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Old 06-12-2004, 04:06 PM
dacuda dacuda is offline
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Default fuel pressure problems

i seem to be having some problems with my fuel pressure readings.i set my pressure at the regulater and it reads 6 lbs at the guage and go for a spin around the block and get it warmed up and look at the guage and it will read 3 lbs or even as low as zero.i adjust it up to 6 lbs again and later it will read 9 lbs.what gives? this is all new stuff.i am tryting to adjust my timing and carb settings but feel im getting false readings cuz of the pressure fluctuations.i get a low rpm stumble off the line and think im getting fuel starvation.should a guage change pressure as the engine warms up.?is my pump faulty or could it be my guage.i run a holley blue ,aeromotive regulator to an aed modified holley 850 dp.this motor makes 575 on the dyno so i know its lacking somewhere.i here different things concerning line size ,pump size,and so on.barry grant says i should be running a bigger pump that puts out at least 300gph.i am also gonna give the "fill a 1 gallon can up in under 30 secs" thing a try .can someone tell me what they are running so i can do a comparison .i guess ill start with a new guage and see what happens and wait to see what everyones input is.thanks
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Old 06-12-2004, 05:20 PM
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Geezer Geezer is offline
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Biggrin Doing the math...

Using a common math calc, you can determine the fuel the engine needs to support the 600HP you are expecting...

600 x the BSFC average of .5 = 300#/HR fuel. [.5 assumes the engine is fairly efficient]

Gas weighs about 6.4#/gallon. [.77 sp gr x water at 8.3#/gallon]
Dividing the wt of a gallon into 300# = about 50 gallons per hour, at 600HP.
At the psi that blu pump is operating at,[about 6psi], the question becomes, "does the pump have the ballz to push that much fuel, considering bends in the lines, line size, acceleration G forces"??
I'm betting not....

As for the gauge, I recently saw some posts about that same problem.. Engine cold=OK, engine, fuel, gauge gets hot = No good.
If that's one of the "mini gauges", screwed into the regulator, I would not trust it.
I check alot of them on my injector bench, and find them as far as 5psi off, non linear, non repeating.

HTH,
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Old 06-13-2004, 01:57 PM
KEVSDODGE KEVSDODGE is offline
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Default

Hello,just installed a holley blue/with regulator,same stuff.I called a buddy,and talked to several guys,just check it cold,when the gauge get`s hot it act`s erratic.Good luck!
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Old 06-13-2004, 02:10 PM
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threefortyduste threefortyduste is offline
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Default

something is messed up, because if you really had zero fuel pressure, the car wouldnt run, 0 PSI=0 Fuel=0 Combustion
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Old 06-13-2004, 08:02 PM
RobbMc RobbMc is offline
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Default It's the gage

Gages mounted on the engine read lower the warmer the gage gets. Liquid filled gages seem to be the worst.

Try mounting the gage remotely where it won't get hot.
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