It's possible that extra fuel pressure could raise the boiling point of the fuel and help a heat soak problem.

I am just curious. Why did you go with an electric fuel pump? Did you use an oil pressure switch or inertia switch to cut off power in case of an accident?

You can find the fuel pressure range needed in the EF section of the FSM. 

Before you buy a regulator, you might try installing a fuel pressure gauge. You can get a fluid filled gauge from Amazon at a reasonable price: https://www.amazon.com/gp/product/B000CIH38M

You'll also need an adapter for the gauge. This is one for regular fuel line: https://www.amazon.com/gp/product/B00093CL3M

After that, if you need a FPR, and I doubt you will, here is one. You'll need 3/8 NPT to 5/16 barbed fittings, too. I also recommend getting fuel-resistant teflon tape. https://www.amazon.com/gp/product/B00029JC6M

 

FSM says mechanical fuel pump pressure should be 3.41 to 4.27 psi.

@SteveJI went electric because I wanted to. Inertia switch.

I like the idea of trying the gauge to see what I'm dealing with.

I find a gauge to be very helpful. It allows you to see that pressure is correct, and instantly rule out (or verify) fuel pressure as cause of engine trouble.  Get a good gauge, though.

You can run hoses from the float bowl vents to clear plastic catch cans (I use shiracha bottles) to make sure the bowls don't overflow. 5 to 6 psi might be enough to overpower the valves.

Edited November 16, 20177 yr by Stanley

Funny, I deleted my mechanical pump this week due to to leakage, and I swear just running the OEM electrical pump in the rear I get worse milage.. maybe its because finally it pulls hard enough to where I'm just abusing it. http://www.nicoclub.com/service-manual?fsm=260z/1974/EF Fuel System this file indicates that it should be outputting a max of 4.6 PSI, I wonder what the fuel rail see, the diameter of the pipe changes from 5/16 to 1/4 at the fuel rail....

 

 What intertia switch did you go with? Ford? 

On 16/11/2017 at 11:57 AM, Mark Maras said:

 Never heard of the Z mech. pump putting out that much pressure. Not saying it's not true, probably just my ignorance. IMO, I'd put a regulator on it. 3 psi is enough pressure to get fuel to the float bowl. If an engine is starving for fuel at 3 psi, it's got a fuel volume problem not a pressure problem. In the long run, the extra pressure could cause premature failure of the needle and seat valve. Not a good scenario when the carbs sit above the exhaust manifold. One other thought. It's possible that extra fuel pressure could raise the boiling point of the fuel and help a heat soak problem.

I read that you need a mimimun of 3.4 psi. I have both of my su carbs set at 2.65 turns clockwise and the car is starving at idle. Did a test with a gauge near the cam and it did not reach to 3psi.  Could my pump be defective? I have bought 3 of these lousy electric pumps and always finish ditching them for the same cause. 

Edited November 19, 20177 yr by jalexquijano

 Don't know what to make of the slightly low pressure but if the engine was starved for fuel, you'd notice it when accelerating, at higher RPM's and when pulling hills. That's when the engine is using the most fuel. At idle the engine is only sipping fuel. Keep in mind that the fuel mixture doesn't rely on fuel pressure. The pressure is only to deliver fuel to the float bowls. The engine would run fine at any speed if one eliminated the pump and used a gravity feed to supply the bowls with fuel.

 What symptoms make you think the mixture is too lean at idle?

My gauge works great. Here's my secret:

http://www.mcdanielcontrols.com/

4 hours ago, Mark Maras said:

 Don't know what to make of the slightly low pressure but if the engine was starved for fuel, you'd notice it when accelerating, at higher RPM's and when pulling hills. That's when the engine is using the most fuel. At idle the engine is only sipping fuel. Keep in mind that the fuel mixture doesn't rely on fuel pressure. The pressure is only to deliver fuel to the float bowls. The engine would run fine at any speed if one eliminated the pump and used a gravity feed to supply the bowls with fuel.

 What symptoms make you think the mixture is too lean at idle?

Okay speed up nice but at idle the rpm tend to fall from 1100 to 500. If i go up a hill from 1st gear position i need to pull the choke so the rpm does not fall. Could there be some clog in the line?

 No clog. If pulling the choke instantly gives you more power, (the engine is warm, right?) Increase the mixture from 2 .65 turns to 2.75 turns and try the same route again. I still want to see the plug colors. You could still have one carb lean and the other rich. Also what weight oil are you now using in the carbs?