Haywired

My fuel pressure when the engine is cold is at 6.5 PSI , after the engine gets hot it drops to 2.5 PSI and stays put. My gut feeling is that this is not correct butI thought I would ask to be sure. Is the stock style pump enough for a 289 with a 570 , comp 256 cam and headers? It is still the 5/16ths fuel line.

Thanks in advance

Stepman

Yes, the stock pump will move plenty of fuel for that combo. The 6.5 sounds a little high but I don't think I'd be worried. Do you have any drivability issues?

Haywired

Its not the 6.5 PSI but the 2.5 PSI that bothers me, I do have some driveablity issues that I am trying to narrow down, that is why I a starting with the pump. Also my clear fuel filter is just about down to a trickle instead of mostly full

JMD

As long as you are not running out of gas under load 2.5 psi is fine.....

And, chances are that you will not run out of gas, 2.5 psi is ok for most carbs.... as stated it is the high pressure that will get you in trouble,,, it can push the needle valve out of the seat, making the float of no value, flooding your engine.

In my experience a carburetor will work just fine with very little pressure, with flow being the key factor.

The range of pressure you are seeing is not really common.

You might want to eliminate your condition by installing an aftermarket fuel pump in addition to a fuel pressure regulator. I would shoot for about 3.5 or 4 psi for most carbs. I think the 5/16 Fuel line is ok for your combination.

jlg2002

2.5 is low it should be around 4-6 psi and put out about a pint in 20 secs which is the more important spec.

Haywired

I think it is a volume problem more than a pressure problem or maybe both. Like i said before the clear filter is horizontal and not evena quarterfull of fuel, I understand that it will never be full but it should a least half full.

67mustang302

Lack of pressure comes from a lack of flow. Pressure is the resistance generated to the pump flowing fuel, if the pressure is low then flow is prolly low(or the gauge is wrong). Does it cut out at high rpm? Even at low psi, if it still flows enough and you have no fuel delivery issues, then you should be fine. Check your oil though and see if it smells like gasoline, if the pump is going and the diaphragm is leaking it will dilute your oil.