paulmoore

In my quest to work out the kinks in my newly assembled 383 there hve been quite a few people that have really taken the time to help me out. Sonix, F-BIRD'88, jbenge, and others I'd like to thank you. I have another question for you. I keep going over everything in my head, thinking about different things that can be causing some of the problems that I have. F-BIR suggested that instead of running stainless steel braided hose from the tank to the pump I should either...

A. Run hard line fromt the tank to the pump or

B. Install an electric pump in the ine by the tank to pressureize the line up to the mechanical pump.

When I got to thinking about it and went outside and looked at the system again, I realized that I have my big a$$ 40 micron Russel Profilter on the inlet side of the mechanical pump. Now What I wsnted to know is a mechanical fuel pump designed to suck through a filter as a restriction or would it rather pump out pressure through the filter as a restriction? I kinda like the ideal about installing a Carter electric fuel pump because it does not require a regulator hence I won't need to drop the exhaust and rear end to get to the gas tank. This is something that I am going to look into further.

sofakingdom

iTrader: (1)

Mechanical fuel pumps (or any other kind for that matter, but those in particular) are VERY POOR at sucking through an obstruction.

If you're experiencing a problem, replace the filter with a section of line, and see if it's better.

See my signature.

F-BIRD'88

In the picture of your motor and under hood area, the fuel filter is next to the hot hot hot headers. Acts like a big heat sponge. Remember what i said about how fuel will boil real easy at a lower temp than normal if it is under a partial vacuum (low pressure) such as on the inlet side of the mechanical fuel pump. About the worst place for it. garrantied vapour lock. All you want on the inlet side of the pump is maybe a Screen filter to trap any large chunks that might get caught in the fuel pump. Any inline restriction at all on the inlet side will cause the fuel to boil in the line that much more reeadily. A pump cannot move fuel that has even minor bubbles in it. Thats vapour lock.
If you want to run the carter 72GPH pumps to pressureize the feed line you will need two of them in parralel to feed a 500hp motor. At that point you could remove the mechanical pump if you wanted to. The mechanical pump picks up heat as well and contributes to the overall problem of fuel perculation.
At any rate the filter has to be moved. Put it far away from the heat and on the pressure side. Mechanical pumps rarely get clogged with dirt. Ya need the filter to protect the carb needle and seat from not sealing (flooding).
Plumb the inlet side of a mechanical pump with all hard line.
You will need a short lenght of flexable line to jump from the frame to the motor near the pump. keep it SHORT make sure it does not collapse or kink when hot and running.

Like I said I gave up on the mechanical pump on my car even thou it has plenty of pumping capacity 130+GPH to feed my motor. Was on a 550 HP 11sec nova and on a 500hp small block offshore boat motor that ran fine.
The problem is the heat acting on the inlet side of the pump. Thirdgens are just too cramped under the hood. Everything under hood get too hot.

paulmoore

Well, I was at work tonight and decided to take a look at the Profilter that is before the pump. I disassembled the filter and to my surprise the filter was clogged with rust. Probalby happened when the vehicle sat for a while with no gas in the tank. Anyway, I took the paper filter element out of the tube and cleaned it and reassembled it without it to mimick a hard line with no obstruction. Engine screams all the way up to redline at WOT with barely a bog/flat spot and without pressure taking a nose dive and the engine falling on its face. So, in this case I think that I am going to get a new filter and plumb it in after the mechanical, and then install the electric fuel pumps so that the inlet line is pressurized and see how that all works. Tomorrow when I get up I am going to take a picture of the filter element so you can see how bad it was. I'm surprised that it flowed anything at all. Once again, i'd like to thank you guys for helping me out.

Sonix

iTrader: (1)

Yea, as soon as I saw your post I thought "whoa, filter *before* a mech pump? uh oh".

Just throw the filter right before the carb like everyone else does. I'm not sure you need to go through the trouble of using electric pumps. You can always add those later if this doesn't work, but don't fix a non-existant problem eh? You'll just need to get a pressure regulator, and buy $$electric pumps$$, and new lines, and....
.
.
Glad it works though! Hopefully that clears up the rest of your problems too! (chances are...)

paulmoore

You guys gave me a few ideas in my other post about fuel starvation at WOT. At first I was going to bypass the Profilter but then I decided that I can take the filter apart to inspect it as well as make it a straight through without the filter element insde. When I pulled apart my Russel Profilter yesterday I saw this...

F-BIRD'88

Thats nasty! Glad to see you found the problem. is the fuel pressure steady now thru all gears WOT?

paulmoore

F-BIRD'88- It stays at about 5 PSI when fully warmed up. It hasnt gone below the 5 PSI at WOT in either 1st or 2nd gear. I can't take WOT at 3rd gear becuase I have a hellacious vibration that starts at about 50 MPH and gets worse as speed increases. When I put the car up in the air to check it out I found out what I had already expected. My 517 ft. lbs of torque BENT my driveshaft. Needless to say I haven't driven it for the last few days as I eagerly await my 3 inch steel driveshaft with heavy duty spicer universal joints from Spohn.

jbenge

iTrader: (2)

Glad to hear you have your problem solved. If you still want to upgrade your fuel system I would suggest going to an electric pump and forget about the mechanical. I'd rather make one major upgrade and spend the money once rather than upgrading several times and redoing things. I'm using a Aeromotive SS pump, its rated to 750HP with a dead head regulator and up to 1000HP with a bypass regulator. I had a sump welded on my stock tank and ran a 8AN braided line to my pump with a metal screen type filter to catch the big stuff before the pump. After the pump I have a Profilter(just like yours) mounted under the car. From the Profilter the line goes to the regulator(Aeromotive bypass return style) and to the carb from there. The return line is a 6AN and I had a fitting welded on top of the fuel tank for it. Its not the cheapest or easiest fuel system upgrade but its a great setup and its been totally trouble free since I installed it a few years ago. I'd rather go overkill on a fuel system rather than have to worry about fuel starvation or it failing and leaving me stranded somewhere.

paulmoore

jbenge- I can agree with that. I think that for now I will drive the car around to try to verify that this thing is actually fixed and won't give me any problems. If for some reason I run in to some issues, then the whole system will get upgraded once and for all....