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shelby racer 11-01-2006 07:49 AM

Feeding csx4788
Het gang,
will plumbing the two -6 fuel lines from the fuel pumps to a fuel distribution block to a holley fuel pressure regulator (3/8 " pipe connector) to a large summit fuel filter (3/8 " pipe connector) to -8 aeroquip hose to a -8 aeroquip fuel log to a 750 cfm holley 4150hp double pumper (mechanical secondaries) on a 1965 10:1 holman moody 427 side oiler with edelbrock heads (modified to 2.19 intake) putting out ~ 525 hp at the crank give adequate fuel flow if fuel pressure is measured off the other end of the fuel log? Thanks.

Manowar 11-01-2006 08:27 AM

7 to 7.5 psi.

shelby racer 11-01-2006 08:40 AM

Okay - that is about the fuel pressure I was planning on, but will fuel FLOW be adequate with the way I was going to plumb it for a 427 fe big block? Sorry for not being specific enough

kris-kincaid 11-01-2006 09:03 AM

Yes it will be good. It would be ok if you used -6 all the way to the carb. 525hp is pretty tame.

shelby racer 11-01-2006 09:17 AM

Thanks Kris!

lineslinger 11-01-2006 10:25 AM

The set up your builder describes sounds similar to the way I plumbed my engine.
I ran 10AN hose from the pump to the intake side of the fuel filter, next in line is the fuel pressure regulator, after the regulator comes the fuel pressure guage. From the output side of the guage to the fuel log the line size is reduced to 8AN and then from the ouput of the fuel log I ran two 6AN lines from the log to the carbs. I am feeding this configuration with a Holley Black fuel pump.
With the pressure guage being placed AFTER the filter and regulator I get an accurate reading of the fuel pressure going to my carbs while being able to watch for a pressure drop when large quanities of fuel are demanded (no drop off occoured). This all runs to a dual quad set up of Holley 750's with mechanical secondaries, which holds a constant pressure of 7.2 psi no matter what position the throttle is in.
By reducing line size as you get closer to the carbs it helps maintatin pressure while still supplying a healthy volume of fuel to keep things happy.
Hope this helps.

Anthony 11-01-2006 12:15 PM

I would think so.

I ran two 6AN fuel lines, a single line combining both the electric pumps, and a single line to the mechanical pump, both lines then going to a distribution Y block, and then 8AN line coming from it to a fuel filter and to the carb.

shelby racer 11-01-2006 05:27 PM

more thanks
thanks anthony - that is exactly what I was looking for.

Anthony 11-01-2006 07:42 PM

With my first engine, a stroked 427, 477 ci, I had a problem with fuel starvation very noticible on the drag strip. I would get partway down the track, and near the end of 2nd gear, before shifting into third, when the engine would start to stumble, and continue to stumble after shifting into 3rd and then 4th, the rest of the way down the track. I could tell I was way down on power as there was little G-Force as compared to 1st and most of second gear. Initially, I had assumed it was my rev limitor, but then later realized it was my fuel supply. I was only running off the mechanical pump, a carter street pump, and I had forgot to turn the electric pumps on. The engine had dyno'd at 570 hp. I had two 6 AN lines running forward, one line running from the tank to the mech fuel pump, entering the fuel pump with a 90 degree elbow. The other 6 AN line ran from both of the electric pumps to a T-fitting on the outflow of the mechanical pump, combining the outflow of the mech pump with the outflow from the electric pumpd, and then up to the filter and then the single carb. To me, it looked like there would be flow restriction at the 90 elbow at the mech pump inflo, as well as at the T-fitting at the mech pump outflow.

With my second engine, I again ran the two 6AN lines, one from the tank to the input of the mechanical pump, but connected with a 90 degree radias fitting instead of a 90 elbow, for better flow on the suction, low pressure side. Instead of running a T-fitting, I put a 90 elbow on the outflow of the mech pump due to space limitations, confinements, figuring that the 90 elbow won't limit flow as much on the outflow side compared to the inflow side. I then ran a 6AN line from the mech pump outflow elbow to a Y-block, also connecting the other 6AN line from the electric pumps, and then an 8AN line from the Y-block outflow to the filter, and then carb. I have yet to really test it, but the car was chassis dyno'd, put out est 570+ flywheel hp without any fuel starvation problems, running the eletric pumps as well. I ran the car on the street with just the mech pump, and it didn't stumble. I really need to test it on the track to see if this set-up is better, which I think it is.

shelby racer 11-02-2006 08:23 AM

It's "just" a street car
Thanks anthony,
my little cobra is going to live its life on the street. I have 2 road racing mustangs that are faster and I don't feel as bad about them getting rock and rubber chips. I am planning on taking my cobra to the western states cobra bash and checking out the track in reno though, but I figure I will be with other cobras so there will be less chance of damage.

wtm442 11-02-2006 07:42 PM

Avoid 90 degree fittings like the one shown in the outlet port of the fuel regulator. If you must turn 90 degrees, use one of the high flow bent tubing fittings.

lineslinger 11-02-2006 08:40 PM

Sometimes 90's can't be avoided, such as the 90 fitting feeding the fuel log on wtm442's small block. But he is right, as a rule the more 90's in line the more flow restriction realized.
A single 90 in a low pressure system conducting a fluid with the viscosity of gasoline is of no consequence. Now if you are pumping oil at 100 psi that changes everything, I was careful not to include any 90 degree fittings when designing my oil circulating/cooling system.

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