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Mallory 250 fuel pump #692561 05/08/10 07:24 PM 05/08/10 07:24 PM
Joined: Apr 2007 Posts: 325 Greenville, WI B Big B OP enthusiast
Big B OP enthusiast B Joined: Apr 2007 Posts: 325 Greenville, WI	I have a Mallory 250 pump with a return style regulator. I have to set my fuel psi really high(9psi) just to compensate for fuel psi drop on launch. In 1st it drops to 5psi, 2nd 6psi, then in 3rd it recovers to 7psi. This is on a 730hp 493. Is this pump not putting out enough psi to compensate for the g's on launch? How much is this effecting my a/f ratio? Im thinking about ditching this pump and getting a Product Engineering 460.

Re: Mallory 250 fuel pump [Re: Big B] #692562 05/08/10 07:29 PM 05/08/10 07:29 PM
Joined: Nov 2003 Posts: 6,293 Rock Springs Bob_Coomer master
Bob_Coomer master Joined: Nov 2003 Posts: 6,293 Rock Springs	Ditch the return style regulator. The pump has its own return port, just return it back to the fuel cell and dead head the fuel pressure to the regulator. I have run 1 second flat 60ft with that pump making 850 ish HP in a digger and never once had a problem. Best electric fuel pump I have had to date. [color:"red"]65 Hemi Belvedere coming soon [/color] [color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]

Re: Mallory 250 fuel pump [Re: Bob_Coomer] #692563 05/08/10 07:34 PM 05/08/10 07:34 PM
Joined: Apr 2007 Posts: 325 Greenville, WI B Big B OP enthusiast
Big B OP enthusiast B Joined: Apr 2007 Posts: 325 Greenville, WI	I read that return style rgulators are supposed to work better then dead head as far as fuel psi drop. Plus the pump runs cooler. My car is mostly street driven(3000mi/year), so I would like to stick with the return style regulator. If this doesnt effect my a/f ratio I can live with it.

Re: Mallory 250 fuel pump [Re: Big B] #692564 05/08/10 07:46 PM 05/08/10 07:46 PM
Joined: Nov 2003 Posts: 6,293 Rock Springs Bob_Coomer master
Bob_Coomer master Joined: Nov 2003 Posts: 6,293 Rock Springs	Looks like they recommend running the return from the pump to the cell. Im just saying thats the way I ran it, and never had a problem with YEARS of operation. http://www.malloryperformance.com/pdf/5250_5250A.pdf [color:"red"]65 Hemi Belvedere coming soon [/color] [color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]

Re: Mallory 250 fuel pump [Re: Bob_Coomer] #692565 05/08/10 07:58 PM 05/08/10 07:58 PM
Joined: Jan 2003 Posts: 32,394 Q Quicktree I Win
Quicktree I Win Q Joined: Jan 2003 Posts: 32,394	check the back pressure on the return line. you may have some restrictions. sorry Bob the internal regulator is no match for a good return system. PM RobbMc on the board he can get you straight and tell you how to test the system. something is wrong if the mallory 250 wont handle that with ease.

Re: Mallory 250 fuel pump [Re: Quicktree] #692566 05/08/10 08:00 PM 05/08/10 08:00 PM
Joined: Jan 2003 Posts: 32,394 Q Quicktree I Win
Quicktree I Win Q Joined: Jan 2003 Posts: 32,394	also running 9 pouds is not uncommon.

Re: Mallory 250 fuel pump [Re: Big B] #692567 05/08/10 08:52 PM 05/08/10 08:52 PM
Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey J jamesc master
jamesc master J Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey	there's nothing wrong with that pump or the return regulator. i'm assuming you set the pump up to be run with a return regulator and aren't using the bypass port off the pump itself? if by some chance you are using the return off the pump then that is your problem. iirc that pump as it's shipped has the internal regulator set to around 15#. i run it with a dead head regulator on the sig car but a return style regulator is the preferred method. i know many people go ga ga over monster shiney expensive pumps but imho the comp 250 is a nice pump and properly setup is fine for your application.

Re: Mallory 250 fuel pump [Re: Quicktree] #692568 05/08/10 11:05 PM 05/08/10 11:05 PM
Joined: Apr 2007 Posts: 325 Greenville, WI B Big B OP enthusiast
Big B OP enthusiast B Joined: Apr 2007 Posts: 325 Greenville, WI	Don't Holley carbs have needle and seat problems over 8psi? I notice that when I lower the psi to 7psi the engine idle much better. At 9psi I think I am pushing fuel past the seat causing the engine to idle richer. I have the Mallory fuel log and a -12 return line, so I definitely don't have a restrictoin in the return line. It seem to work fine. It's been doing this for 8 years.

