Racin_Jason Posted March 12, 2001 Share Posted March 12, 2001 I've read different specs here and there on the 240's system and Im looking for da facts. What size is the feed line and where is it routed? I've seen mention of return line(s) being stock on these cars?? If so what size are they? Can the stock feed line support a mild 350 with a deadhead regulator? How about alittle more than mild? Are the pickups in the stock tank easily uncovered from hard acceration? Thanks for any help here, jason Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted March 12, 2001 Author Share Posted March 12, 2001 bump Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 12, 2001 Share Posted March 12, 2001 Jason, My set up is a little more than mild therefor I went to 3/8 aluminum line and holley blue street/strip electric pump with fuel pressure regulator. Also used stock fuel return line. Line in my 71 is 5/16 I believe and was ok. Just wanted to be sure so I upgraded. Mike Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted March 12, 2001 Share Posted March 12, 2001 Zfan is correct. The stock line on a 71 is 5/16 and IMO, too small even for the mildest SBC. I am running -8 feed and -6 return to the firewall where it is connected to the original 5/16. From personal experience, if you plan on any hard acceleration , the original tank will have a cavitation problem unless you keep the fuel level high. ------------------ Scottie 71 240GN-Z Scottie's GNZ Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted March 14, 2001 Author Share Posted March 14, 2001 If im reading that right Scottie..you are using the 5/16 as a return line and ran a -08 the whole length for a feed, correct? If i have to run all new lines Im not going to be able to afford braided..and Im not sure I trust aluminum tubing on a car thats so low. What do you guys think? Is there another alternative that is inexpensive and would be safer? I believe the stock line on my Camaro is 3/8 and it fed this 350 just fine. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted March 14, 2001 Share Posted March 14, 2001 What Scottie is saying is use 1/2 inch line (8AN) for the feed and 3/8th line (6AN) for the return. I also highly recommend this. I'm running 8AN all the way up and back and I can't stress enough flow for the pump and the sytem as a whole! Mike ------------------ http://hometown.aol.com/dat74z/myhomepage/auto.html "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted March 15, 2001 Author Share Posted March 15, 2001 Ok I'm going to upgrade the feed to a 3/8's and use the 5/16 as the return..is this ok? Do you have to weld a 3/8 bung or tube into the tank? Also where are the stock lines entering the tank, anyway? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 17, 2001 Share Posted March 17, 2001 I have used 3/8" aluminum on my Z. It is tucked just inside and next to the seam weld lip under the rocker. No chance of scraping anything there (unless it takes the lip completely off. Anyway, I have seen a lot of horsepower fed by a 5/16" line. I cannot see the bowls going dry on anything less than 400hp at constant WOT with a descent push type electric pump at the tank. I remember the factory 5/16" fittings and tubing with mechanical pumps on the engine in the 60's being used on the big blocks. Terry Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted March 17, 2001 Author Share Posted March 17, 2001 Terry, About the 5/16 being used on BB's...the guy I bought this from had a 406 in it that was 12:1 compression and was running a thirsty 750 double pumper! I road in it and it, amazingly enough, flat hauled ass all the way to <cough> 8000 RPM'S! I've been taught that theres really no such thing as overkill in fuel line size, but Im wondering if the general acceptance for what size can supply what power is wrong. In my cars case..I would have never believed THAT engine was being fed by a 5/16 line. Still shocks me when I think about it. But, even more shocking is that he had the shorty headers Y'ing into a SINGLE 2.5" PIPE! I can only imagine how the top would have felt if that was TWO 2.5" pipes. But, it DID still HAUL ASS. Go figure.. Do I HAVE to use a return line with the Datsun fuel system (vacuum issues?)...and if so can I use the feed as the the return? To go 3/8's feed..will I have to weld in a new bung?..please tell me theres an easier way! Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted March 17, 2001 Share Posted March 17, 2001 Jason, what you really need to know is this; Is the stock 5/16" fuel line going to cause enough of a restriction that fuel pressure will drop significantly to the carb (I think you said that you were running a carb) that the bowls would empty before the pump could replenish them. That depends on several factors. Witch is good because then if you do have a problem you can adjust other factors rather than changing your fuel line witch IMO is a big pain. If you don't have a very thirsty motor, if you are not seriously racing, I say try it, use the stock line. If you do fuel starve, change to a stronger pump, much easier then changing a fuel line. This is just my opinion, there are a lot of guys here who are serious racers and have more experience than me. