is it really necessary to prep A carburetor fuel tank for fuel injection?
 

I'm about to do a 13b GSL se swap on my 80. do I really need to take the tank out and install a slosh cup or a surge tank? has anyone ever used the stock tank as is with a fuel injection swap?

Surge tank will do fine. If anyone tell you otherwise, they are full of shit.

I removed the tank, welded the slosh tank in the bottom and welded the fuel pump hangar bolt-in to the tank in place of the stock 12a pickup tube after cutting it out.

I guess I wouldn't try to run EFI without any baffling whatsoever in the tank. Take a left turn too quickly and you'd have a lean burn before you even knew what happened.

I installed a stock S4 NA ECU and engine setup in an 84 GSL. It got an MSD 2225 fuel pump and some EFI rated hose. It works well enough with the stock injectors. That's about it.

How does it handle corners and accel/braking? One time when the owner was accelerating hard with not a lot of gas in the tank, it lost power due to the pickup tube sucking air for a second or two. It doesn't do that with 1/4 tank or more fuel. So don't let the tank get too low.

If the engine had been a T2, it wouldn't have survived.

My advice to the thread starter is you can leave the tank alone for now just to get it running. If corners or fast accel/braking become a problem, you can drop the tank and have a sump cup installed. Also resize the fuel hardlines to what will suit your setup. The stock GSL-SE has a 1/2" send and a 5/16" return. If you'd rather do a blow through carb, I'd still probably do a 1/2" send, but a 3/8" would probably suffice, and as for the return, definitely do a 3/8" return and have it go down into the sump cup like how they did it on the GSL-SE. Why 3/8" return all the way back to the tank? It's what the Mallory 4309 instructions recommend.

The surge tank is basically a mini fuel tank near the pump?

I dont see how a split second without fuel is any worse than a float bowl needle sticking shut and stalling the engine at 75 MPH. I'm just tired of messing with all the little nit picky problems of carburetors. Out of all the second gens Ive had, never have I had a running issue. Maybe an out of adjustment TPS or something easy to fix, but never hard starts and stalling at 75 MPH.

We used a surged tank in my bros RX-2 with T2 semi-pport turbo and RX-3 with 3-rotor turbo. Of course, a pump is needed between the stock tank and surge tank. No fuel starvation at canyon runs.

Any links to finished installs? Could i use the factory pump as the surge supply pump? It only has a few thousand miles on it. Then theres the issue with fuel line. Stock is 5\16" right? SE is 1\2"? Wont the tank still require modification?

I thought the SE's had 3/8" feed line. FC's are 5/16 so I didn't see the need to go any bigger than that for my swaps... As you probably know I went the modded in tank baffle route on my cars, but the surge tank is surely fine as well. The stock pump should be fine to supply it I would think...

Thats the only thing I would be concerned with really. The '80 return line is 1/4". Its kinda small to pass a proper bypass for 30+ psi...

so realistically the best thing that I can do is find a FC fuel tank and chop it up for parts? Cut an opening in the top of my 80 fuel tank and weld in the flange for the in tank FC fuel pump and weld in the FC slosh cup. then I will need to weld the old return line shut and put a breather filter on one remaining line. And the FC fuel pump should work fine for the GSL se engine.

Oh yeah, we never upgraded the fuel return line under the car. It's still the stock 1/4" size but didn't seem to cause any problems as far as I could tell. I think ideally you'd wan't 5/16" like how the factory did it, but it's one of those projects I'd do if the car was already up in the air. Otherwise don't lose sleep over it.

One more thing to add: the owner of the EFI swapped 84 GSL admitted to me that after all the time, effort and money spent on this rather complicated project, he now knows a hogged out Nikki on a 4 port R5 or Y 13B would have been the better choice just due to the elegant simplicity. And you get to see the top of the engine which he kinda misses with all the ugly FC manifolding doing the whole Rube Goldberg thing up there. However one thing he doesn't miss about the Nikki is the cold start up issues which all carbs have. Priorities, right?

