Fuel volume drop after regulator?

Doug Domm · 07-04-2011, 11:31 AM

I did the timed fuel test and found 1 gal. @ 32 seconds at the regulator and a tick over 50 seconds at the carb. Agreed this is not adequate for at carb volume. My question is. What is acceptable volume drop after the regulator at the carb? This is with a holley blue pump and holley regulator. Yeah I know time to update! The application here is SBC stocker with Qjet.

Kenny Wigington · 07-04-2011, 04:23 PM

25 or less, Doug. I had a Holley black pump and it would not have enough volume, to keep a quadrajet full, especially at launch. I switched to a Magnafuel 275 and reg., and it made a big difference. Dont use a small fuel pressure guage, a full sized one will be more honest. Run at least a -8 or even a -10 line.

Daran Summerton · 07-04-2011, 06:50 PM

I too just had a blue pump crap out and just replaced it with another blue pump. All the while I was jerking around with it I could not help but wonder is this really worth it vs. a nice mechanical pump??? Really, how much ET could I possibly lose given the GPM was adequate with a mechanical and 1/2 alum. line and get rid of all the braided crap. My guess is not enough to offset the 1000$ in a fuel system.

Adger Smith · 07-04-2011, 07:44 PM

Those Holley Regulators are a joke.
Less than a .250 hole with a .090 pin passing through the hole... not near enough area to pass a decent volume of fuel. I would bet the area of the jets in you Q-Jet are more than twice the actual area available in those Holley Regs...Size the line based on N/S volume and Regulator volume.
OH! did you notice those nice big fittings on that blue pump and that little feed hole inside....never measured one, all it took was a look, but 1/4 in might be near the size...

Mike Pearson · 07-05-2011, 12:25 PM

The holley pumps have been real reliable over the years in my car. You will need 2 of them to supply enough fuel for a Q-jet. I run 2 holley blue pumps and an Aerospace 2 port regulator. I will replace this system with a single Aeromotive, Magnafuel or similar pump when needed.

BobUnkefer · 07-05-2011, 01:36 PM

For What It's Worth.....

Just replaced the fuel system on my D/SA with a complete Aeromotive system and found a .10 of a second that had been hiding. Most noticably in the back half, car now pulls HARD the last 660.
I replaced an OLD (antique?) Mallory pump & regulator and the 1/2" lines the fuel was running through. I now have 2 -8 lines running from the cell to the pump, with a -10 line running forward to the regulator & then the carb.
Even got a call from Aeromotive about a month after the installation asking me to send the regulator back because there MIGHT be a problem with it, swapped it out @ no charge.
Still tinkering with it, heck, there might be some more...... From what I've learned, that Q-jet needs alot of fuel getting to it.

Quality products, GREAT customer service!

Unk

07-04-2011, 11:31 AM	#1
Doug Domm Member Join Date: Apr 2006 Location: canada Posts: 251 Likes: 29 Liked 84 Times in 21 Posts	Fuel volume drop after regulator? I did the timed fuel test and found 1 gal. @ 32 seconds at the regulator and a tick over 50 seconds at the carb. Agreed this is not adequate for at carb volume. My question is. What is acceptable volume drop after the regulator at the carb? This is with a holley blue pump and holley regulator. Yeah I know time to update! The application here is SBC stocker with Qjet.

07-04-2011, 04:23 PM	#2
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Re: Fuel volume drop after regulator? 25 or less, Doug. I had a Holley black pump and it would not have enough volume, to keep a quadrajet full, especially at launch. I switched to a Magnafuel 275 and reg., and it made a big difference. Dont use a small fuel pressure guage, a full sized one will be more honest. Run at least a -8 or even a -10 line. __________________ 2894 STK

07-04-2011, 06:50 PM	#3
Daran Summerton Senior Member Join Date: Jun 2003 Location: Las Vegas nv Posts: 600 Likes: 18 Liked 66 Times in 37 Posts	Re: Fuel volume drop after regulator? I too just had a blue pump crap out and just replaced it with another blue pump. All the while I was jerking around with it I could not help but wonder is this really worth it vs. a nice mechanical pump??? Really, how much ET could I possibly lose given the GPM was adequate with a mechanical and 1/2 alum. line and get rid of all the braided crap. My guess is not enough to offset the 1000$ in a fuel system. __________________ 72 cutlass

07-04-2011, 07:44 PM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Fuel volume drop after regulator? Those Holley Regulators are a joke. Less than a .250 hole with a .090 pin passing through the hole... not near enough area to pass a decent volume of fuel. I would bet the area of the jets in you Q-Jet are more than twice the actual area available in those Holley Regs...Size the line based on N/S volume and Regulator volume. OH! did you notice those nice big fittings on that blue pump and that little feed hole inside....never measured one, all it took was a look, but 1/4 in might be near the size... __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-04-2011 at 07:46 PM. Reason: sp

07-05-2011, 12:25 PM	#5
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,451 Likes: 615 Liked 1,934 Times in 581 Posts	Re: Fuel volume drop after regulator? The holley pumps have been real reliable over the years in my car. You will need 2 of them to supply enough fuel for a Q-jet. I run 2 holley blue pumps and an Aerospace 2 port regulator. I will replace this system with a single Aeromotive, Magnafuel or similar pump when needed. __________________ Mike Pearson 2485 SS

07-05-2011, 01:36 PM	#6
BobUnkefer Member Join Date: Jan 2006 Location: Kansas City, MO Posts: 465 Likes: 0 Liked 0 Times in 0 Posts	Re: Fuel volume drop after regulator? For What It's Worth..... Just replaced the fuel system on my D/SA with a complete Aeromotive system and found a .10 of a second that had been hiding. Most noticably in the back half, car now pulls HARD the last 660. I replaced an OLD (antique?) Mallory pump & regulator and the 1/2" lines the fuel was running through. I now have 2 -8 lines running from the cell to the pump, with a -10 line running forward to the regulator & then the carb. Even got a call from Aeromotive about a month after the installation asking me to send the regulator back because there MIGHT be a problem with it, swapped it out @ no charge. Still tinkering with it, heck, there might be some more...... From what I've learned, that Q-jet needs alot of fuel getting to it. Quality products, GREAT customer service! Unk __________________ Bob Unkefer 4409 STK