Differential Girdle Too close to Gas Tank?

[JR_Charger]

I figure I'll have to lose the external brace kit, the shocks get in the way as well, but the girdle may also be too deep. Then again, I could be misunderstanding how the axle moves when the suspension compresses. I was thinking it must push back, but the bump stops are forward. So it must be rotating forward, maybe the girdle is o.k.?

 

[dvw]

Depending on suspension, the rear housing usually moves rearward as the car is lowered to ride height. My race car runs that same cover. No girdle. Car runs 1.2x 60ft. it's been run over 1000 passes over 11years. The housing is still straight.
Doug

 

[j-c-c-62]

The problem as I see it, it likely in "normal" use would never puncture the single wall metal stock tank. However, in any real shunt it will, and with metal-to-metal contact likely initiate a fire on contact, and things will go downhill very quickly.
I would consider installing a metal container/bladder fuel cell slightly located farther from the rear.
Think Pinto:

"Design Flaw[edit | edit source]​

The Pinto controversy centered on a single design flaw which made this “carefree car” a potential deathtrap. Ford engineers chose to place the fuel tank at the back of the car, directly between the rear bumper and rear axle. This fuel tank placement was common for domestic and foreign cars at the time, and was considered a conservative choice compared to the untested above-axle design. However, the potential dangers of this placement were exacerbated by other decisions made in the design process. Due to Iacocca's cost constraints, the walls of the fuel tank were exceptionally thin. The fuel tank design also incorporated four poorly arranged bolts, which protruded from the rear differential directly adjacent to the tank. [2] Rear-end collision tests showed that, in collisions over 25 mph, the protruding bolts punctured the thin walls of the fuel tank, resulting in fuel leakage. Sparks into this leakage had a high chance of ignition, culminating in fatal consequences." Professionalism/The Ford Pinto Gas Tank Controversy - Wikibooks, open books for an open world

 

[6PKRTSE]

It looks like you will be fine with clearance without the back braces. I run the same girdle cover. I don't think you need those back braces either.

 

[JR_Charger]

If the axle moves backwards, why aren't the bump stops a few inches back from where they are?

I think I'll put the factory cover back on. Realistically, it's going to be a long time before I get out of the base 318 business. This little experiment has been educational though, so it's not a total waste. I'll have to look into the fuel cell idea at some point. I don't need an excursion from the road to end in being burned alive. I've been knocked off the road before, no reason why it can't happen again.

 

[j-c-c-62]

Understand, in any kind of incident, it's more likely the fuel tank will move more than the rear axle, regardless, the result is the same.

 

[JR_Charger]

That's true too, the way it's fastened the tank can absolutely slide forward. The straps will swing and they'll also bend out of shape. Better to have it impact the round factory cover than even the LPW cover, which will still have those set screws sticking out.

 

[rickseeman]

When Big Daddy ran a Dana 60 in Top Fuel he didn't have that girdle on there. (Which I don't know if that does anything anyway.) He also didn't have those bolts to tighten up against the caps. Take off the girdle, take out the bolts that stick out and put in short bolts to plug the holes. I like cast covers. Let's be honest, I think you're making less horsepower than Bigs.

 

[JR_Charger]

I'm not currently making any horsepower, just planning ahead.

The Dana 60 is much stronger than the 8 1/4 - and heavier, and less efficient. I'm on the "simplicate and add lightness" program.