This is why they built chokes!

Exactly. I don't see why a choke knob is such a burden to deal with every day. But with that kind of attitude, maybe a stock EFI, with all its limitations, is the best choice for some folks.

It's interesting that there was a steep learning curve to each setup:

EFI had all these wires to deal with such as unwrapping, depinning several unneeded wires from the harness, rewrapping and rerouting the ignition harness through the passenger harness (because the driver's harness is already ocupied in a 1st gen), not to mention finding room to install the large clunky FC coil packs in a chassis that had power steering and kept the battery in the stock location. It also required a custom throttle cable bracket to keep using the carb cable. He also decided to keep the beehive which actually worked out just fine in the end surprisingly, but it create extra complication in that section of the engine bay, as you can imagine. And of course the fuel pump and the wiring to it had to be changed. In the end, the time, effort, well the entire project turned out to be less powerful than what I built for my car.

I did a hogged Nikki which required its own steep learning curve as you can read on this forum in posts by me and tg_farrel. Let's just say there were some growing pains involved. However they were just in figuring out which slow air bleeds to use when you enlarge the venturis as much as we did. There wasn't any direct info on the forum specifically about tuning once the well documented venturi work was complete, other than what Sterling slightly hinted at (nickel plated 60s moved to the primary side), so we had to basically guess. In the end it only took about a month to figure out the right sizes and combinations of drilled and stock air bleeds and fuel jets to get a fantastic running NA-tuned Nikki on the test engine which turned out more powerful for seemingly less work than the EFI setup above. And it was repeatable. Oh and I added a choke cable to my GSL-SE so I could use the fast idle linkage. ;) The choke flap valve of course was removed but with all the mods to the accel pump and properly calibrated idle circuit, it starts easily every time. You just have to keep it running with your foot for the first 30 seconds, then pull the knob to get a good fast idle speed to keep it running while it begins to warm up. A little more hands-on than EFI which is how I like it.

You can swap carbs in just a few minutes. :) You can't swap injectors in just a few minutes, unless you're j9fd3s.

Why are you guys using crappy old FC EFI systems? I can see why someone would have the opinion that it's not worth the trouble over a carb after going through all the hassle to install a 40 year old EFI system. The FC system, as mentioned, was very Rube Goldberg with multiple idle valves, a mechanical throttle nudging system, a bazillion solenoids, multiple temperature sensors, etc. Does it work? Sure? Does it work better than a carburetor? Absolutely! Does that make it a worthwhile candidate to swap into a carburetted car? Uh...not so much.

Why not use a standalone system which does away with all that crazy legacy FC stuff? Run your choice of modern idle valve (or FC), your choice of coils (or FC...which incidentally fit 1st gens very well if mounted under the cowl with the wiper stuff), your choice of trigger (or FC CAS, which drops in place of the dizzy), your choice of modern injectors, etc. etc. Plus features like I/O to run devices like fans, wideband closed loop/auto tune, fully adjustable timing/split, modern sensors, brand new simplified wiring harness, and all that good stuff. At the most basic a 4 barrel throttle body can be adapted, and injectors added to the manifold. Or use (gag) TBI.

Now the main reason I am replying is to show what I did to convert my Cosmo carb fuel tank to EFI. I made a fuel pump hanger and then an inner clamp ring to secure it to the tank via a hole cut out with a hole saw. I was lucky that the Cosmo tank had a small baffled section in the corner which was perfect to mount the pump. I don't think the 1st gen has a similar area but with far more area on the top of the 1st gen tank available to cut a gaping hole, one could integrate a small baffle cylinder onto the pump hanger. Much like almost all modern vehicles do. In fact, companies like Racetronix sell Covette/Camaro/generic fuel pump assemblies with baffle which might fit quite well if I am picturing 1st gen tanks properly.