Lets see if anyone knows this answer. I'm trying to finalize these gas tanks for your guys but I have a question in regards of the stock gas tanks.

If you look at the bottom half of the tank (its the same from 79-85 only the top part has changed btw) you will notice that there is a rounded section that looks like it was made to clear the differential casing. But the the tank sits about a foot away from it and the heat shield in between the tank and diff is a straight edge piece.

The only thing I'm not sure of, is did the 79-80 gas tanks sit further inward of the chassis?

If it doesn't then I think when mazda was designing the parts, they originally planned to move the tank as far inward as possible, but a relocation further out to possibly better balance the car was put into effect? And since they already had a mold of it why add more cost to do another change? Am I right in my thinking?

The reason I ask is because I would like to increase a bit more capacity and if I don't have to put that hump in there, it would increase it by quite a bit and also simplify the design quite a bit too.

Sam

 

I just peeked under my SA just now and it has the same scallop out of the front of
the tank and the straight shield between the diff and tank. Theres a lot of space
between the shield and the diff just as you described.

Heres my theory on why the tank is shaped that way. It's to make the tank ride up
over the diff in the case of a big rearend collision and possible preserve the tank
integrity. Trying to avoid the exploding pinto phenom as it were.

How much extra capacity would it give us anyway?

 

I always wondered about that indent. TG has a good idea about it.

 

i was just looking at that on mine, although i didn't SEE it.... i bet it is there for crash protection.

 

yes my 79 has the same indent and spacing. With that said do we have a date or deadline set? If so and it is sooner than I need I will jump. As you know my car is in the middle of it's swap and I will need to solve the fuel problem in two weeks. if you say september-october I will toss a presure fitting on there and wait if later than ocotber I will have it welded

 

The overall shape is pretty much done right now, I'm just working out electrical issues currently. I'm trying to find a supplier for replacement fuel level sending units that work at the exact same range as stock so you would just need to wire them in. I'm most likely going to have one laser cut and ready to be welded next week sometime.

 

Are you saying you don't see an indentation on your car?

 

I haven't fully calculated capacity yet, but I believe about 3L or so.

Good thought on the crash protection idea, but I would believe that if anything happens from the rear end collision, there would be more metal coming in from the back of the car into the tank and puncturing it as such. Alot of the old school domestic cars have tanks in the same position and are actually closer to the differential with no such clearance as such ... not sure its the best thing to compare to if you guys know what I mean

 

Sam,

How`re you making out with the tanks? It's on my list of things I need since my last safety. And I just realized that I've been typing with my keyboard set to 'Canadian French' all day.

 

Would someone with a SA be willing to remove their springs and shocks (with the rear-end supported with jack stands) and jack up the pumpkin to see if there is an issue with interference between the pumpkin and the tank?

 

 

He's wondering if clearance is needed for suspension movement (my guess)...

 

no issues. doesnt even come close to touching.