This wasn't difficult, especially since my passenger seat and HVAC were already out of the way, but the end is well worth the effort.
The group 49 battery weighs a healthy 58lbs. It may not look like much, but put that weight on the end of a lever and you get the idea of how much influence it really has. This moves the weight from above and forward of the car's center of gravity to behind and below. This gives less body roll and brings the car closer to 50/50 weight distribution (Very difficult with a heavy diesel up front!).
The main reason for doing this, and what several other of my plans require, is the freeing of a significant volume of engine bay real estate.

I used 13.5' of 1/0gauge battery cable from battery to starter. This was BARELY long enough, I had 4" left over. Anyone considering this mod should get a minimum of 16'. I also doubled up the 8gauge harness wires from the starter to the fender mounted distribution block so I won't have to mess with it later when the alternator is upgraded. I replaced the solenoid wire due to exposed wires in the old one.

Here you get a feel for just how much area the battery and tray really occupy. 4 bolts hold the tray in place. I drilled out the 5 spot welds on the tray to remove the arm, cleaned and painted it. Luckily, despite the tray being rusted away from acid in one corner, the body is undamaged. Nothing some good soap and a power wash can't handle.

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The cable passes through the old evaporator hose grommet and into the existing harness covers. I threaded one of the old insulation pad studs to accept a 10-32 nut to secure it to the firewall.

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I planned to run it with the vacuum hoses over the wheel hump but 13.5' was 2' too short. I drilled a 3/4" hole in the rear bulkhead and passed the cable under the fuel tank. I collected over a dollar in small change and 10lbs of white dog hair under the back seat. Side note: I wish I had thought of this harness route when I installed the air system in the 240, it would have been 10x easier than running it under the body.

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The fuel tank has plenty of clearance underneath and only a small corner was cut off the cover panel. The modified stock tray is bolted to the floor and a body ground strap is used. Gasses are routed outside the body. I put a nut on the tire hold down rod and use it to prevent the cover board from touching the battery. The loss of the spare tire is no problem for me, I've never needed to use the spare in any of my cars and I have AAA.
Rust was a big problem in the trunk, notice the hole in the upper left. I used my air sander to clean off every rusty surface, put two cans of undercoating over everything and replaced the missing rubber plugs that were letting water in.

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With the carpet in place, nobody will notice its there!

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I might consider doing the same to the 240 much later on if I get bored, but for now I have no need for the extra engine bay room.

Looks clean. Is the ground cable terminate to the spare tire well?

Engine bay room? VGT and intercooler space?

Yep. Cleaned down to bare metal for good conductivity then covered it with rubberized undercoating. The battery had to go because I need the area for both the 4" intake tube to pass through and a place for the intercooler's water reservoir.

Why not behind the wheel well?

Not wide enough for the tray.

I just noticed the tray is still in there. What I'm planning on is putting my battery behind the wheel well, having a fuel cell in the spare well, and the tire on top of that, if there at all.

I looked everywhere but nobody sells a marine battery box big enough for a group 49.

(04-23-2009 01:26 AM)ForcedInduction Wrote:  I looked everywhere but nobody sells a marine battery box big enough for a group 49.

Really? About5-6 years ago I loved the battery to the trunk in my Merkur. I had a space W123 battery and decided to use that instead of the silly little stock one. My local auto parts store had a marine battery box that way the perfect size. I'll check to see if it still has the p# on it.

Added the ground strap from the last manifold bolt to the old monovalve mounting bolt.

(04-22-2009 05:26 PM)winmutt Wrote:  Why not behind the wheel well?

Because It will get smashed if you are rear ended!!!! Ask me how I know....

Plus the wheel well would be a little too far behind the axle. Like the lever reference in the first post, the further out from the axles the weight is the more its momentum/inertia will have a negative effect on handling and suspension movement. Ideally I'd like to have it right in the middle of the car, but I really don't want a gallon of sulfuric acid in the cabin with me.

Definitely lets set the motor back in the firewall a bit too!

The 617 would only work about 3/4", not really worth it. The 616 could take 2-3" though but you'd have to take a chunk out of the oil pan. If I were going to that much trouble I'd swap in a more modern compact engine like a TDI or 4HE1.

Dude you way over thought that one. lol i was joking. hehe I know in, for example, drifting a V8 car they move the motor so that it is completely being the front axle for the leverage point you were speaking of.

Goodies! Well minus the coffee cup...


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Hello everyone,We wanted to relocate the battery to the trunk in our late '60s GM A-body for a number of reasons. First, it's a modification in keeping with the musclecar era just like headers and traction bars. Placing the battery as low and as far rearward as possible would greatly improve off-the-line traction and overall handling. More significantly for this daily driver is that we are installing a new Sears DieHard Security battery as an anti-theft device, and keeping it locked in the trunk adds another level of security. Finally, from an aesthetic point of view, engine compartments look much better without that black lump up front in full view. And for those restorers who are purists, this restomod is easy to undo. Just six holes in the trunk floor and a few small holes in the frame to fill.

(08-05-2010 06:37 AM)Ugsjhuy Wrote:  we are installing a new Sears DieHard Security battery as an anti-theft device

Anti-theft because nobody would even bother to steal that junk!

Beat it spammer.

(08-05-2010 06:41 AM)ForcedInduction Wrote:  

(08-05-2010 06:37 AM)Ugsjhuy Wrote:  we are installing a new Sears DieHard Security battery as an anti-theft device

Anti-theft because nobody would even bother to steal that junk!

Beat it spammer.

Why don't you just delete that post?

(08-05-2010 10:29 AM)Captain America Wrote:  Why don't you just delete that post?

Talk to winmutt.