Now that my LS swap is finally on the road, I'm noticing some of the quirks and things that aren't entirely working 100% - one of the biggest being the fuel system. Fueling works great...when I have a full tank of gas. But as I drive the car, things start to get weird.

The car is an '81, it has the original gas tank, and I installed '82 style sending unit from Amazon - and the main issue I think I'm having is fuel starvation. When fuel gets lower, the car acts funky; it bucks as gas sloshes around in the tank, power drops out under hard launches, and starting can be something of a problem sometimes (this is partially due to not being tuned for enough fuel during cold start). Additionally, the fuel gauge displays the wrong level. I'm using Holley's 6.86" Pro Dash and I haven't been able to dial in the ohms correctly, so that's part of the problem - but it also seems to be running low on fuel when it appears to be well above 1/4 of a tank.

My suspicion is the fuel pickup is not long enough, or not angled correctly, and the fuel pump is not getting low enough in the tank. I figured I could correct for this by increasing where the dash thinks "empty" is, but it's not really working out like I'd hoped.

Any ideas/recommendations here? I know Holley makes a drop in EFI sending unit for the C3 that self-regulates and all, but I already have a "functioning" fuel system and I'd hate to rip it all out. Also, it's a bit more than I'd like to spend right now.

 

The Holley drop-in solution (which I also don't like, because it removes the external regulator and return line), comes with Holley HydraMat.

They certainly are proud of that stuff, but it really works, and is available separately.

It also acts as a filter, for better or worse, likely a finer filter than any you would put downstream.

 

Here’s a thread that talks about EFI fuel tanks that also mentions baffling that helps reduce sloshing at lower fuel levels.

 

rabinaba
As ridiculously expensive as it is you probably oughta just try the HYDRAMAT. Would probably address all of your issues.

I modified an 82 fuel sending unit/hanger and installed a CANNISTER EFI pump and I can suck my tank dry..... however if you already have yours all set up then the hydramat may be the easiest path. see attached link. Supposedly hydramat has a GREAT reputation.

Personally I would use modify/fabricate a cannister pump assembly to use with the 82 hanger but the hydramat would be easier. Mostly because I can do it and those hydramats just seem way TOO expensive for what they are.

https://www.holley.com/products/fuel...mat/hydramats/

 

the advantage of EFI tanks is the internal baffles and prevents fuel starvation while driving.

 

Hydramat here too on my 82 LS swap. In stock form the engine would starve in sharp right turns with under 1/4 tank.

No issues at all with the hydramat and I drive it MUCH harder now.

 

My LS Swap is a Turbo 6.0. Since the acceleration is much higher, I went with a separate surge tank instead of a sump or Hyrdromat. It uses a small helper pump to keep it topped off at all times.

This is not the one I use, but just an example.

Another Example

 

I haven't looked into it but maybe a Tank's Inc EFI tank? They are baffled for EFI and typically use a Walbro 255 or 340 fuel pump depending on the hp of the engine.
I've used two of them for LS swaps and they worked perfect.

 

You wouldn't happen to have photos of what you did, would you? Would love to see so I can decide if I should modify or go with the Hydromat.