First Time trial....Fuel pressure went to Zero ran 6.90 @ 100 in the 1/8th and then it died.

Second trial..the same

Dialed a 13.00 in the first round, ran a 13.18 and lost on my street tires..

Hoh humm humm

Tough luck Tom...will you go back manual or switch to electric?

thats crappy, is this your carter that went bad? How much time do you have on this pump?

Yes it is the Carter, This was to be year 4 with it.

I am going to check for blockages somewhere in the system, I have a 12" long -10 BG Filter tucked up under the chassis to check tomorrow.

I have a Brand new Mallory Comp 250 Pump that I was going to use as a test this season. If I don't find a blockage I will probably run the Mallory right away since I am already plumbed and wired for it and see what happens.

The best part about this is that if it turns to definetly be the pump, I was still able to drive home no problem with 7 psi at 70+ mph as a mechanical pump gives you the warning signs before totally going away.

Thats why I have kept my mechanical,,,what does a 172gph Carter cost?

Originally posted by Rapid Robert:
Thats why I have kept my mechanical,,,what does a 172gph Carter cost? They are 75.95 I got mine from Competition Products. Part#M61045

Tom,

Im curious, will you be dead heading the fuel system when you install the 250 and what regulator will you use? I just sent one bsck to Jegs it was spraying fuel like a sprinkler. But I do hear good things about them.

Thanks Rich

I don't think I will be using the 250 pump for a long term solution after reading up on some tech archives from Mallory. They (Mallory) say if you dead-head it it will reduce the life of the pump. and it really should be run with a return regulator using the same line you feed it with. I have -10 line feeding it. I have the 4309 return type regulator already mounted in the engine compartment, but I am not to keen on dropping my fuel tank and installing a -10 return feed bulkhead if I do not need that kind of fuel delivery. Also there is not much room to safely run another -10 line front to back, they are so big.

I am now rethinking maybe a Mallory 140 hooked up to push the (New) Carter I will be ordering tomorrow. I already have a -6 return line plumbed into the tank currently plugged.

Maybe a pump that doesn't require a regulator to turn on with a microswitch when at full throttle.??

Any other suggestions?

You can use a return line that's smaller than the main line. The only thing you are concerned with, is how much pressure it takes to return the fuel through the line. This pressure needs to be less than the pressure you want at the carb. Use gentle bends, and don't use restrictive fittings.

I leanred this the hard way after I installed the return regulator and line for the first time. I couldn't lower the fuel pressure to the 7psi that I wanted. By putting guages all around, I figured out that I had a restriced return line. By reducing the shaprest bends and replacing restrictive fittings, I was able to lower the return resistance to like 5 psi, so now I can set the pressure at 7, and whatever extra gas is flowing up to the regulator now has a clean path back to the tank. FWIW, I use -6
line, for both the main and return, BUT the return line goes back into the tank through one of the small vent ports (1/4 ?) Hehe, I didn't feel like dropping the tank yet either! :D

If you wanted to try the electric, I would try the -6 return that you already have. If you can lower your fuel pressure to where you want it set at, then you are good to go. If the return line is too small or restrictive, you won't be able to set your pressure low enough. It will stay too high, but only up to your pump's max pressure of course!

chris

They (Mallory) say if you dead-head it it will reduce the life of the pump. and it really should be run with a return regulator using the same line you feed it with. Tom, thats not true, the mallory 250 is built with a return port right on the pump. The only way that would be true is if you block the return port with a plug. Then (and only then) will you need a return style regulator

My Chevelle Page (http://home.swbell.net/kenladd/Home.html)

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10.25 1/4 mile @ 130 MPH

Thanks Gateway - That is the way I plumbed the braided line. I have a -6 line as a return line from the pump to the tank. Not sure if this is enough, seems it would be because of such a short distance.

....

This is from Mallory's websites Tech Section..

Question: Brand: Mallory

1. Is your 250 Pump rated for continuous duty (ie street applications)? 2. Is the return/bypass line from the pump to the tank, or from the regulator to the tank? Thanks.

Vehicle/Engine Specs:
Make: Chevy Model: Corvette Year: 67
Engine Type: 548 Transmission: RG 5-sp
Modifications: 11:1 CR 548" BBC pump gas roller engine for street/strip w/ AFR 335 CNC heads. Should make an honest 780 - 800 HP at 6500 rpm
Discussion Topics: fuel

Solution:
The 250 pump can be used in a street application but it works best if a return regulator (such as 4300 or the Mallory return log) is used. A return regulator greatly reduces the load put on the pump. When a return style regulator is used, the return line runs from the regulator back to the tank. The return port on the pump is plugged when a return regulator is used. If you decide to use a dead-head (non-return regulator) such as 4200, the return line runs from the pump to the tank. However, using a dead-head regulator reduces the life of the pump.


