Carb Install Question
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Fleet Mechanic
Joined: Nov 2009
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Carb Install Question
I'm installing my Holley and am close to finishing. The carb came with 3/8" hose and fittings. The line coming from the fuel pump is 5/16". Will this supply enough fuel?
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
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From: Hesperia, CA
The Holley link was great info. I fought vapor lock with my truck for several years and tried everything. I tried wrapping the line with insulation, clothespins, running the line on the outside of the frame. Nothing helped. Then in finally dawned on me that it was fuel starvation instead of vapor lock. I ran a 3/8 line all the way from the fuel tank to the Mallory 110gpm under the cab and on to the carburetor. I took the stock mechanical pump off the engine, threw it away and put a blank cover plate over the hole. I can run that 460 up a 9 percent grade now with a 7k 5th wheel on the back without a sputter.
A word of caution, the Mallory, and possibly the Holley uses a motor to run the pump and somewhere between 40 and 50 thousand miles the brushes will eat up the commutator and will leave you stranded alongside the road. This happened to me on the prairie in the middle of Nebraska at midnight during a thunderstorm. I fixed the problem by mounting two and putting them in parallel with a DPDT power switch. I only run on the one pump until it burns out and then switch to the unused one. I remove the bad one as soon as I get home and send it back to Mallory to get it rebuilt.
A word of caution, the Mallory, and possibly the Holley uses a motor to run the pump and somewhere between 40 and 50 thousand miles the brushes will eat up the commutator and will leave you stranded alongside the road. This happened to me on the prairie in the middle of Nebraska at midnight during a thunderstorm. I fixed the problem by mounting two and putting them in parallel with a DPDT power switch. I only run on the one pump until it burns out and then switch to the unused one. I remove the bad one as soon as I get home and send it back to Mallory to get it rebuilt.
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Fleet Mechanic
Joined: Nov 2009
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So, now you have me thinking. Is the electric fuel pump used in the late 80's F250s suitable for this, or does it provide too much psi?
Elder User
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From: southeast Idaho
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Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
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From: Hesperia, CA
Way to much pressure. They are for EFI and around 45 psi. Ypu want no more than 7.5 psi on a carburator. 5 psi is ideal for most carbs.
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Cargo Master
Joined: Oct 2011
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From: Kenner,La.
fuel pump
84espy, If you go to an electric fuel pump take the extra step an wire it to a oil pressure safety switch. You do not want it to burn your truck down should your carburetor flood over or have an accident. Kenny
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