How Big A Battery Do I Need ?

Thanks Tim, the good thing about Optima batteries is that they are fairly light compared to the "ingot of lead" I was using.

Terry: I’m using the Optima 800. More than enough power. With your rebuilt engine, it may be a little “tight” until the engine has a few hours on it.
Tim.

Hi Mike.
I have good cables with good grounding points and a rebuilt starter motor.
Looking for information on the Internet I found,
The rule of thumb is 1 CCA per cubic inch engine capacity for petrol engines.
The Cord is 289 cubic inches and has a lower compression ration than modern engines, consequently the 600 CCA should be more than adequate considering the mild climate here.

I have a 950CCA in my Marmon 16, 490 cu. in. Don't think you would need anything that big for a Cord. That presumes you have good grounds, big cables, good starter, etc,etc,etc.
CORDiallyMike

I'm on the verge of buying a new 6volt battery for my 810 Cord.
In the past I had used a heavy duty battery that gave 900 CCA
I believe 6 volt Optima batteries give 800 CCA
I have another option with a conventional 6 Volt battery that gives over 600 CCA
My question is how much CCA do I really need?