I put a Holley Street Avenger on my new build and put a fuel pressure gauge inline. When the engine is running, the needle is bouncing wildly between 2 and 12 psi all the time. I get the feeling it is because the pulses from the fuel pump are putting pressure into the line, but the return is letting it bleed of as soon as the diaphram releases for the next cycle. I don't know what effect this is having on the carburetor.

I'm replacing the chrome hard lines with new braided AN lines, a new gauge and was thinking about putting a regulator inline after the filter. Should I also get rid of the return line or is there something else I can do to allow a smoother, more consistent flow to the carburetor. I don't have a problem going with an electric setup with a regulator, but again, don't know the consequences of not having a return line. Here is how I'm set up now.

 

I had the same problem and eventually the guage was toasted by the pulsation. I just ditched the dual feed line and replaced with one that didn't have a guage.

 

When my 76 had a new engine and fuel system put in by a company in Denver CO they opted not to use return fuel line and just blocked it off completely at the tank. I have had no problems since I got the car.

 

I don't have a return line and I have never had good luck with the liquid gauges on the feed lines. They always work for the first 3-5 minutes until the engine starts to warm... then they bounce everywhere like you describe. One speed shop told me it's just the way the guages are - can't handle the temperature under the hood. I just use it to make sure I have initial fuel pressure, after that it is worthless.

 

So, even with the return out of the picture, it still bounced?

 

Still bounced, but it works for about 5 minutes. Seems the heat effects the gauge.

 

Iv'e used regulators and electric pmps but now just use a mechanical and recirc all the way from the carb w/o regulator - installed a .040" orifice to limit flow. Heck some guys just use a 3 way plastic/metal fuel filter for a recirc but that must flow like a fire hose and make tons of vapor in the fuel tank where it dumps.
Yep the mechanicals have an internal regulator and my Carter street pmp is just fine at 6-9psi. What happen when any pmp is dead headed w/o recirc and the carb needle shuts is press increases until something gives - pmp internal recirc opens, carb inlet needle forced off seat. Have used regulators without recirc but now realize mech pmp is self-regulating and an in-line regulator only adds restriction and not needed with a street mech pmp. A hi-press electric would need a regulator though.

If u choose to recirc try a .025" to .050" orifice in the recirc line to limit the flow but smooth out the press.

1 more thing is i added a Holley electric press guage (only $75 - try Jeg's) and the gauge is now in my clock how so i can read my fuel inlet press (right at the needle) from the drivers seat.
Thoose tiny liquid filled fuel press gauges are junk and as the liquid inside heats the operating tube is forced out of calibration. If u want a tiny gauge in the engine compt then use a dry gauge (or dump out the silicone liguid) and average the needle readings as it bounces all over the place. Well it may not if a recirc with orifice is installed to smooth out the pmp stroke pulses. So hey, if u try this give us a post to report how it works.

Hope this helps ya. cardo0

 

Using the clock hole for a fuel pressure gauge (or vacuum gauge or voltmeter) is a good idea-- I'll think about doing something like that instead of replacing the non-functioning clock.