Re: Mallory 250 fuel pump [Re: Big B] #692569 05/08/10 11:57 PM 05/08/10 11:57 PM
Joined: Oct 2004 Posts: 8,165 Left Coast B BobR master
BobR master B Joined: Oct 2004 Posts: 8,165 Left Coast	Quote: I have a Mallory 250 pump with a return style regulator. I have to set my fuel psi really high(9psi) just to compensate for fuel psi drop on launch. In 1st it drops to 5psi, 2nd 6psi, then in 3rd it recovers to 7psi. This is on a 730hp 493. Is this pump not putting out enough psi to compensate for the g's on launch? How much is this effecting my a/f ratio? Im thinking about ditching this pump and getting a Product Engineering 460. The pressures you have listed are adequate. Do nothing.

Re: Mallory 250 fuel pump [Re: Big B] #692570 05/09/10 05:45 AM 05/09/10 05:45 AM
Joined: Jan 2003 Posts: 32,394 Q Quicktree I Win
Quicktree I Win Q Joined: Jan 2003 Posts: 32,394	Quote: Don't Holley carbs have needle and seat problems over 8psi? I notice that when I lower the psi to 7psi the engine idle much better. At 9psi I think I am pushing fuel past the seat causing the engine to idle richer. I have the Mallory fuel log and a -12 return line, so I definitely don't have a restrictoin in the return line. It seem to work fine. It's been doing this for 8 years. I know quite a few people running 9 pounds and over. mine is set at a little over 9. -12 is good but do you have a bunch of 90s or bends? go to RobbMc's web site he may have the info to check the system.thats what you need to do and stop all the guess work. or PM him he was an engineer at mallory.

Re: Mallory 250 fuel pump [Re: Big B] #692571 05/09/10 01:36 PM 05/09/10 01:36 PM
Joined: Jan 2003 Posts: 961 Carson City, Nevada RobbMc super stock
RobbMc super stock Joined: Jan 2003 Posts: 961 Carson City, Nevada	The pressure drop you are seeing isn't really that bad but if you want to reduce it, check the following: Since you are using a return regulator, make sure you are not using the return at the pump. It should be plugged. Which return regulator? If you are using the small Mallory (4309), you might not be able to improve things as the 4309 is really a little small for the 250 pump. With the engine off, turn on the pump, Back the regulator off all the way. You should be able to adjust the pressure to less than 3 psi (lower is better). If you can't get the pressure to adjust to less than 3 psi, you have too much resistance in the return line and/or the regulator is too small. Designing a better mouse trap always seems to lead to the evolution of smarter mice. www.robbmcperformance.com

Re: Mallory 250 fuel pump [Re: Big B] #692572 05/09/10 08:43 PM 05/09/10 08:43 PM
Joined: May 2008 Posts: 5,399 Aurora, Colorado 451Mopar master
451Mopar master Joined: May 2008 Posts: 5,399 Aurora, Colorado	Quote: I have a Mallory 250 pump with a return style regulator. I have to set my fuel psi really high(9psi) just to compensate for fuel psi drop on launch. In 1st it drops to 5psi, 2nd 6psi, then in 3rd it recovers to 7psi. This is on a 730hp 493. Is this pump not putting out enough psi to compensate for the g's on launch? How much is this effecting my a/f ratio? Im thinking about ditching this pump and getting a Product Engineering 460. Just to clear my confusion, when you say "with return style regulator" are you referring to the pumps internal regulator or a separate bypass regulator mounted near the carb? I have the Mallory 250 pump, and it puts out a good 15-16 psi to my bypass regulator mounted on the intake manifold where the regulator reduces the pressure to the carb to 7psi. Also, what is the inlet side of the pumps setup? What level in relation to the tank / fuel cell? Is the Inlet -8 AN or larger? Do you have a filter before the pump, and how restrictive is it if you do?

Re: Mallory 250 fuel pump [Re: 451Mopar] #692573 05/09/10 09:40 PM 05/09/10 09:40 PM
Joined: Apr 2007 Posts: 325 Greenville, WI B Big B OP enthusiast
Big B OP enthusiast B Joined: Apr 2007 Posts: 325 Greenville, WI	I have the Mallory 4302M fuel log with bypass regulator built in. Supposed to be good to 300gph. My fuel pump is located behind and below the tank with a -12 line going through a BG5000 fuel filter to the pump. A -10 to the regulator and a -12 back to the fuel cell. The fuel cell has foam in it. Not sure if that will cause a problem. It doesn't sound like it's that big a deal. In 2 years I'm switching to fuel injection anyways

Re: Mallory 250 fuel pump [Re: Big B] #692574 05/10/10 06:35 PM 05/10/10 06:35 PM
Joined: May 2008 Posts: 5,399 Aurora, Colorado 451Mopar master
451Mopar master Joined: May 2008 Posts: 5,399 Aurora, Colorado	Quote: I have the Mallory 4302M fuel log with bypass regulator built in. Supposed to be good to 300gph. My fuel pump is located behind and below the tank with a -12 line going through a BG5000 fuel filter to the pump. A -10 to the regulator and a -12 back to the fuel cell. The fuel cell has foam in it. Not sure if that will cause a problem. It doesn't sound like it's that big a deal. In 2 years I'm switching to fuel injection anyways That is some huge lines. The Mallory 250 pump I have was only sized for -8 fittings?

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