Will I need a larger battery for my starter and CR?
 

I have a modified 1980 engine which has 3.2L and a 10.3:1 compression ratio. I also have a high torque starter.

I would like to go to a Group 48 sized AGM battery to replace the current 49 lead acid one in order to save about 10-15 pounds.

The car is used nowadays only in warmer temps, say above about 2C or so.

What do you think. Can I go with the Group 48 AGM? Thanks.

Paul,
You should be fine . . . we use a garden tractor battery in our race car with 12.5CR 3.8L race engine . . .cranks great !!

Regards,

The geared high torque (and lighter) starters really do the trick. What you don't get with smaller batteries is duration - if you are having troubles starting, you can't keep cranking for as long or often.

This^, if you want to insure great cranking replace your positive cable with a larger gauge cable, less amperage lost to heat. Add an extra ground strap, do everything you can to eliminate resistance.