10SecBU - Did you ever try to run the 250 using just the return port on the pump?

Tom,

No I did not try using the return line from the pump. I prefered the return regulator to take advantage of the fuel cooling it would see over traveling the length of the car back to the tank.

Also, it is incorrect that you can use a smaller size return line when using the 3 port return style regulator. I know this as my system was originally plumbed with #10 feed and #8 return from the regulator. I could not get the fuel pressure to set below 10-11 lbs. A tech at Mallory brought this to my attention that the fuel was backing up in the return side. I spent the bucks and replaced the #8 return side with #10 and low and behold, I could now adjust the pressure down to the required 7 to 7.5 lbs. My feed & return lines are braided line with very minimal bends. There are two 90 degree hose ends, but each are the full flow which yeild very minimal restriction. Both feed and return shared near identical routing and hose end configurations.

Tom-
Was it the 4601HP that died on you?
http://www.jegs.com/cgi-bin/ncommerce3/ExecMacro/product/item_image.d2w/report?prnbr=180-P4601HP

Originally posted by thrasher:
Tom-
Was it the 4601HP that died on you?
http://www.jegs.com/cgi-bin/ncommerce3/ExecMacro/product/item_image.d2w/report?prnbr=180-P4601HP It was the the Mechanical M61045 (172)

10secBu,
I just want to clarify my statement about the smaller return line. Yes, a bigger return line is better. But having the same size return line as the main, or having a smaller return line will also work - sometimes. It's all about pressure vs flow.

If you had a small low flow pump, you could easily get by with a smaller return line. I have a 72 gph electric pump, -6 main line, and my return line goes through the 1/4" vent hole in my tank. It's smaller than the main line, yet it still works, and allows me to set the pressure down to where I want it at 7psi.

The pressure in the return line is cause by insufficient flow. When you restrict flow, you build pressure. If you have high-flow pump, you will probably need a higher flowing return line to allow you to set the lower pressures you want. If you have a meduim or small flow pump, you won't need to have a super high flow return line. The pump won't flow enough to cause pressure to build in the return line.

If Tom already has a return line in the car, all he has to do is hook up the regulator and pump and see if he can set the pressure down to where he wants it. If he can, then the return line flows enough for his combination to work correctly. If the pressure can't be lowered to the desired setting, then the return line is too restrictive and needs to be bigger, or otherwise less restrictive. (better fittings etc)

Please don't take offence to me restating my point. I design hydraulics for a living and I take some of this stuff for granted, and maybe I didn't explain myself really well. I'm much better at working on stuff than explaining things smile.gif

chris

The only return line I have right now is one that is plumbed to be connected as a pump bypass. It runs to a 3/8 vent tube on the tank to the back bumper area to connect to the pump...I am trying to keep the car as much non-electric as I can.

I have kind of this curse on me concerning electrical items...it must have been passed down to me from a distant ancestor. :confused:

Hehe! So I typed all that junk and you can't even use it? smile.gif Ah well, I tried to be helpful...maybe somebody will learn something.

While you may be cursed by anything electric, I can share your pain. I'm cursed by anything nice. I get new wheels for the car, and lean one up against the wall. 5 seconds after I walk away if falls on its face and gets a few scratches. Got a new car, 2 weeks later there's already a grease stain on the cloth seats from my pants and some kind of gooy road tar on the rocker panels. Got some shiney new valve covers, and I haven't even had them in the garage for 1 minute, and I drop one on the concrete and scratch it. The list goes on.... :mad:

Good luck with your project!

chris

Ahh! Chris, Okay were about equal....

Guys, there is no need to run a return style regulator. In-fact they will cause more problems than they are worth.

The only reason for a return up front (fuel log return or return style reg) is for circle track applications. The purpose is to have a steady flow of fuel during heavy acceleration/de-acceleration. The regulator doesn't have to start/stop the flow like a dead head which can cause problems with recovery under high demands. That's it, fuel is no cooler with either a bypass regulator or bypass pump.

In drag racing, where your at full throttle, the dead head is open for entire run (no need to recover) so there is no need for the return at the regulator

However! you need the bypass at the pump to keep the pump running cool allowing it to run without an excess load (street use)!

I did allot of research on the Mallory 250, both talking to several racers and techs.

IMO, this pump is as good as the BG 400, Holley 350 and others as far as the flow. Plus it's superior when talking service and longevity.

My Chevelle Page (http://home.swbell.net/kenladd/Home.html)

3830 lbs
All Steel with full interior
10.25 1/4 mile @ 130 MPH