The 75TS tank also has baffle plates inside to act as a kind of surge tank.
I thought I needed to do this mod for my Standard GTV tank too, but If I understand correctly, you haven’t done any mods at all?? And you have no problems .... hmmmm maybe I’m being a little over the top then.
Do you have any issues if the tank runs low? Does it still work ok? Do you throw the car around corners much?
I was told, just the slightest air in the line and the EFI shuts the system down.
Do the Commodors have an initial take up pump in the tank?
Once the tank gets below half in my '81 I take it a bit easy (by my standards!) just due to paranoia, but it hasn't given me any troubles yet. Like I say, I intend to fit a surge tank for track duties, but for road use it should be fine - I tend to reckon running the tank too far below half is a bit dodgy anyway, as you start to pick up more nastys floating around in there. My range rover suffers from extreme bodyroll however, as well as pretty serious angles when offroad, and hasn't missed a beat in the 2 years I've been running the secondhand Bosch 070 with an unbaffled tank and no surge tanks or lift pumps. If it dies, I'll probably fit a surge tank to that too, but not until then.
I wouldn't screw around too much with welding the tank, when you can pick up a surge tank for around $100, and then grab a low pressure electric pump to feed it (any carby cars electric pump should be sufficient, really). One thing to note though - I've used the standard carby pickup and sender in mine, feeding the Bosch 070 directly, which gives you your outlet - the problem is the return. Not sure if your GTV has the charcoal canister behind the rear seat on the parcel shelf, but mine does, and originally I just T-ed my return line into the vent line off the filler neck. This worked fine, except for the fact that it filled up the whole vapour system, and I had fuel pouring out at the engine bay! The solution was to plumb the return into the existing fitting on the filler neck, and then drill + tap a new hole about 3-4 inches further up the filler neck to plumb the vapour line to (you can actually see the fitting when you take the filler cap off!)
Incidentally, given your concern about putting a fuel tank in the boot:
a) GTV6s still have a boot mount battery with their boot mount fuel tanks, not only that but the battery is mounted at a lower level than the tank, so if it leaked the battery would float!
b) If your GTV does have the vapour canister on the parcel shelf, you already have a fairly crappy looking 25 year old bit of fuel hose running within a foot of your battery, and even if you don't, the filler neck runs a couple of inches away from it....
Personally I don't get why so many people are really scared of having their battery and fuel tank in the same place - to be as simple about it as I can, read the top of your battery. If its a standard lead acid battery, it will have a warning to the effect that charging batteries emit hydrogen gas, and to keep them away from sparks and naked flames. This should quell any concerns about putting a fuel tank in the same place - after all, if the battery itself releases flammable gases and vapours, then it would be a little ridiculous to fit them in close proximity to people if they are going to arc out and blow themselves up, wouldn't it?
Obviously if the battery comes out of its clamp, and the positive terminal strikes unpainted bodywork or metal that is connected in some way to the negative terminal, then yes you will get spark. Note that your battery label will also warn against short circuiting - spark may equal exploding hydrogen. In my opinion, if it worries you, install a STRONG battery clamp, fit insulated terminals to your leads onto the battery, and forget about it. If really worried, get a fully sealed AGM (absorbed glass mat) battery or similar, one of the ones you can mount upside down, as well as doing previous things (I did this because mine was sloshing acid out the vents everywhere).
As far as air getting in your fuel line - it won't shut your EFI down. What will happen is your fuel pump will suck air, thus the fuel supply will drop until the pump picks up fuel again. This then means your injectors aren't injecting as much as they are supposed to (the ecu is calibrated to open injectors for X milliseconds at conditions Y (rpm etc), which at a given pressure will let a certain amount of fuel through. Lower pressure means less fuel comes through). So if you were to have the pickup feeding air for one second, then you would get about 1 seconds worth of lower fuel supply (a lean condition). This can cause detonation, which can be a problem under load. Of more concern however is that the fuel pump may die when asked to pump air (possibly due to overspeeding?). Also of concern, is now that the pump is filled with fuel vapour rather than liquid (the liquid part of petrol is not flammable, and actually cools the pump down), sparking from the armatures inside it may conceivably cause an explosion, turning your fuel pump into a grenade. Very rare, but it can happen. Only with roller cell type pumps, I'm fairly sure, and even then I believe they may have designed a safety feature into the newer ones anyway. The facet style pumps generally used as a lift pump don't have this issue to the best of my knowledge, and will simply die if pumping air for long periods of time.
VL commodores do have a lift pump, GTV6s don't as far as I know, the pump simply takes fuel from the lowest point on the tank, via a large banjo fitting.
