funina91ss

The meserments were right on.. I used a 3/8 drill bit and drilled a whole and used tin snips no sparks at all .. I am like you waiting a the fuel pump so I havent taken it out yet still have a full bottle of N20 to run out That is if the guy who owns the car dont care.. I am putting in a grantell 255lph pump for a 150 shot on a stock motor

dave1w41

Best looking hack job I have ever seen. Looks good but unless you are going to do it right don't bother. If I were buying a used car I would not even consider one with this "modification".

If you need to know why this is a bad idea, maybe you should just e-mail me. I don't need to go into the discussion yet again. All I can say is that from the opinion of a Service Engineer do not do this. Do it the right way or hire someone to do it the right way. The best mods are ones that don't result in .

MACGI 98 Z28

The only proper way to change out the fuel pump is to drop the tank in accordance (or close to it) with GM service procedures found in the helms manual. Chopping a hole in the floorpan is HACKING and it is a bad idea.

RamAir95TA

Why does it appear to be 'hacking'? I think the cuts looks professional.

And why is it a bad idea?

Taking the proper precautions, taking your time, and doing it right, and it's plenty better than dropping the tank, personally.

funina91ss

Then maybey everyone should keep there cars stock I dont see gm serivce man. foor roll cages,subframe ties,SUMP TANK,and the list will go on if you are worried about strucal integ if you screw a plate back on it will not hurt any at all that stuff is already thin and it is not really a high stress point of the car Just be smart like you would doing any other mod to your car and to the post about used car If I was selling a car I would just not tell

shoebox

More than likely, because it compromises the unibody integrity. One purpose of it being to protect the occupants from the contents of the gas tank in the event of a crash induced rupture. I am surprised this has not been brought up sooner in the thread. I guess because it has been already in so many others.
In a crash, there could be great stress put on the fasteners that are used to hold the panel on. I would imagine if the occupants happened to die in a fiery crash and insurance investigation found the access hole, they would not be likely to pay out any death benefit. Just a thought.

grendal

On MOST cars, the fuel pump/sender unit is bolted in directly into the passenger compartment, usually in the forward area of the trunk and/or hatch.... Doing this mod actually just makes the 4th gen more modern..... As in one example, using a panel, sealant and screws actually puts you a step ahead of most cars in safety.

I'd do it... and probably will....

If your reason for saying this is so bad is so right, how about you just go ahead and tell us....

-Michael

shoebox

You lost me, dude. What "most" cars are you talking about? I have never seen any car that had the fuel pump in the passenger compartment. (guess that doesn't mean there aren't some) Plus the gauge sending unit/float arm would have to be installed in the tank.

If a car is designed with an access panel that is one thing. When one is added, well, that is another. Cutting a hole does compromise the original intended design. Whether it is safe or not, I am sure will be determined sometime in the future.

Now, what is it you want me to "tell you"?

Dan95TA

I think the big apeal to this install is that it sounds very easy. And dropping the rear end sounds hard. When my pump was going out I thought about doing it this way too. I decided to do it the right way because I did not like the idea of cutting a hole in my car and risk hitting the fuel lines. After doing it the right way I would never even consider doing it this way because I learned dropping the tank is so easy.

Dropping the tank cons
taking off the exhaust could possibly be a pain, and dropping the tank is a little tricky but if you're small like me you can just angle it to get to the pump assembly without even taking the tank completely out. Oh and a bunch of bolts.

Trap door cons
Risk of hitting a fuel line while cutting and possibly causing injury, compromising the structual integrety of the the car, possibly inviting rust, and possibly spilling gas from the assembly inside the car. Also like shoebox said that I hadn't even thought of, about getting in an accident.

The only good thing about the trap door is that it might make it easier to get to the pump if you somehow mess up the install. So if you drop the tank just don't mess up


how is this safer than having a SOLID sheet of un cut metal

I would be mad as hell if I bought a car with this mod done to it and wasn't told especially if it was rusting.

Now I am not trying to tell anyone how to work on their car, do whatever you want, I am just posting my experiences.

grendal

No, what I mean is in MOST CARS if you pull up the carpet, there's ALREADY AN ACCESS HOLE TO THE TANK/SENDING UNIT. In fact, THIS IS THE NORMAL WAY TO CHANGE IT.

Some examples that I've seen with my own eyes? 1998 VW Passat, 1988 VW Golf, 1990 Toyota Corolla, 1989 Toyota Camry, etc.... When you pull back the carpet, you unscrew the round access panel and pull back the sealant, when you lift up, you pull out the entire sending unit/pump assembly... right in the cabin of the car.... then you replace it the same way, re-seal it and screw it back in.... this is NORMAL PROCEDURE for most other cars. It is BAD DESIGN that you have to drop the tank to do it on the f-body...

NOW WHY DON'T YOU TELL ME WHY YOU THINK IT IS SO DANGEROUS AND/OR BAD TO DO IT BY CUTTING AN ACCESS HOLE? Mr. smarty pants

YOU are the one who says you have some really detailed reason that you don't want to go into... well, go into it... tell us why.

Fire Risk? How so... compared to most other cars, you still have double protection.... the sealed tank itself AND a sealed metal panel... vs. most cars just having the sealed tank entry point in their trunk/hatch. Besides, if your tank ruptures in an accident , you have much bigger problems.

