FRMULA88

The OEM battery is Group 75 those dimensions in inches are:

L 9.38
W 6.81
H 7.75

I have 720 CCA 910 CA group 75 starting battery but have a hot start issue.

I replaced my battery cables from the OEM #4 to #1 gage

the starter is MSD 3HP mini-starter which is plenty. ( draws 75 to 100 amps when starting )

Even with the larger cables I still think this battery is not going to be enough when this engine is hot. (13:1 compression) plus I want to run my cooling fans in the pits.
and not have to lug a generator and battery charger to the track all the time. (car has an alternator)

So I want to use a Group 31 deep cycle / starting battery in the stock location 900 CCA 1125 CA
but obviously it is larger.

L 12.81
W 6.56
H 9.38

roughly 3.5 longer & 1 5/8 taller

I am not worried about the W or H.
I think I can solve the Length issue by making block to get rid of the sump the battery tray sits in.

Anyone try this ?

I am looking at the Optima blue top since it has 5/16-18 threaded studs I don't have to redo my side post terminals and also can connect the alternator charging wire and ground for my MSD box.

Bob88GTA

iTrader: (2)

13:1 compression

Wow, Lotsa cranking power!

357 Camaro

I did it i think mine is 10 or 11 inches long. What ever it may be it would not fit. I thaught of the option to move it to the trunk beside the fuel cell ( which i will be doing one day). I got a piece of aluminum cant recall the gauge. I covered the sump made it look neat. I mounted my hold down kit for the battery it doesn't move or ne thing but It is rather close to the fiberglass hood tho.








Should mention i have a xs power battery. Like 6 maybe 7 inches tall 7 inches wide

AlkyIROC

Mine isn't in the stock location but I ran a group 31 battery for a few years in my race car. 950 CCA 180 minute reserve. Although it worked fine, it was just too heavy. Group 31 batteries are around 60 pounds.

I went to Walmart and looked for something smaller. Can't remember the group number but it's like a 25-30 pound battery and smaller than the group 75 battery. Something like 450 CCA and has no problems cranking over my 14:1 compression engine (I run alcohol fuel). Of course I also don't need to start my engine when the weather is anywhere near or below freezing.

Running an alternator, you also only need 1 battery. I run a CS style alternator so it puts out a lot of amps at lower rpms.

FRMULA88

I am not concerned about the bit of extra weight, so long as the engine start when it is heat soaked. A lighter car that can't start in the staging lanes is not an option.

The observation I made is if I want a combination deep cycle / starting battery and not lose starting amps I have to go to a larger group size.

For example the Optima Yellow top group 75 battery is 620 CCA 770 CA.
substantially less than the red top model. Red tops are starting batteries only.

Doing a bit more research
A good compromise could be the 34M series. The Optima yellow top has side post & SAE post.
The blue top has SAE & 5/16-18 studs both are 750 CCA 870 CA.
The width is only .07 larger, Height .19 larger, and Length .68 larger.
The weight is only 10# more than the group 75 model and does offer a bit more amperage than the red top ( CCA amps )

Using a deep cycle / starting battery means I can run my fans in the pits for 3-5 minutes ( water pump too if I switch to an electric pump) and still have reserve to start the car.

but being racers more is more..

The group 27 steps it up to 800 CCA 1000 CA
compared to group 75
same width
only 1 inch taller
the Length iss 12.19 so 2.81 larger.
this may be the one to work with versus the even larger group 31.

AlkyIROC

If you need to run your fans and water pump for that long in the pits to bring the temperature down, don't rely on the battery alone to do the job. The engine won't run long enough during rounds to bring the charge back up.

FRMULA88

needing and wanting are completely different.

I need to solve my hot start issue. but I also want to have the flexability to cool the engine between rounds.

A fellow racer uses a deep cycle / starting group 31 battery.
He cools down for a few minutes in the pits. with the engine off it does not take long to bring down the temp by circulating the coolant and running the fan(s) for a brief period.. the car Never needs charging and two less things to lug to the track (generator and battery charger)

I am always impressed by the innovation I see in the pits and I try sort out the stuff the really works versus the stuff which creates more work and apply it to my program.

Not wasting money on a generator by having a high output starting system seems like a really good idea to me.

I think their is a benefit to using a high capacity deep cycle battery but that is my opinion based on observation.

FRMULA88

Thanks, but what I really need is some relevant input to my question.

If no one has shoe-horned a bigger battery in a 3rd gen's stock location that's fine. I thought I would put it out there to see what has been done.

The obvious choice is moving it to the rear where there is all sorts of space but that creates another set of issues ( mandatory kill switch, & long runs of 1ga wire or 0/1 wire.)

under the hood keeps the wire runs short and a kill switch is not mandatory.

with an already lightened front end and a propensity for nice comfortable non oil pan damaging wheel stands. I like the notion of keeping some extra weight up front ( ballast )

o yes and I tried that was the first thing I did..

