Carb fuel systems

[Michael C Henry]

My car has a sumped fuel tank with two carter pumps each w/ its own toggle switch.One usually does it fo street use second was for extreme, 3/8" hose to holley regulater at firewall behind engine. short hose and chrome line all wrapped w/ heatsheilding feeding two 1860 holleys. Lately seems one pump comes up short of keeping up with engine. I ve replaced filters. I belive that the dead ending the pumps has worn them out.I' ve considered a fuel log w/ bypas or restricted return, a bypas regulater, one pump or two. remember its a street driven car that goes hard now and then.Ideas? money is a consideration.More important I only want to do this one time.Opinions are like as#*oles everybody has one.Can't hurt.

[Ron61]

Michaeel,

I have always ran just one fuel pump with no problem. I had a 427 Tunnel Port in my younger days with two big Holly's and the single pump worked fine. Of course my small block I have now gets by great with one pump but I only have a single 850 double pumper on it. I would think that if you are just going to run it mainly on the stret you could set it up to work great on a single pump. I have a friend who has a built 429 with two fours and he is using a single pump. Some of the race guys can give you a better idea of what to do.

Ron

[speed220mph]

Michael, Doesn't matter how many carbs your engine has when choosing fuel-pump requirements. What matters is max power output. For example, a 350hp engine will require 29 gallons per hour at constant full power or 58 gph for 700hp.

Using Holley's red pump as an example, it will flow 97 gph @ 7 psi. the blue pump ups this to 110 gph @ 14 psi. If you have a real "serious" engine and drive it real "serious", one of their two black pumps may be for you. They flow 160 gph and 250 gph, respectively, at 15 psi. Both require 3/8 inch return lines because that's where most of the fuel will be flowing . . . back to the tank.

If it was me, I would install two blue pumps with two pickups, Y out at the engine, feed into one pressure regulator each, then into each carburetor.

For detailed information on pumps and plumbing, check out Holley's web site: http://www.holley.com/HiOctn/TechSer.../FMFPTech.html

Good luck.

[Michael C Henry]

I have two seperate pickups at the tank short 3/8" hoses connecting filters then hose to pumps mounted on either side and slightly ahead of the rear diff .Then lines merge after pumps w/single 3/8" hose up to single Holley regulater.Old hose is hard and going to be replaced more than likely with two 3/8 braided lines Y'd into a single bypass regulater mounted on firewall.
The pumps transmitt noise up through the roll bar.It's noticable when driving.I beleive a single pump that would keep up when pushed would be real noisy and draw more current and needless wear and tear under most normal conditions.I'll more than likely have to remove the tank and have a return installed. New bypass regulater ,"Y", and return would be new in engine compartment.I'd probably replace the 10" hose and keep the insulated line to carbs.Looking at 3/8" or 1/2" lines to reg and 3/8" return. I haven't bought anything yet, still a plan looking at options and makeing a plan so as to complete in a timely and costly maner. I'll spend some money but not stupidly and time is short .
Brands, deals, sources all come into play.

[Mr.Fixit]

Bypass type regulators are better than the regular type Holley gives you with their blue pump. They take some of the strain off the pump in low fuel-demand situations. That said, I have plumbed most cars with a blue pump and it's regulator and they work fine for thousands of miles. Braided stainless hose is still rubber hose and will need replacement. Best to run hardline from the rear to the front using hose for connectioon purposes only, that way there are fewer feet of hose to replace.

[Michael C Henry]

I haven't taken my old pumps apart but intend on doing just that.I'll be looking for something foreign that may have blocked the check valves. It seemed sudden that both pumps running became necessary. Maybe one pump while not running was letting some fuel go back to tank.
What about inline check valves?
What about the return line in tank I remember some discussion a long time ago.I did the search but got tired of unrelated stuff.What bout the return inside the tank /High- low ? swirl? just dump it in what is the current thought?I saw where somebody offered a drawing .