Ok im changin my 86 f150 from efi to carb. Im at the point where im figuring out my fuel delivery. I have the in-tank pump as well as a high pressure pump on the frame. I know the high pressure pump has to go no question.

Can i use my stock in-tank pump with an adjustable pressure regulator to get it down to about 5 psi?

If not can i just cut the power to the pump and put an inline low pressure pump and be fine?

 

You can use a bypass regulator with a return on it and it will be fine. You don't even have to mess with getting rid of the HP pump if you don't want to.

 

Bypass regulator? I think I've seen some but aren't they to the tune of like 200 bucks?

 

But it's a good way to go IMHO - leave all existing pumps in place, and simply replace the EFI feed & return lines with said regulator and a feed to a carb.

Your existing pumps are designed to be running continuously with no (or limited) restriction of their flow.

Merely constricting the output is going to put stress on them and burn them out faster.

Closest analogy I can make is the human body... cholesterol & plaque build-up in your arteries constricts them, this puts undue stress on your heart and it will fail sooner rather than later.

Another analogy would be a swimming pool's filtering system, where the pumps are designed to run at a high rate of flow with no restriction.

Your existing motors are designed for a specific task and to operate in a specific manner...

...Many people don't know that, and burn out electric motors prematurely...

For example, starter motors, windshield washer motors, are both designed to be run in short bursts separated by a cool-off period.

Operating your starter motor continuously for half an hour - say, while you're trying to jump-start your car - will burn the thing out, leaving you with a worse problem than you originally had.

 

Ok I get what your sayin...you wouldn't happen to have any part numbers for some I could look at

 

Here's what I have.

Holley 12-842 - Holley HP Billet Fuel Pressure Regulators - Overview - SummitRacing.com