Battery set up / dimension question

[dave 911]

I've searched all the 'battery' posts I could find and I'm still not clear on what battery size I need for my 76 911. I have 2 threaded holes in the bottom of the battery compartment, the inner one (which I was not using looks like it's for a battery that's 7" long. None of the local Auto Parts stores have batteries that will work - they either don't have the tabs on the bottom, or the posts are flipped.

So here are my questions:

My current battery is 10" long (not counting the 'tabs' on the bottom) and 6.25" wide. It's an Exide 840 (dated 6/2000, it has a bad cell and is dead) Is it a group 48?

This one looks like it will work - the posts are on the correct ends, but I can't find dimensions of it anywhere on the website....Advanced Gold AGM Battery - Group Size 48 (Price with Exchange)- DieHard-Automotive-Batteries-Car Batteries. Can anyone verify the dimensions of this battery?

Is my set up standard? Can someone w/ a 76 verify their battery dimensions and post locations for me?

Thx

[dave 911]

Here are some photos of my current set up. Are these post locations standard?

The cables look long enough to reach the other side of the battery, but would there be a concern w/ the posts being too close to the body of the car?





And on second look the Diehard I linked to in the above post has posts opposite of mine....

[Joe Bob]

That's how mine is set up. Group 48 is what I think you need.

When I did my Optima, I needed to extend the braided ground strap. I also use marine style terminals with the wing nut disconnects. Saves wear and tear on the leaded pinch clamps when I want to kill the battery for electrical work.

I see you have a battery disconnect on yours.

[dave 911]

Thanks Joe Bob - which Optima did you go with, and did it have the tabs on the bottom ends so it was a straight swap out, or did you have to fab up a new hold down system?

I saw nineball's setup in another thread, and it looks great but i'd prefer to get something that's more plug and play, if possible.

[Joe Bob]

Mine is so old it has grey nut sack hair.....

It's an Optima Yellow Top. 8+ years and still going. I have an over the top clamp.

I'm sure they have changed everything on them by now. I DO know the marine yellow tops have dropped from 3 t0 2 years on the warranty and the price has tripled since I bought one.

[aoncurly]

There are two different Interstate batteries that will also work. There is the huge battery like you currently have, or you can use a smaller one too.

[KTL]

Smaller battery is group 91. I have an Interstate MTP-91 that has served me well for almost ten years. Not saying Interstate is great. Just saying mine fits and has lasted me a long time on a sunday driver.

edit....... My Interstate does indeedy have the correct tabs/feet on the bottom to cinch it down properly in the original battery location with the factory small metal holding tab

[dave 911]

Thanks Kevin -

Which side are your battery posts on? I see a a MTP-91 on their website, but the posts are flipped from mine, and that would put the posts toward the fender vs. inboard by the gas tank.

I don't see a MTP-91R on the site...

Thx

[aoncurly]

I have the large Interstate battery, and the posts are both toward the fender, but they fit fine. I don't have the extended connector on the ground post though. The "standard" negative connector looks similar to your positive connector. Someone added that extended connector with the green knob.

My 81 SC has two holes on the bottom that will accept the larger battery or a smaller one. There is a clip with a bolt that screws into the holes to clamp the battery down. The Interstate battery has a lip on the bottom of the battery to accept the clip.

I just replaced my battery a few months ago, but if I could do it again, I'd go with the smaller MTP91 Interstate battery. It's cheaper by about $70 as I recall.

[nineball]

another battery install thread

[JAR0023]

Originally Posted by aoncurly

I have the large Interstate battery, and the posts are both toward the fender, but they fit fine. I don't have the extended connector on the ground post though. The "standard" negative connector looks similar to your positive connector. Someone added that extended connector with the green knob.

My 81 SC has two holes on the bottom that will accept the larger battery or a smaller one. There is a clip with a bolt that screws into the holes to clamp the battery down. The Interstate battery has a lip on the bottom of the battery to accept the clip.

I just replaced my battery a few months ago, but if I could do it again, I'd go with the smaller MTP91 Interstate battery. It's cheaper by about $70 as I recall.

My battery also has the posts on the outboard side. Duralast 49L. The battery does have a guard that folds over the positive post for protection. Came with the car. I won't buy a replacement that large. Looks big enough to turn over a Peterbuilt.

[KTL]

Sorry I forgot to respond to this. Yep my Interstate MTP-91 has the posts on the outboard side close to the chassis wall. It's a bit of a tight fit but not problematic.

Actually it's good practice to put some kind of cover over your battery terminals & cables where there's bare metal exposed. Most racing/track organizations require you to have tape over both the neg. and pos. terminals for tech inspection approval.