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hi guys, after melting a few elctrodes on the plugs at the last race using some NOS, I realized it's time to add an additional fuel pump. I run a Mallory 140 and I am adding a seond one, one pump will be dedicated to the motor and one pump with a toggle switch will be turned on when I run the nitrious.
I have a lot of fuel line as well as a return line. here is my question : The return line is the same diameter as my fuel line, I have been told that the return must be larger than the fuel line. How crucial is that and can I get away with using the line I have rather than purchasing larger line ?

Are you adding a second Mallory 140 pump? If so i don't remember it having a return on the pump.Or are you returning the fuel from the regulator? Here is a link to fuel system setup and the returns are not bigger than the feed line http://www.productengr.com/mm5/pumpinst ... nguide.htm

I see no reason to have the return line larger than the feed line.

EDB

Hi Rock and Eric, thanks for getting back to me. Here's what I have :
The motor makes 609 h.p. on the dyno and the NOS kit is at 250 h.p. which I hardly use. But at the track I have my fuel pressure set at 7-8 and by the 1000 ft. mark its dropping to ONLY 1 !! I currently run a mallory 140 ( dead-headed) no return line. We just added the second Mallory 140 yesterday and will finish plumbing the line today. I wasnt sure if it was o.k. to run both pumps to the regulator then to the carb and NOS plate with or without running a return line. Lots of my friends run dual 140's without a return line, I thought a return line would keep the fuel cooler.

i would run the second pump just to the nitrous system with its own regulator
make sure when you set the fuel pressure for the nitrous it is flowing

Yep, what Rock said... /\

EDB

o.k. thanks guys, appreciate it.