fuel system - pump requirements mikuni

[george schiazza]

I have a 240 z engine with triple mikunis

Any help on recomended fuel pressure settings

The car is basically stock - with headers

The existing electric pump has no markings and was supplied some 20 years ago with the carbs

any help or suggestions would be appreciated

[mark belrose]

According to the Mikuni PHH Carburetor Service Manual, the optimal fuel pressure is 2.84-4.98 lb. I'd recommend getting that manual since it's a good reference for PHHs. I see them on ebay frequently for $10 or less.

I've been using a cheap regulator from Summit for years with my Mikuni 50PHHs and have never had any problems.

Mark Belrose

'70 restored SCCA C Production 240Z

[george schiazza]

Thanks Mark

I had just found the manual with a box of different jets

The car had been sitting for approx a decade

I've found a holley pump with regulator that should work fine

I have the tank out and have already found a replacement

Still have to go through and flush all fuel feed and return lines

I may surrender on the tank vent and purge system and try something less elaborate then was originally supplied

thanks again

[Curtis240Z]

When I used to run Mikunis I set the regulator to 3 psi and it ran fine for many years. Flow is what you want not pressure.

[beandip]

A couple of years ago we tried a RX-7 pump I had on a stroker with tripple Mikunis and it worked great. This was my pump but another's engine. I have since installed it on my Z with SUs and again it works great. We didnn't find any lack of flow on the stroker and I tested the pressure at just a shade under 5 psi. the pump is from a '79 rx . I like the pump on my Z because it is quiet and can hardly be heard even when the engine is not running . I have however installed a oil pressure switch that activates the fuel pump only after the engine has 5 psi oil pressure . Also I installed a inertia switch so in the event of a crash the pump will stop running . Crispy critter is not something I want happening . Gary:rambo:

[ZIII]

As Curtis says, flow is your main concern. If you have a Holly Red top you will do fine with the flow (97 gph) and you don’t even need a regulator as you will probably be somewhere between 4.5 and 5.5 psi. Of course, a regulator will allow you to fine tune things.

The RX7 pumps also work really well and they are much quieter than the Holly’s. My Holly is noisy despite the fact that I built a special bracket for it and isolated it with large rubber bushings.