Fuel Pressure...

[Hallett19]

What is good fuel pressure for my 460 w/ holley 750 vac secondary carb ?

[77charger]

6.5-7.0 is preferred while running.But you need atleast 5 pounds

[Hallett19]

How about 11 ? :rolleyes:

[Taylorman]

I would say you need a regulator. Holley says you can damage needles and seats if fuel pressure is to high. I run Edelbrocks and they say 5.5-6 is adequate. My pump puts out 9 and I have never had a problem so I am just leaving it as is.

[Squirtcha?]

I believe that Holley says the needles can take 8 lbs. I'm running 9 with mine and it hasn't been a problem. I've got some friends that are running even more than that with their blower motors.

[Hallett19]

What happens when the pressure is run too high for too long ? damage the needle and seats you say ? so go buy some new ones if I am having problems ? I put a new carb on and it ran fine for a while, then, randomly, out of nowhere, the motor decided to not idle really good, backfire a bit and run shitty at low rpms's. I only ran it at 11 1/2 lbs of fuel press. for about 30 min !!That and the secondaries arent really opening. Any help ?
[ May 27, 2003, 09:43 AM: Message edited by: Hallett19 ]

[Hallett19]

I'm not kidding here guys, I need help :D Oh yeah, and if it helps, I put on a regulator and set it to 6.5 psi and I am still having the stalling/hard starting/backfiring problem, but its kind of intermitten ..... help!!
[ May 27, 2003, 06:14 PM: Message edited by: Hallett19 ]

[skeepwerkzaz]

simma dawn nahh. Too much fuel pressure=bad needle and seat=bad idle,rich mixture, and shitty performance. Missed you @ parker. Went off, wes was in RARE form.
clay
http://www.***boat.com/image_center/data/500/4851st_1-med.bmp

[BK]

If your running 11+ psi I would say that will cause you problems with needle/seat and the backfire (if your not running pv blow out protection) would cause you to blow out your power valve. If you did blow out your power valve you'll probley have a bunch of fuel getting dumped into your motor at idle and have a pretty tuff time. Have you checked your spark plugs?

[Chris J]

If you run too much fuel pressure sometimes you can hear the needles buzz right after you shut the motor off. The presure over comes the needle and seat and the floats will vibrate. Usually fuel will drip down the booster for a while and basically flood the engine which cuases the hard starting you are having. If its real bad it will cause idle problems too because its dumpping gas faster than the motor can use it.
After you shut the motor off look down the carb (carefull watch out for a delayed backfire) and see if the boosters are dripping gas. If they are you'll need to replace the needle and seat and reduce fuel pressure to prevent it from happing again.
NOTE: Having the floats set too high will cause the same problem. In fact by lowering the floats you can get by with more pressure. Although there is no advantage to running high fuel pressure. The fuel pump is only used to keep the bowls filled with gas (or over filled if you have too much pressure).

[Hallett19]

when I shut the engine off, I get a delayed "final crank" like a last breath before dying if that makes any sense, and it steams a bit from the primaries, so it seems like it might be dripping from somewhere. Even after I cut the fuel press. down it still does it then gets a hard start after it dies on its own. I hate carbs, I want to put a fuel inj. system from an econoline van on my 460 !!!