Maybe I am overthinking this.. bad habit of mine sometimes. I will try and see if the new heavier gage cables and current red top optima will get the job done.

I also beefed up the grounding; #4 ground strap on the passenger side cylinder head to the chassis and a 1/0 ground strap on the driver's side engine block to the chassis. (More room on the driver side to get to the block) The 1 ga negative battery cable is also grounded to the chassis.

My heads are attached to the block with laminated steel/copper head gaskets (cometic) so the 2 large grounds straps on the block and head should provide the starter and alternator with plenty of easy paths to ground. My old setup had just the #4 negative battery cable attached to the passenger side motor mount on the tubular k-member. I am sure this was insufficient and creating other problems.

AlkyIROC

Installing a higher capacity battery isn't going to help a hot start issue. That's only a band-aid fix.

Running too hot during rounds, install a larger rad to get the heat out of the system.

FRMULA88

I have a be cool alum radiator, the biggest one you can fit in the core support, and twin fans.

If the battery cables were undersized for my 3HP starter, which draws 75 - 100 amps when cranking, the cables could build up enough resistance when hot to prevent the starter from spinning as it should.

This is exactly what I experienced; engine cold / warm it starts right up. Engine heat soaked the starter cranked over slow. The high static compression makes this worse.

Wait an hour, or jump it and it started just fine.

Common sense tells me the additional amperage while jump staring was enough to overcome the resistance in the smallish/high resistance battery cables.

I will see how it performs with the larger cables and proper grounds before I decide if I need more cranking amps.

AlkyIROC

With the battery in the stock location and the maximum your starter is drawing is only 100 amps, you want battery cables with a minimum of 4 gauge. 2 gauge is better.

DIGGLER

iTrader: (1)

what sort of ignition are you running? mine pulls timing until the engine starts to make it easier on the starter.

DIGGLER

iTrader: (1)

hes got 1 gauge cables, which should be plenty large enough for that short run down to the starter.

lil m block, 13:1 compression, and a battery up front is a pretty uncommon combination. lol some thoughts-
big battery, big radiator, big fans, lil m block = heavy
alternator trying to recharge battery after running fans and pump = parasitic drag during your pass. a spare battery with solar charger might be a neat setup for you instead of a generator. but used like a generator.
how fast is this car? ballast up front may not be needed. control that with your front shocks, springs, and/or limiters if you are doing wheelstands.

AlkyIROC

I missed the wire gauge part. I like the timing start retard. My ignition has it built in and is adjustable. I retard my timing to start the engine. Once over 500 rpm, timing goes back to full advance.

Start running heat shields. Wrap the starter and cables with some insulation to isolate the heat.

You have something seriously wrong if you can't start a hot engine with an OEM sized battery even after running the fans and pump in the pits.

Switch to a CS style alternator if you're not already using one and if you have to run the fans and pump for a long period of time in the pits, use a battery charger/generator. If you're making that much heat that you need excessive time to cool it all down then your cooling system isn't doing a good enough job.

Pull the thermostat out if you have to. It's only job is to maintain a minimum heat. Once it's open, it's open and does nothing if the coolant temperature doesn't go below the opening temperature. Running the pump in the pits with a thermostat won't allow proper flow because the thermostat will close and limit flow to the rad. If an open thermostat opening allows too much flow through the system which can be just as bad as not enough flow, install restrictor disks in place of the thermostat.

FRMULA88

Problem solved !

The solution: new 1 ga battery cables.
battery - cable grounded to chassis.
battery + ran to starter. I also covered the + cable with heat wrap.

4 ga ground strap from right cylinder head to chassis.
0/1 ground strap from left side of block to chassis.
All test done with my same group 75 battery.

I am now getting over 14V to the battery from the alternator with both fans running.
readings at the track were mid 13v range.
My alternator is the CS series, I had the front case changed to the 12 & 6 o-clock mounting ears at a local alternator shop.
it's a 105 amp model (stock size for a 3rd gen)

The engine restarted every time today with no signs of the previous symptoms
I even after let the primary fan run for 7 minutes (to drain the battery) she fired right up without hesitation.

my previous paths to ground was non existent. just the #4 - cable fastened to the motor mount.

FRMULA88

some pics to show what I did.

I had no ground straps before.

All hardware for the cables and grounds is stainless steel
I even made some stainless 3/8-16 studs using carriage bolts ( I cut the heads off) to connect the side post terminals to the battery.

FRMULA88

alum heads, & intake, tubular k-member & a-arms, manual steering and brakes. no A/C or heater. fiberglass hood. my battery weighs 33 #

Dynalite front brakes on my wish list...

Any parasitic loss from the alternator is negligible, as far as I'm concerned. This is an old wives tale from the 1950s

LOL why not just run a magneto.. If I want to go to cruise in I can with no worries.. plus I still have stereo in it LOL !

