2 fuel lines to carbs, more fuel pump, regulator, plumbing Qs Options

[brant]

... I'm using option B now, but with no regulator. My fuel pressure guage verifies this is working...

Option B would be easier ... but I don't get it. The fuel free flows right back into the tank... there is nothing to build pressure against.

Is the return line considerably smaller than the supply side?

fuel injection is highly effected by fuel pressure
carbs are not. The only reason for regulation is to now blow open the seats
since they have their own bowls, all the fuel has to do is flow into and fill the bowls.
(think of the bowls as mini reservoirs)

with hydraulics you have to remember that pressure equalizes (a smaller return would effect volume more than pressure). So the bowls fill, and the extra runs back to the tank/cell

I've got a fuel guage near the carbs showing that I'm getting 3.5 to the carbs... the pressure on return isn't important.

the real reason for a return line in a carbed system is to just keep the fuel moving (not heating up while it waits to enter the carbs and sits over the engine soaking up heat) and thus cooler = more hp

option E is actually what the factory used on the 4's, Djet and is good for a fuel injection system where you want to build back pressure. I've used this on carbs also with good effect. I've got one (street) car right now with option E.

also as a side note. I measured output on 4 different used pumps and found 4 different outputs. (3 were facet spares I had) Thats the main reason I used a regulator with the facets... variability. Also the reason I switched pumps in my recent new plumbing job. (plus I saved weight)

[zeezee]

Finally have this in place (option B ).

Several PO plumbing problems were cleaned up. The old facet was mounted so high it would run dry around half a tank.

Other than that there are no drastic improvements. The engine still runs - that's always a plus.

But I'm still not happy.

The replacement pump (CBPerformance Rotory - Carter P60504) is so loud I can hear it over the engine!

I've encased the pump in sound proofing and used rubber mounts. The sound is now tolerable - but not really an acceptable long term setup.

I guess I'll try a Mallory 4070LP - that's supposed to be "quiet".

Also tried a Facet Posi-flo (advertised as quiet) - I nearly had a heart attack when it powered up, it was so loud!

Lots of $$ getting tied up in fuel pumps here.

[rhodyguy]

i can't figure out how you can hear the pump running over the engine. where did you mount the pump?

k

[biosurfer1]

Thats what I'm wondering too...my buddy Justin has the same pump mounted up front and you can barely hear it with the engine off

[zeezee]

Mounted to the lower part of the firewall on the passenger side.
Physically it fits well and makes the hose runs tidy.
In retrospect - not the best place for sounds issues - since it makes the whole firewall resonate with sound.

I don't really see any other place to mount it back there.

I changed the mounting insulators and it's much better.