Hello folks,

I am using a carbureted engine that has worked just fine with 1bbl, 2bbl and 390 and 500 cfm 4bbl carbs. Carbs are supplied with a new stock fuel pump through metal filter, up and over the valve cover in the suggested modification manner, through a new fuel pressure gage to carbs. Fuel is suupled through 5/16 braided steel line with AN fittings.

My fuel pressure is a steady 2 psi. Volume output matches FSM pump test in a jar. . I understand why FI guys want more pressure, but I have read in many places that the carbs, particularly 4bbl, need 4 to 7 psi. So what gives...why do so many mfgrs spec 4 to 7 for their carbs? I must be getting the volume needed at 2 psi because up to nearly 90 mph there is no fuel shortage, so I have long been more focused on volume than pressure. Sure I can up pressure by using a smaller diameter line, but to what end? What pressure on a stock fuel supply are others operating at?

rock
'64d100

2 weeks ago a friend of mine replaced the fuel pump and got a weird pump that delivers 10 PSI but LESS volume than the older pump wich worked fine (I told him NOT to try'n repair something that's working, but! ) same line, same everything, long story short, fouled plugs, the ammount of pressure was causing the needle/float assy to be open all the time, permitting the pump to flood the engine at idle.

2 PSI at idle or in revs?

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

If you're getting the volume necessary but only seeing 2psi on the gauge, my best guess is an improperly-calibrated gauge. Factory spec on the slant-6 is 3-5 psi.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Is that flowing pressure or dead-headed with the needle closed?

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Official Cookie and Mater Tormentor.