I drew up this diagram on how my fuel systems are plumbed.
The surge tank should remained topped off and airless unless the gas tank is getting low and air is being pumped in. I actually do not know what happens under WOT as the EFI pump and engine consumption starts to exceed the lift pump's ability. What I suspect happens is a vacuum starts being generated in the surge canister, which I expect the first thing to happen is it draws the fuel from the return line back into the surge canister then eventually sucks air from the tank. I also suspect the lift pump starts flowing a bit more as the vacuum starts to build in the surge canister until it sucks air from the return line. Given my pump flow calc's, I assume my setup has never actually pulled air to the surge canister, only perhaps has drawn fuel from the return line because I am rarely at high rpm WOT for more than a few seconds at a time, 13-15 seconds is about it. Also, the lift pumps in my Skylark and I used in the Thunderbird were the stock mechanical pumps attached to the block. The Firebird will have a universal 3/8th electric lift pump.
The surge tank should remained topped off and airless unless the gas tank is getting low and air is being pumped in. I actually do not know what happens under WOT as the EFI pump and engine consumption starts to exceed the lift pump's ability. What I suspect happens is a vacuum starts being generated in the surge canister, which I expect the first thing to happen is it draws the fuel from the return line back into the surge canister then eventually sucks air from the tank. I also suspect the lift pump starts flowing a bit more as the vacuum starts to build in the surge canister until it sucks air from the return line. Given my pump flow calc's, I assume my setup has never actually pulled air to the surge canister, only perhaps has drawn fuel from the return line because I am rarely at high rpm WOT for more than a few seconds at a time, 13-15 seconds is about it. Also, the lift pumps in my Skylark and I used in the Thunderbird were the stock mechanical pumps attached to the block. The Firebird will have a universal 3/8th electric lift pump.
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