Fuel Pressure Gauge Needle Fluctuating ?

[Mike Gaines]

Mike,

Would a fuel pressure gauge isolator help with this problem?

A fuel pressure gauge "isolator" is used so you can mount a fuel pressure gauge "inside" the cabin of you car (not on the windshield cowl). The Isolator merely converts the liquid pressure in the line (that is "outside" the cabin) to NON-Liquid pressure to actuate the fuel pressure gauge in the cabin.
This Isolator is a safety item so you dont have liquid gasoline entering into the cabin of the car..so if the fuel pressure line going to the back of the interior mounted gauge would break then you would have gasoline sprayed all over you and the inside of the car.

 

[ozymaxwedge]

Mike I stole this from Moparts site. Check his 1000' to full track mph.

current combo is a std stoke .030 440
BG 995 cfm King demon RS on an M1
11.5 to 1
ex rebel Engle solid cam and lifters
sidewinder heads with a gasket match and not much else
Harland sharps
glide with a 4k converter
4.56 gears
four link in a duster
best so far with the footbrake
1.46 60ft
6.6 1/8th @ 99mph
8.9 1000ft @ 124mph
10.91 1/4 @118mph
fuel pump proved to be too small and couldn't keep up.

it had whats called an Aeroflow black 140 equivalent to a holley black. all -8 lines from cell to carb. I knew it wasn't going to cut it but up until then it had been running quicker and quicker, guess I found its limit.

 

[dvw]

A lot depends on how much bowl capacity you have. Two carbs have twice as much bowl capacity. They can actually run less pump. Jenkins went pretty fast on 1 Holley blue back in the day in PS.
Doug

 

[Mike Gaines]

Ozy....very very interesting. 124@1000ft then [email protected] he shut it down or actually run out of gas ???

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Ozy...what is your fuel system layout ?

 

[ozymaxwedge]

Cuda, Sump welded to stock fuel tank, rear exit -10 line to 300 Magnafuel pump that has a -8 bypass back to tank, -10 line to BG 4port reg and -6 lines to carbs. Has been 130 mph on street tyres and will go faster now with the tunnel.



63 Ply, Front mount custom tank, -10, BG 400 pump to BG reg and -8 to carbs. Over kill I know but the car was running 9.2 @145 on the bottle as well so I was not going to lean out


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Ozy....very very interesting. 124@1000ft then [email protected] he shut it down or actually run out of gas ???

?

Story is that he was running out of fuel. I would be a little concerned with your system.

 

[Bigal75]

I'm having the same type of issues with my 140 pump.. I can't jet it rich enough. 750hp with a 1050 dominator.

 

[hangn0ut]

Followed this thread and I must say, no way is it necessary for the return line to be as big as the pressure line in a bypassed fuel system. Dont confuse volume and pressure. The bypassing of a modest volume will result in a large drop in pressure. I run an Aeromotive 1000 pump feeding a 1/2" line to the regulator mounted next to the carb. I wanted to knock down the pressure up to the regulator so I tee'd in a dash 6 line. In that line I put a bypass poppet valve. I set it to open at 16psi. With the car idleing I can hear the bypass cycling open and closed. And its closed a lot more than its open. I'am sure this is not an ideal setup but my point is that bypass takes care of the excess fuel very easily. If i took the poppet out of the bypass this system could not build no more than maybe a 1/2lb of pressure. Maybe a huge pump,feeding a dash 12 line might build a few pounds of pressure but that 6 line would simply flow more fuel with the added pressure.

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The duster with the funny timeslip. Cars running 6.6 in the 1/8 will pick up 20-25mph by the quarter. This car picks up 25mph in 340'. A normal car takes 660' to get the 25mph. Sounds to me like a big bottle was opened at the 1/8. And closed at the 1000' mark. A car that picks up 40 mph in the second half is usually around 160 or so in the quarter. Quite a 440 in that car.

 

[Mike Gaines]

I'm having the same type of issues with my 140 pump.. I can't jet it rich enough. 750hp with a 1050 dominator.

What is the nature of your problems ?

 

[dvw]

What is the nature of your problems ?

What leads you to think it's not rich enough?
Doug

 

[Bigal75]

My plugs are white and the car lays over and my af gauge climbs up into the 14s. I can't get them down even if I jet up to insane sizes. 99s square is still too lean at wot WITH a power valve.

 

[ozymaxwedge]

My plugs are white and the car lays over and my af gauge climbs up into the 14s. I can't get them down even if I jet up to insane sizes. 99s square is still too lean at wot WITH a power valve.

Keep that up and you will loose that engine, 750 hp needs more than a 140 pump.

 

[Bigal75]

Keep that up and you will loose that engine, 750 hp needs more than a 140 pump.

Oh I agree! New pump and fuel log on the way!

 

[ozymaxwedge]

What pump did you go for ? I have just put a Magnafuel Quickstar 300 on my Barracuda and love it, half the noise of a BG400.

 

[Bigal75]

Mallory 250. It fits right in since I'm plumbed with -8.

 

[hangn0ut]

With a small motorcycle battery and some relays you can hit a fuel pump with 24 volts only at full throttle. This really raises both volume and pressure of any electric fuel pump. A different way of getting there.