G Gress Posted January 17, 2003 Share Posted January 17, 2003 Paul, no you don't need a return line. Your 6psi pump will just think the surge tank is a carb. Quote Link to comment Share on other sites More sharing options...
PaulR Posted January 18, 2003 Author Share Posted January 18, 2003 I'm in the process of plumbing a Holley Commander 950 into my '71 Z w/ 350 Chevy engine. I am replacing the 4 barrel carb I now have with a TBI unit. The carb is currently fed using a Holley red (6psi) fuel pump mounted near the stock tank. My plan is to mount a surge tank in the engine compartment and use the Holley red pump to feed the surge tank via the stock Z line and then pump out of the surge tank with the high pressure pump to the TBI unit via 3/8 line with a 5/16 return line back to the surge tank. My question is: Do I need to have another return line from the surge tank back to the gas tank? I am guessing that I don't, because the Holley red pump seemed to work fine on the carb without a return line, and worse case it mould pressurize the surge tank to 6 psi. I've also heard that this pump actually likes some back pressure to work against. There is a small (1/4"?) vent line to the engine compartment... maybe I could use that as a return line. Your comments and opinions are, as always, appreciated. BTW, here are a couple of pictures of the surge tank I just made. Any guesses what I made it from?? Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 27, 2004 Share Posted April 27, 2004 Paul, I think your setup sounds like what I've seen suggested on the typical DIY EFI sites. How is the system working? BTW, is that surge tank from a mini-keg? What is that? Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 3, 2004 Share Posted May 3, 2004 Most pumps like to have fuel moving through them for lubrication. I'm not sure if the Holley pumps cares. I know most EFI pumps need that flow for lubrication. If you are idling in traffic, the lift pump (low pressure) will not be moving much fuel. Another nice thing about a return from the surge tank to the main tank is that it always keeps the fuel in the surge tank at least as cool as the fuel in the main tank. Not sure what you made the tank from, but it looks like a great fit. I used the steel 240Z vapor (expansion) tank as a surge tank. So far it's been working fine. Pete Quote Link to comment Share on other sites More sharing options...
brokebolt Posted May 4, 2004 Share Posted May 4, 2004 I was just emulsed in a e-mail session with a guy about this very topic. Here is my $0.02. Fuel return lines are nice becuase they keep a fresh fuel supply at the carb inlets. Yes most fuel pumps are a rotary vien pump design and yes fuel is used to lubricate the viens as they operate. If you dead head the pump than the fuel must release pressure by by-passing the vien. This "can" cause wear and "lead" to premature pump failure. Also if you use a oil cooler and run the fuel through it before the carbs this can cool the fuel before it is feed to the carbs and the unused cooler fuel can return to the tank, helping to keep the tank cooler. While I've mentioned it, Z's are the worst design for gas tank temps, all the engine heat and exhaust pipe heat hits the fuel tank dead on. I like a cool can before the carbs to help combat this, but who drives around with a ice chest full of ice and a aluminium coil running though it anyway. Mike Quote Link to comment Share on other sites More sharing options...
Mikelly Posted May 4, 2004 Share Posted May 4, 2004 Mike AKA BrokenBolt just stole my thunder. Everything he said, including the comment about the crappy design of the Zcar fuel system, is 100% true. You don't want to run a dead head style regulator, and running the system through an inexpensive cooler is IDEAL in dealing with presure spikes, surges, sudden drops (Which can be very common in early Zs) and aids in preventing premature wear on pumps. We HAVE had a lot of pump failures over the years, and Holleys seem to be the favorite "My pump Died on me" pump. But I[ve expereienced it with Mallory and Carter was well. So, my recommendation is get yourself a "GOOD" return style regulator, run a nice return line back to the tank, and use that nice surge tank you welded up as a (LARGE ) vacuum can! Mike Kelly 8) Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted May 7, 2004 Share Posted May 7, 2004 Surge tank looks like a Coleman propane torch tank. Whatever it was, it looks really trick now Mike Quote Link to comment Share on other sites More sharing options...
brokebolt Posted May 8, 2004 Share Posted May 8, 2004 Coleman propane torch tank!!! Thanks, it's been buggin' me for a while now. I knew I'd seen it before. Thanks for the post Mike, no more long night tossing and turning for me. Hey Mike Kelly, thanks for the kind works. Nice to see a Zguy that knows his stuff. Mike Quote Link to comment Share on other sites More sharing options...
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