How Much Air in Looped Return is OK?

[rbrennick]

Probably Fatmobile again;

I have run the last two weeks on diesel only with my kit installed (non-functioning)(Greasel), but no WVO oil yet- mainly to check that my fuel heating system doesn't leak, and to get as much air out of my IP system.
This kit has a valve to run a standard diesel "fuel in- fuel return" to the stock tank and then switch to the "looped" system.
I am getting zero bubbles feeding the IP (which is good), but when I switch to the "looped system." there is a small amount of tiny air bubbles circulating through the pump (which I see in my fuel line feeding the pump); doesn't increase, but they're still there. Car runs fine this way; should I worry, or is this OK?
Has a vacuum guage- pulls about 6+ PSI running return to tank, and 4 PSI when running looped return.
Is this the air from my vacuum hose, or?
Thanks all,
Rich

[Fatmobile]

You should read zero on the vaccum gauge most of the time while the fuel line is looped.
4 means something is restricting the fuel.
These restrictions can draw air out of the fuel. Drawing it into bubbles.
Getting the vacuum down might keep the air bubbles from being visable.

[canman]

how much air is ok??? it all depends on how much cavitation erosion you want in your pump and injectors ... think about it.