Sard fpr on 12a Nikki carb
 

Hello there,

I'm is the process of getting my sa ready for some power. It is an old ITA car, nothing left but the bare necessities. So I don't know what any of the vacuum ports or anything are. Just wondering if anyone could make my life a little easier.

Since this is going to be temporary til I get a carb for the BP or PP motor I'm working on, I was wondering if anyone knows what pressure I should be running at. It's got a RB header and Mazda Comp breather and an 8psi fuel pump as far as aspiration goes. Not sure what the carb can handle.

Any pointers in the right direction would be appreciated.

in the old days Paul Yaw would have sold you a lab grade pressure gauge, and then told you to run somewhere between 1.5psi, and about 2.5psi. the gauge is kind of important because a 0-5psi gauge is accurate in the ~2psi area and a typical 0-15 psi gauge isn't.

to figure out what is better between 1.5 and 2.5psi, you basically need to try it and see what the engine likes

That's what I was looking for. I have high hopes of building a motor to withstand more, so I'm not super concerned about how perfect it is for now. Just a baseline.

anyone know what vacuum I should use with the fpr?

None. The fuel pressure regulator should only reference to atmosphere, or VERY specifically, the atmosphere in the region of the float bowl vent. Since you're naturally aspirated, you don't have to worry about that much unless you have a very efficient air inlet and plan on running 170mph down the backstretch. (Spoiler: Not with any flavor of Nikki you're not, so don't worry too much about it)

I have no idea how much pressure I used to run on my Nikkis. I would install the Holley 6psi pump and the Holley 1-6psi regulator and drive it until it felt good on the highway under cruise. Usually this resulted in the adjuster backed most of the way out, so maybe 1.5-1.75psi?

I did find that there was little difference trap speed wise between so rich it makes the plugs sooty, and so lean that the ground straps melt off, so i just tuned so it felt good driving down the highway, and it seemed pretty happy there at WOT too.

Good to know. Thanks for the info guys.

While we are on this topic.. Between the stock gas tank and fuel pump there is a small Junction block on the fuel line. Does anyone know its purpose?

A roll-over fuel cut check ball. How safe do you feel knowing it's under there?

Haha nice. Well if for some act of God I could roll it, I'm pretty sure my cage would just make it finish rolling. And if that doesn't work, the kill switch will!

Consider it gone.