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 18, 2001 Share Posted March 18, 2001 I'm using the stock tank and outlet pipe to a filter and Holley Blue pump near the tank. From there I have a 3/8" AL line up to a Holley regulator on the firewall. Then 3/8" hose to the carb. My theory is that if I get to even 400hp, I should be fine. The Holley Blue pump puts out 14 psi, and flows 70 GPH at 9psi (according to Holley). I only use 6psi, so the actual rate of flow (without flow restriction induced drop) should be higher than 70 GPH. I went this way to never have trouble with fuel flow. But that Blue pump is awful loud, even triple isolated from the car. I'm going to redesign the mount, and use softer rubber. Anyway, my point is, even a 5/16" line, under enough pressure, can handle quite a bit of flow. I don't have the engineering texts here now, but it's not like the 5/16" line becomes a tiny straw. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 18, 2001 Share Posted March 18, 2001 Pete, Amen to the noise on that fuel pump. I have the same pump, and have had it since '85. I always thought that with all that noise going on back there that this thing can't last very long, but it's been the best. I have tried several methods to soften the noise, but it is still louder than the turbo mufflers. At least I know it's working back there without looking at a pressure gauge. Terry Quote Link to comment Share on other sites More sharing options...
Racin_Jason Posted March 18, 2001 Author Share Posted March 18, 2001 Thanks for the input once again. I assumed that the stock line could support a fair amount of power if the pump was strong enough. I would prefer to stay with the mechanical pump thats on the 350 now for simplicity. The aftermarket mechanicals can support a SB well above 350HP I would guess. I suppose I'll just try the stock line to the engine bay at first and if it does starve..i'll do 3/8 line ala' Pete Thanks again Jason Quote Link to comment Share on other sites More sharing options...
John Scott Posted March 18, 2001 Share Posted March 18, 2001 Here's some more info. I've been gathering recently from www.centuryperformance.com/fuel.asp : Minimum line size from pump to regulator for hp, regardless of pump: 250= 5/16 or -4 375= 3/8 or -6 550= 1/2 or -8. Also, with the .5 lb fuel/hp rule, 400 hp= 33 gph. Since fuel pressures are rated in free flowing, you can pretty much disregard a pump's advertised rating for satisfying hp. With a dead head style regulator, not as effecient or precise as a return style, to the carburetor, multiply your max hp 400 x .23= a 91 gph pump. This is the minimum size for 400 hp. With a return style regulator, more effecient, multiply your 400 x .17= 68 gph pump. I don't agree on using a smaller return line than feed line with a return style regulator. A larger or at least same size line allows the pump to run at minimum effort. This is why a return syle regulated pump will outlast the deadhead style, which has to constantly be banging up against the pressurized fuel. Return style regulators keep the pump cooler, run cooler fuel and have more accurate pressure. Pressure is determined by rerouting excess fuel rather than stopping and starting like the dead head. Return line size should be based on pump volume. 45 gph/-4 line, 90gpm/-6, 180 gph/-8. JS [This message has been edited by John Scott (edited March 19, 2001).] Quote Link to comment Share on other sites More sharing options...
Mikelly Posted March 18, 2001 Share Posted March 18, 2001 JS, I agree 100%. I wouldn't recommend using a deadhead style pump, and the return should be the same size. That will allow maximum life from the pump and keep flow where it should be! I'm running -8 line up to the regulator and back from the regulator. I do drop to dual -6 line from the reg. to the carb! Mike Mike ------------------ http://hometown.aol.com/dat74z/myhomepage/auto.html "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
The Rototiller Posted November 5, 2005 Share Posted November 5, 2005 i am going to use the holley red pump (7psi and 97 gph) and run the fuel through the stock 5/16 fuel line to the edelbrock 600cfm carb (no return line needed for carb) the edelbrock istructions say not to exceed 6.5 psi at the carb. i am thinking that i will lose some pressure due to the smaller fuel line but still be close to 6.5 psi. anyone else have an edelbrock carb that can share some info? thanks Quote Link to comment Share on other sites More sharing options...
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