Guest zfan Posted March 14, 2002 Share Posted March 14, 2002 Ive currently got a 355 sbc with a 750 double pumper on it. I feed it thru 3/8 line feed by a holley blue pump with regulator. Regulator has fuel pressure gauge and 1/4" return line. I had a edelbrock 750 on it before with pressure set at 5 to 5 1/2 lbs. Now that I installed the holley double pumper I cannot get pressure up past 6 lbs? Should I plug return line and hope it builds enough pressure to get to 7 plus pounds? Tempted to rethink things and go Holley high output mechanical pump. Anyone have this problem? Seems that ever since I swapped to holley double pumper it has been one thing or another Im beginning to miss my Edelbrock 750 simplicity. zfan..Mike Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted March 14, 2002 Share Posted March 14, 2002 6 lbs should be fine..... are you haveing any problems with the carb?? Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 14, 2002 Share Posted March 14, 2002 Grumpy, Yes I am! Cannot seem to get the car to idle below 1000 to 1200 rpm's. If I lower idle it wants to die. Seems very sensitive to lower rpm's. I must say it is very responsive at 2k and up. By the way this is my first trip into double pumper land so Im just feeling my way around for now. I also ordered the holley carb book by Hotrod magazine from Barnes and Noble, should have it in one week. This should help. It is a 8156 750 double pumper, factory deleted idle with four corner idle. Was rebuilt before putting on my car. zfan..Mike Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 14, 2002 Share Posted March 14, 2002 Whoops..Ment factory deleted choke. zfan..Mike Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted March 14, 2002 Share Posted March 14, 2002 sounds like the floats are to high to me, read this, http://www.bob2000.com/carb.htm http://www.shockley.net/holley-jets.asp http://www.bgsoflex.com/holley.html Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 14, 2002 Share Posted March 14, 2002 Thanks alot Grumpy, very informative. I will definetly save the sites you listed above. Thanks again! zfan..Mike Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 14, 2002 Share Posted March 14, 2002 Andrew, Yeah I deserved that one!! Whoa! Factory deleted idle..doh!! Homer Simpson to the rescue! Will look into all facets. May delete fuel return,What exactly did you mean by fresh air vent the tank? Sounds kinda flamable? zfan..Mike Quote Link to comment Share on other sites More sharing options...
Andrew Bayley Posted March 15, 2002 Share Posted March 15, 2002 Mike, Not sure why you're not able to get more than 6psi to the carb. If it was me, I’d scrap the return line and simply run a fresh air vent to the fuel tank. The regulator should be plenty strong enough to hold as low as 3 psi from a 15 psi source. I’ve run my Holley blue at 7 psi for about two years now with a Holley regulator and have never had any problems without a return line. The only reason I could see running a return line, is if you had a variable pressure fuel system (i.e. Fuel injection). Even then, there are many OEM systems that do not use a return line. As for the carb not idling below 1200 rpm, that’s weird. Maybe it’s because you have the ”Factory deleted idle” Sorry, couldn’t resist it. Seriously though, when I first bought my 650 double pumper, the floats would stick open and start pouring gas down the boosters. These things absolutely need to be checked from the factory. After I unstuck the sticking secondary float, I still had some driveability problems. Out of the box, the main float was set almost to the max while the secondary float was cranked all the way to the bottom. It took me a while to figure out why the car would fall on it’s face once I opened her up. Also, check your idle circuits carefully. I wouldn’t even worry about the secondary idle circuits at first. Crank those babies all the way in and start with adjusting your primary circuits first. Once you got a decent idle, then try to adjust the secondary idle screws. Many motors work just fine on primary idle circuits. I was going to drill my carb out for four corner idle, but I didn’t have the room (new casting) so I still only have primary idle circuits with a 500+ lift cam. No problems over here. Once you get the Holley dialed in, you will never go back to “Brand – X”. First time I tore my 650 dp apart I said: “That’s it? It’s a fricking metered gas leak!” Good Luck -Andy Quote Link to comment Share on other sites More sharing options...
Andrew Bayley Posted March 15, 2002 Share Posted March 15, 2002 Nobody seems to have a good explanation on how to do vent lines. I agree, it sounds dangerous, but I know it needs to be done. Picture a half gallon milk jug filled with water. Now turn that upside down (preferably over the sink). Watch the water come pouring out. Also watch the jug crush itself inwards from all the excess vacuum built upside from the lack of an air vent. I’ve seen a lot of people run into fuel pressure problems from lack of an adequate vent line. Car runs great for about ten minutes. But then, all of a sudden, the fuel PSI drops off. I guess the vacuum inside becomes greater than the pressure that the pump can provide. It seems the popular fix a lot of people do is drill small vent holes in the gas cap. Since I’m running a fuel cell with the gas door located in the hatch… this is not an option. I’m going to run a four foot long rubber hose to the old gas door location. There are check valves out there to prevent gas pouring out during a rollover. I want to run one, but am concerned about blowing off pressure build up in the tank on hot summer days. I guess I’d rather have tank pressure on a hot day, than a gas stove underneath me after a roll over. -Andy Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted March 16, 2002 Share Posted March 16, 2002 Noooo! You do NOT want pressure! Trust me, it's as bad as vac. Plastic cells will swell and aluminum cells will oilcan. Vent it so that the tank can breathe. Yeah, sounds bad but it has to be done or you'll regret it one way or another... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 19, 2002 Share Posted March 19, 2002 A return line isn't a bad idea in a street car, even a carbureted one, so I wouldn't necessarily eliminate it.It can help prevent vapor lock. You just need a little more fuel pump, from the way it sounds. There are tons of options on electric pumps, but one of the easiest and least expensive routes for you would be to go to the Holley Black Pump. Its 140GPH (vs 110 or so for the Blue), and it uses the same housing so yo uwon't have to do any major replumbing. Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 22, 2002 Share Posted March 22, 2002 The regulator that comes with the Holley blue pump is not a bypass style regulator. If you hook one side of the regulator to the stock return line you are creating a big leak back to the tank and you may never get the pressure you need consistently. If you want to use the return line, you have to by a carburated bypass style regulator that has a dedicated return port. They are about $75 for the cheapest one I've seen advertised. Quote Link to comment Share on other sites More sharing options...
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