AlkyIROC

At full load, you may lose 2-5 hp but it's unlikely you'll never see the alternator working at full load. It's always better to run an alternator unless it's physically impossible to install one. I mounted mine backwards to get it to fit. Any electronics in the car, especially modern ignition systems, need good voltage. Running without an alternator starts to drop the voltage too low for the electronics to work properly.

DIGGLER

iTrader: (1)

It's not a wives tale at all. If you drain the battery down very low, the alternator is going to be loaded heavily trying to get voltage up to 13.8. How many horsepower will it take? I don't know. I wasn't suggesting you run without an alternator, I was suggesting you use a generator or something other than the car battery Between rounds.

FRMULA88

The alternator only has two jobs:

Provide power to all accessories when the engine is on.
Charge the battery when the engine is on.

A properly installed alternator should be putting out over 14V to the battery with a load ( accessories on ) at idle.

Prior to properly grounding my system I was only seeing 13.8V. I would take a very educated guess that the battery was not getting charged and who knows what was going with the accessories.

It is an Old wives tale indeed..

A '15 Hellfire makes over 700 HP and you can drive that car anywhere with the A/C on too LOL.

FRMULA88

Yes, thank you.. I have always used one.

I also run a mechanical water pump (Since this was a street car) but I may switch this to an electric model, now that I solved my problem, to free up 2-5 hp that the mechanical pump may be robbing me. LOL

The nice thing is I can abandon the notion of needing a larger battery.

DIGGLER

iTrader: (1)

an alternator requires engine power to produce electrical energy. point blank period. if the starter takes 100 amps to turn the engine over, think about how much power the engine needs to turn the alternator to the tune of 100 amps (which could be possible if your battery is nearly dead and have alot of accessories.)

again, does it matter to you? probably not. but it is sucking some hp if you are draining the battery between rounds. if you told a pro stock team they could pick up 5hp they would be all ears, but a mom driving a minivan wouldnt care.

glad you got everything straightened out.

AlkyIROC

Prostock is probably running a 16v battery for the starter. Very common in the racing world and not a cheap system to use.

FRMULA88

yes, some are even using 24V

DIGGLER

iTrader: (1)

you guys are completely missing my point. completely.

FRMULA88

Point taken, but understand before I replaced the engine (and lost my grounds) I never had issues with re-starting.

The .001 to .01 of a second it cost me to run an alternator seems pointless to not use one because the benefits far outweigh any actual or perceived decrease in performance.

I bracket / index / fun race. I strive to run the best number possible as I am still tuning this new combo, but the goal is consistency so the number is what it is as long as it is repeatable.

A fistful of 10.5s time-slips is pretty darn consistent if you ask me (and that was with a poorly grounded system)
Now that I got this sorted out I can concentrate on tuning.

DIGGLER

iTrader: (1)

I don't think you understand what I was suggesting. I was saying that since you are wanting to run your fans and water pump between rounds you could either power them with a separate battery or generator that stays in the pit. If you drain the car's battery enough between rounds, the alternator will be putting out max amps during your passes. I wasn't suggesting you remove your alternator whatsoever.

FRMULA88

I understand, but I prefer to travel light so one less thing to haul to the track is good. When you don't have a stacker trailer and a full arsenal of
snap-on tools cargo space is limited to what I can fit in my SUV.

By the time I drive to the staging lanes, into the burnout box, etc. the battery will have ample time to recharge even if I take it down to 50% capacity.
I did this by running the fan for 7 minutes, which is an extreme example.
The car restarted with no hesitation.

My 12 amp battery charger brought it back to 100% in less than 30 minutes.
I imagine my 105 amp alternator even at 50% capacity will do it in a fraction of that time.

I get what you are saying, maybe one of these 40watt folding solar panel battery chargers would be cool just in case.
In the pits I can set on the roof and plug it into my battery between rounds. plus it takes up little space.

Scorpner

iTrader: (4)

FWIW, neither the alt or battery were designed to be repeatedly charged to that extreme on a regular basis. One alternative is to use the tow vehicle's battery or even run an isolator to a secondary battery for that purpose. The secondary battery could be a larger deep cycle battery designed more for running down as mentioned.

DIGGLER

iTrader: (1)

Fwiw, I have used my cars battery in the pits exactly like you are doing, but I was heating my nitrous bottles. I noticed my alternator belt wanted to squeel as I drove to the lanes and even when doing my burnout sometimes. Belt was tensioned pretty good, but was a 4 rib serpentine which wasnt ideal. 100a alternator. Anyways, it got me to thinking, and I started hooking onto my tow vehicle for power. Side benefit to that was I never drained the battery too far and the car always started. Lol.

FRMULA88

my situation was made worse because I had no ground straps..

The battery still had plenty of juice at the track it just was not getting to the starter.