NEEDS FOR 2 BATTERY SET UP

I'm moving from the simple Moroso water pump to Meziere 42 gallon pump and a larger electric fan. Looking to use 2 battery set up. Do I need to increase my alternator to 100 amps? Presently 1 wire 60 amp denso style. Strictly a track car.

No. Should be fine. I run same setup with 57 Amp Jones alternator.

I ran 2 12 volts for 7 years. Starting was not always optimal. Got to the point I had a small jump box between the seats. Had to use it more than once. 75 amp alternator. Last year went to 16 volt. Best thing I ever did. One 16 volt starts it way better than 2 12 volt ever did.
Doug

If you are going to use two 12V batteries I’d use a series-parallel switch and fire the car off of 24V and never look back. The engine will start quicker, the batteries will hold a charge longer and it’s just a better way to do it.

I learned that with a two group 24 RV marine deep cell batteries and a good alternator it helps to slow charge the batteries before race day, that way they won't have to rely on the alternator to keep them near full charge after sitting between races.
I use a 4 to 6 amp charger and let it run 24 to 48 hours before taking the charger off, I also use it during our lunch breaks at the track to top them off

W/r/t I’d use a series-parallel switch and fire the car off of 24V
Mercedes did this with great results

I have never run 2 batteries ever if you are running a alt... I had the same battery in it for
7 years.. the battery was still good but I changed it out

I learned how important proper wiring and good connections are. Had my car professionally rewired year before last.
Going rounds, running electric water pump and fan, etc, etc. one interstate battery and 90 amp 1 wire alternator... not had a battery charger within 50 yards of the car one time since..ever. Car starts like its got 16v system on it every time.

Same here Mr P.

I ran a 16 volt battery many many years ago before it was the cool thing to do. They were made in New Castle Pa and rarer to find then Hens teeth. I was always afraid of it going bad at one of the long race weekends I raced at so I took a good Sears Platinum 12 volt battery with me to a test n tune one night. I ran 8.66 with the 16 volt and 8.66 with the 12 volt battery. And this was before I was smart enough to run an alternator. I ran the 16 volt for another year till it was getting older and never ran one since. There’s one sitting in the heads up car I bought five years ago that will be getting pulled out to. We were all in a hurry to pull our alternators out of our cars 35 plus years ago and it was the stupidest thing we could have ever done. Lol 😂

I'm always running the fan and water pump after I make a pass. Wound up going rounds at a 250+ race. It seemed lazy for the last start up. Only have 2 smaller LED lites for heads lites. It was too late to diagnose and I blew it in the 1/4 round. Never made a covid race last year and the battery needs to be replaced this season. If I'm replacing, then adding to or taking off, its time now to do make some changes.

I manage a battery distributorship and we are two miles from the dragstrip. Its rare but we get the occasional panicked call of someone looking for a 16 volt battery. The only way we have to make 16V is two 8V golf cart batteries, no one has been that desperate yet.

I suppose its probably not a big deal to convert to 12 volt for a weekend if you are carb'd? An EFI car might have an issue if they didn't have good injector data entered.

Back in the old days it was a common practice for people to remove starters also to reduce weight. This was primarily in altered and dragsters and classes like that. Everyone push started their cars. I went to the AHRA Nationals in 1961 and I was the only mechanically fuel injected car that started my car with a starter, I was able to do it and it was much more convenient.

I run two twelve volt batteries. One for the ignition one for everything else being Meziere pump, electric fans and fuel pumps.

I don't run an alternator.

I do charge the batteries between rounds.