Fuel Pump / Regulator Setup

[71 Nova]

My Camaro has dual Mallory Comp 250 fuel pumps (mounted in the trunk) feeding into a Mallory 4300 5 port return style regulator mounted near the carbs. The pumps have their own internal bypass ports that can be plumbed back to the tank. The instructions say that you can either use the bypass on the pumps (plugging the return port on the reg) or use the return port on the reg (plugging the bypass outlets on the pumps). See the attachment page 2, figures 2 & 3 for the two configurations Mallory Comp 250 Fuel Pump

So the question is: does either of these configurations have an advantage over the other, or are they about the same in practice?

Ken

[John_Heard]

Is this a nitrous car? Or N/A ?

[71 Nova]

It's a nitrous car, but it has a totally separate system (tank thru regulator) mounted up front for the nitrous fuel supply.

[John_Heard]

For just the carb, no I don't think the full bypass is necessary and would be just extra weight and expense.

If you were running both the nitrous and carb on the rear cell, then yes I would suggest it for more stable fuel pressure. Bypass at the rear tends to drop at launch for a little bit.

[71 Nova]

Thanks, John.
The line from the pumps to the reg by the carbs is only 1/2". I'm thinking that 1/2" is too small for 900HP, and that I should go to a 3/4" line (N/A only). What do you think?
Ken

[John_Heard]

Well, if you figure the combined area that the carb inlets have, or your fuel regulator has and how much fuel it can pass, the 1/2" line is probably plenty big. However on the other hand, most people run a -10 line from the back to the front on larger hp setups.

[supernova]

Mine has a an-12 from the tank to the pump, an-10 pump to fuel log, 2 regs on the fuel log 1 for carb and 1 for nitrous, an-8 from reg to carb (line each for front and rear), an-6 for the nitrous. I run 28-30 psi to the fuel log, 7 1/4 psi to carb, and 6-7 1/2 psi to the nitrous noid.

Here's a site that will help with an sizes: http://www.gre6.com/ansize

An-8 is good for up to 700 hp. anything higher you'll have to go up on everything, hose size, fuel pressure, all fuel related items.

[71 Nova]

Thanks guys, good info!