I'm having a Corvair built with a 5.3L LS4. Amperages are estimates-Dual electric cooling fans(15A), electric water pump(8A), manual windows, standard stereo(10A), Holley Dominator EFI(10A), Heater blower (10A), stock lighting(10A), No AC/PS, N/A, Rear engine/front battery, manual trans. Do not plan on driving in below freezing temps.

Space is limited, trying to keep weight down. During startup really only the EFI and battery is going to be on, but I guess if it's hot the water pump and fans could come on. Any idea how many amps to crank a stock motor?

Odyssey makes a nice small 680CA. Comments, questions, concerns?
thanks in advance.

 

I think you will be fine with that cca. I am that's around what my car uses and it starts great.

 

I used the largest lawn and garden battery the store had and it works fine. It is a U1LUH and weighs 19 lbs. It will start the car 10 times in a row (with no re-charge) before it starts to struggle. In normal driving where the battery has a chance to re-charge it works perfect. All the accessories will be run off the alternator so battery size really does not matter for those unless you are planning a stereo competition. Mine starts fine with the spal fan and walbro 255 running.