So, I have 5lb of fuel pressure at the carb. I need 10 to 12 for my nitrous.
I have sitting in the basement an 8lb electric fuel pump that I
used to boost a larger electric fuel pump for fuel injection.

Can I run the current mechanical and add the electric to get more pressure?
If so should I run the two in line together or run a loop around the mechanical?

Car is also hard to start since I replaced a blown power valve.
Seems it just takes a while to get any fuel. I'm thinking the electric could be used to
prime the carb before I start it.

Any thoughts?

Holley 750 old pre 7140. 6.5 Power Valve.
Have 15lb of vacuum at idle.
Also moved battery to trunk the same day as I replaced the power valve. Don't think it is related.
Car turns over just wont fire for a few seconds. And just to be complicated it got new exhaust the same day. 3" with an x-pipe.

 

You'll need to split the line prior to the fuel pump and add the electric, or split it back by the tank and add it there. The Holley wont like 8lbs. of peressure, and it will flood out or ruin your float needles and seats. Holleys will have issues with more than 6lbs. of pressure, I've tried it and learned the hard way.
Take the electric straight to the nitrous solenoid and hook it into a separate sw. so you can arm the nitrous and the electric pump off the same sw. That way it wont be trying to pump all the time and go bad too soon. No need to run it if you aren't using the nitrous.

 

hmm, ok.

So do I need to bother, or can I just run a larger jet on the fuel side of the nitrous. I was thinking I needed a little more pressure on the carb side. Guess not. I Googled it and you are correct max pressure to the carb is 7lb.

 

is your system a dry system or do you have a wet shot going on too. If you are starving the car for fuel and you are shooting No2 only then I would look into adding a fuel injector. to add a wet shot to assist in the fuel requirements.

Massey

 

I ran 9psi with a 175 shot. My pump was a Holley blue. What I did was regulate the carb to 6psi. Then the nitrous supply was regulated to 9psi.

So basically I ran -8 from the tank to a tee. The tee went to two regulators. One went to the carb the other to the nitrous solenoid. After the regulator I ran -6 if I remember correctly, split to the fuel bowls. The other regulator was simply in and out to the solenoid. I also had two pods on the cowl with pressure gauges for both. It was a plumbing nightmare but I only ran it a few times so it was not on the motor for long periods.

The biggest deal is the timing in my opinion. My car had an MSD timing **** that allowed me to pull up to 8* out of the dizzy without popping the hood. Worth its weight in gold when out bracket racing, then at the end of the day just pull out the timing and arm the system. I also ran a cheepy little nitrous delay that was adjustable up to 1 sec. It had 10 dip switches in .01 sec per switch. All this let me tune from 10.84 (best at the time) to a 9.97. Good luck, don't break your stuff.

 

It is a Nitrous Express wet system.
Car is not lean, not at all. The wideband o2 sensor is in the mail.
I plan on running about 12 AFR. It will be very rich at all times.

So, I really do need the higher pressure for the nitrous. Then, since I have the electric fuel pump, just sitting, it would probably be best to run it just to the nitrous and power it off the same switch.

Will also look at the fuel regulator on the carb side.
Nitrous express want 12 lb if I go up to the 150 shot.

All that really matters is the AFR of the motor correct.
As long as the car doesn't lean out Im good.
So I can just test with the small nitrous jets and watch the AFR's.

 

Electric fuel pumps feeding mechanical pumps will cause really ugly situations if the diaphram ever went bad on the mechanical pump as the electric would fill the crankcase with gas and dilute the oil to a point it would most likely seize the engine. You can run both pumps using the electric for the NOS, and the mechanical to the carb, or you can do as Damon mentioned and run two regulators with one to the carb and one to the NOS.
Be sure you've got a pressure kill sw. in the line to the NOS so if it ever loses fuel pressure you wont go lean and fry a few pistons under full throttle!

 

I have a wide open throttle switch, so I can just let up on the peddle to stop the nitrous. I will also have a digital wideband o2 gauge on the dash.

I am going to call nitrous express and see if they can tell me what jet size to run on the fuel side with 6lb of pressure. If they say I cant do that I will run the electric to the nitrous and the manual to the carb.

Thanks for the help
I will let you know how it goes.