Mechanical Fuel Pump Pressure Question
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
Mechanical Fuel Pump Pressure Question
I was using a stock GM mech fuel pump but was getting high pressures at start up which would cause a very rich condition. The pressure would drop after a while. I replaced it with a holley mechanical which they say does not require a regulator. Supposed to maintain 7 1/2 psi. Well, I am having the same problem with it. It goes up to about 15 psi then after about 10 minutes at idle it dropped down to about 6 psi. This floods the engine out and makes it almost imposible to keep running. Should I just put in a pressure regulator or should I replace the pump and try again?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,738
Likes: 53
From: Bogart GA
A stock small block pump may have a problem feeding my 427 at wot. Are there any other mechanical pump manufacturers out there that make reliable pumps? I tried a big block stock pump on my small block and it broke the pump arm. I guess the big block pumps have a longer lever arm. Going to put a reg on anyways for now.
Burning Brakes
Joined: Jun 2002
Posts: 792
Likes: 2
From: Norcross GA
I don't know what carb you are running but I was just reading Doug Roe's book on the Q'jet and he indicates anything over 4 - 6 psi to feed the beast can create flooding issues. He made no distinction between the 750 and 800 cfm Q'jet.
Last edited by Bobchad; Dec 26, 2004 at 10:43 PM.
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
I would be checking the float and needle and seat in the carby if it is flooding at idle. The standard needle and seats should be able to hold that sort of fuel pressure.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Originally Posted by KJL
A stock small block pump may have a problem feeding my 427 at wot. Are there any other mechanical pump manufacturers out there that make reliable pumps? I tried a big block stock pump on my small block and it broke the pump arm. I guess the big block pumps have a longer lever arm. Going to put a reg on anyways for now.
