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Anyone know what the output pressure of this pump is supposed to be? The one that I have cloned seems to be at about 5.5 psi.
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Re: 4656 fuel pump
As you're probably aware the ST12 refers you to the '61 passenger shop manual, which states "5 1/4 to 6 1/2 psi for V-8 engine"; the April 1960 RPO Service Operations book calls for "4-5 pounds on 1956 models, 4 3/4 - 5 1/2 pounds on 1957-60 models"; sounds like you're in the park. -
Sounds Like
it's right on the mark!
Dale.Comment
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Re: Sounds Like
It's about time something went right, without some sort of glitch or another.Comment
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Re: 4656 fuel pump
people get it all wrong about fuel pressure 4.5# fuel pressure at wide open throttle will support 500 HP as long as the flow is there.Comment
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Re: 4656 fuel pump
Clem, The reason I ask is that I know that the early Carter carbs are sensitive to too much fuel pressure and that the float valve can be overcome causing flooding. I intend to use this pump with a #360 FI unit and wanted to be sure the pressure was correct for teh application. Can't find anything in the ST 12 or the FI manual regarding max/min fuel pressure.Comment
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If I'd looked in the right place to start with
I would have found it in the "tune up specs" section of the ST 12. Correct pressure is 5.25- 6.5 psi.Comment
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Re: 4656 fuel pump
I'd rather have 4.5 psi than 5.5 psi. Easier on the bowl needle valves and floats.
DaleComment
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Re: 4656 fuel pump
What controls the fuel pressure and how would one alter it? I'm assuming the diaphram spring?Comment
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Re: 4656 fuel pump
Dale,
I have put a replacement 4656 pump on and have heard they can go up to 7 lbs. I hear many opinions on what the Carters can handle. I have a '60 270 mtr which I just installed the orig. 2X4 setup. I did have a flooding problem, but after I adjusted the float seem to be OK. Is there a replacement 4656 that only does 4.5 psi? Do you think that I will have problems down the road running 6-6.5?
DonComment
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Re: 4656 fuel pump
You have a problem when you observe a problem. Don't fix something that's not broke. If your system is working without trouble then leave it alone.
The pressure is controled by the two press-fit valves in the main body of the pump. To change pressures these valves can easily be replaced. The diaphragm spring has nothing to do with it.
Dale.Comment
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