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just1n962

4bbl 280z swap fuel pump issues.

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So I have my swap completed and I have been running a little 40 dollar pump from autozone with a 35 GPH flow rate and 4 PSI and it seems as though my holley 4bbl needs a good bit more than that... With the carb tuned I can now get it to idle nicely and I even was able to take it up the road a little but if you put your foot down a little and get the thing past 3000 rpm it wants to shut off. It's just not getting the fuel.. Now I know that I should have the 80 GPH flow rate pump but it's just so expensive... I still have my fuel injection fuel pump and just ordered a pressure regulator. Will the regulator be okay under the fuel injection pump? I'd appreciate any help here. (And please don't tell me how I should have stuck with EFI)

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Just a simple 4.5 to 9 psi regulator off of amazon. By bypass line do you mean a line that will allow fuel to return to the tank? If so then yes it does. 

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I would think as long as the pump can circulate the fuel and not be dead headed then it will work. Might be loud if the regulator is too restrictive...

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I don't think there's any way you would ever be able to consume 35 GPH. I don't think fuel pump capacity is the problem.

Note that I'm not ruling out fuel starvation, but if there is starvation, I don't think it's because the pump is only rated for 35 GPH.

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The carb never actually consumes that much. That's how they measure the things but the carburetor itself has a built in regulator that opens and closes depending on how much fuel the carb needs. 

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35 gph = 132,000 cc/h = 2200 cc/m  That should support about 330 HP.  Your pump should be supplying plenty of fuel.  https://www.rceng.com/technical.aspx

Check that it's actually able to flow that much.  Disconnect the return line and see how much comes out.  Measure it if you have a container.

Is it a new Holley, or used?  

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2 hours ago, just1n962 said:

Just a simple 4.5 to 9 psi regulator off of amazon. By bypass line do you mean a line that will allow fuel to return to the tank? If so then yes it does. 

Thought you said there was.

Do you know what the fuel pressure at the carb inlet is?  And flow?  If you're filling the float bowl at a low rate it might be that the flow rate is just too low, not because of the 35 gph pump, but for other reasons.  Clogged filter maybe. 

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That's for the regulator that I bought off amazon that I don't have yet. What I'm currently running is the cheap pump with no regulator straight to the carb. I'll put the pressure regulator on if I switch back to the more powerful fuel injection fuel pump though. Hmmmm no I do not know the fuel pressure and flow at the carb inlet. How would I go about finding that out? 

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If I had your question, the first thing I would do is to disconnect the inlet line to the carb and measure how much fuel comes out with the pump running.  If it's not close to  35 gph then there's a restriction somewhere and a higher rate pump probably won't help.  Just get a jar or a cup from the kitchen, collect over a known time, then do the conversion to gph.

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I just completed the carb conversion on a 78 280.  Used the Arizona intake and Holley 390. Running a Holley fuel pressure regulator and the fuel pressure gauge reads  3.5.   TIming was a bit of an issue at first as it was advanced a bit with my fuel injection.  It was hard to get her to idle properly....  Retarded it some and she ran well after that.....getting good gas mileage to, but she lagged badly on hard acceleration.  Went back and slightly advanced the timing to find a middle ground and she took off like a scalded dog.......but still had a bit of lag on acceleration....so I changed plugs from the NGK BPR5ES-11 to the NGK ZFR6F-11.   That combination did the trick for me....

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