"Hack Job" on the body? Pure opinion, and not a really educated one. As you can see from the pics and the discussion, they are not cutting through the structural part of the body. In fact, if you look at the reinforcement "ribs" that are molded into the body panel there, you'll notice that CONVENIENTLY GM actually stopped the reinforcement rib in just a perfect position so that a hole could be cut there.... coincidence? Or maybe completely on purpose... Why wouldn't that center "rib" go all the way up? Why does it conveniently stop right where you need to begin cutting? Furthermore, if this metal in this area is so thin that you can cut it with TIN SNIPS, it is ignorant to believe that it would be any weaker with a thick metal panel screwed in its place.... If anything, with a thick panel screwed down with 10+ screws, this area is at least "as-strong" as before, if not stronger. And if sealant is used, as suggested, it also eliminates any concern of fumes.

So, please. Please tell us your reasoning for this being such a bad idea.

-Michael

shoebox

I already said that cars designed with access are one thing. The key element in my mind is designed with it. If you have to cut a hole, it is not part of the design, even if it appears a convenient spot was left to do so. The way I understand a unibody car is that the whole structure is designed to work together. Removing what appears to be an inconsequential piece of metal may have unwanted consequences in certain circumstances. Panels can be made thin because of the way they are designed to work with the whole. I am no structional engineer, therefore I choose to err on the side of caution.

As I see it, if the metal around that area is deformed in a crash, that panel is apt to come off. If it was secured with a good grade bolt and nut, that could make a difference (of course, getting a nut under there would require removal of the tank ). A sheet metal screw is not much to hold it in that situation.

Sure, you will have big problems if your tank ruptures, but even bigger problems if that gas is inside the car with you.

Like I said, no engineer, just MHO. If anyone thinks this is a concern then don't cut. If you think it is safe, go ahead.

funina91ss

Here is the way I see it if you hurt your car that bad to smash the floor in it you are pretty much a goner anyway and stiffing of the f-bodys is a popaular mod and also affect strucal integ. gm did not crash test F bodys with subframe conn. and roll cages so what is the diffrence in cuting little hole just use a drill bit with a stop on it so it wont go down to far and tin snips and you have no sparks to set a flame and if you ever have a porblem with the pump or want to upgrade it will only take 30 min to change No dirty hands either but to each his own I guss!!!!

MACGI 98 Z28

IF the tank ruptures, do you think a couple of screws and some sealer is going to keep you from becoming a human torch? I would rather have the floor there even if it buys me only a fraction of a second. That tank is really not that far away and if the hit blows out the "panel" the contents of the tank will be INSIDE THE VEHICLE.

Who has the "opinion" here? Are you an engineer? How do YOU know what is and is not structurally critical? What are your qualifications in this regard? If GM "conveniently" made it for cutting, why does the service manual not have the hack procedure instead of the one that shows you how to drop the tank? Do you think maybe they have a good reason? I am betting on "coincidence" here.

iniviate

the rib is removed to make room for the fuel lines that come out of the tank.

i dont think there is really a valid argument to cut the tank on most cars.... other than it saves time, especially if it fails again.

with that being said, i cut mine.

dave1w41

Just because VW and Toyota did it does not make it good practice. GM has an access panel on a few cars but they are designed into the structure. The floor panel is thicker, the cover is held on with weld studs coming up and nuts that thread down over them (not just some sheet metal screws). The panel openings in all of your examples have rounded corners and rolled edges that add structural integrity.

A square hole is the worst one to have in a structural panel because it deforms at the corners. It may not even take an accident to deform this type of opening (square or rectangle with 90-degree corners) in a thin piece of sheetmetal. Over time cracks may begin to form at the corners of the opening because someone made 4 perfect stress risers in an otherwise undamaged floor panel.

Take a look at all of the other openings in the floor panel. The shifter hole, the body drain holes in the footwells and trunk well, how many of them are square with square corners? They aren't because openings like that are bad news in a sheetmetal panel unless the panel is over-designed to make that opening possible.

It may deform enough in normal driving to allow carbon monoxide to enter the car. It is risky all around and the reason that there isn't an access panel is because it was determined that there should not be one. Saying that piece of metal isn't structural is just an opinion from an uninformed source. An informed source (like myself - an automotive engineer) will tell you that there ins't a single square inch of metal that you can identify in a car as "not structural" without having actually engineered it yourself. Very, very, rarely is any part of the floorpan of a car not imperative to the performance of the car in crash and high-load situations. Get under the car and take a look at what is attached to the rails near that new opening. The rear axle and the panhard bar attachements. What kind of loads do you think are spread through that useless floor when you are cornering at 1.0G's and the panhard bar is absorbing 80% of that load? Not structural?
Take a good look, those formed areas of the floorpan, they aren't there by accident. Those are like the corrigations on a tin trash can or a metal silo on a farm. They add structure to the thin sheetmetal and lo and behold, someone has just ground a hole through that structure in this picture. If you look more closely you can see rows of spot welds attaching some structural braces from underneath. What are those for? What kind of loads might be passed through those structural braces that are now located near this hole? Bueller? Bueller? Maybe you don't know because, well, you don't know and, well, maybe cutting is a bad idea?
If you didn't know better the siren song of "easy fuel pump replacement" might be sounding pretty good right about now.

Removing the rear axle sounds like a huge job but really isn't. Cutting holes in the floor IMHO is just chicken****ting out of taking on the real job. If you can't handle the work, don't modify the car. BTW, this does not qualify as a "mod" that would show up in a signature. Modifications are by definition to improve the performance of the vehicle. Cutting a hole in the floor of a car does not qualify as a "mod" because it will only degrade the performance of the vehicle in one way or another.