I'm using 4 Weber downdraft carbs on my 428 Ford. They want about 4# of pressure at the carbs. I have a speedway 14# electric pump. I have the 3 port regulator. Do I need to use a byp*** line back to the pump? Can I put a weaker spring in the pump to lower the pressure? Thanks for your help.
Those carbs really only want about 2 psi. Maybe 3 max. Should be able to use a two port regulator. Don’t think you need a return.
Keep in mind that using a "dead head" fuel pressure regulator might get you by, but it is always a better situation to use a byp*** regulator (return to the tank) as the pressure delivered to the carbs will be a lot more consistent and stable. If you're setting up the car and fuel system, then plumb it for a return line and set it up accordingly.
Y'all may have had different results, but with the lower pressure carbs I always had trouble with just one regulator. They never seem to dial down enough to really be right for my Strombergs. One day I Figured I'd step them and ran 2 regulators inline. Seems like the first one knocks it down enough for the second one to do its thing. Works like a charm. It's weird.
The return regulator will handle the low pressure high volume fuel requirements of the 428/Webers better than a dead head regulator.
Agree with the others advising for a return line. It’s added work but will help fuel pressure to be more stable. Might make the pump live longer too.
Here is the best way to think about a "dead-head" regulator (which is what about 99% of folks are using) You have a garden hose and to stop the flow, you put your thumb over the end. Then, when you need more water, you take your thumb back off . . . and guess what . . . there is a big surge of initial pressure and volume. This is the situation that happens with a "dead head" regulator (doesn't matter the brand or pressure rating) - it is exactly the same as your garden hose. When the "thumb comes back off" the regulator . . . your carburetor float/inlet sees this sudden surge of volume and pressure - and maybe it can handle it or maybe it can't. Now wouldn't it be a lot better to have a consistent pressure signal to the carburetor . . . that is what a return style of regulator delivers. Hope my ****ogy helps! B&S
After 22 years running a Holley 'black' vane pump ( 14 psi rating) & a Holley deadhead regulator , in 50k miles I have never seen a pressure surge / spike in any way , shape or form . My fuel pressure gauge is mounted behind the scoop so it's very visible . The internal workings/ function of a quality fuel pressure regulator are a bit more precise than a persons thumb . With a Holley red vane pump ( 7 psi rating) I COULD observe a split second pressure DROP every time a needle valve opened . Most of the surge in your garden hose example is from the hose that expands under 50-60 psi line pressure , a well done fuel system uses mostly steel line . To the OP , Holley makes 2 different springs for their common reg , 1-4 psi & 4_9 I believe , you obviously want the low pressure one .
I'm not here to debate what worked for your particular situation - do whatever makes you happy and works for you. My guess is that you run modern Holley style carbs - which can take 7 PSI all day long. Dealing with low-pressure carbs may not be the same as what you're running - so consider that. While I can get away with a lot of pressure variation with any modern 4-barrel, it can be a different animal running carbs that can only take 2 lbs max. Also, most fuel pressure regulators do not handle really low pressures well - so you have that issue to begin with. About the best ones that I have used are 'Malp***i' ones from Europe. The point is that if you are plumbing a fuel system, it is a very good idea to set it up for a return line to the tank - maybe you'll need it, maybe you won't. BUT if you find you need it - it is dang nice to have the line and return circuit in place. Pick your poison . . .
On mechanical fuel injection systems their adjustable pressure check valves are either routed back to the tank or to the inlet side of the pump. Maybe consider looping the electric pump with one of these adjustable type check valves ..... use T fittings on both sides of the pump and then connect the valve in between ensuring the correct flow direction. Below is an ENDERLE valve but any other brand will work too, spring and shim kits are readily available. Set the pressure with a leakdown tester, that's the common method.
You may not need a return line at all - just depends on how well the regulator works and if the carbs are happy. On MFI setups the mechanical pump puts out a LOT more volume than the engine needs - so a huge amount of fuel is circling back to the tank or inlet side of the pump. Also, there are two distinct types of pressure regulators --> dead-head and return style. Typically, the return style models are for very high performance, high horsepower situations - finding low-pressure models can be a bit tough. Again, he may not need it at all - but it is nice to think about when you're plumbing a car, selecting fuel tanks, etc..
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