Trouble starting/ Battery relocate problem

​I have posted this on some LT1 pages will no luck.
96 Camaro, Lt1 stroker ect. Battery has been relocated to the rear using a 3/o welding cable to a post up front, then the same for ground to engine and to starter. Using a cheap summit cutoff switch. If the car has a semi battery (1140CA) car will start fine. If I use a ford battery that fits in the box(1040CA) it will crank like a champ but not start. Checking voltage to the front lug it drops to 8.5ish volts with the ford battery. It has ignition spark but no injector fire with a noid light and has +voltage to the injecter. I have checked all grounds on the car and to PCM numerous times. Just replaced with a new Remi LT4 starter. bypassed the cutoff switch and have ran a jumper cable from the battery to the front post. However I can put the big battery in and it will start. I have noticed it looses around 3/4 - 1 volt from the rear to the front while cranking with the ford battery. Any suggestions is appreciated. Once it starts it runs fine. It has done this since I got it back togather with the battery relocate. Sometimes you can put a charger on the battery set to engine start and it will start but not always. Any Ideas? I am out. I have grounded the battery to the Seat belt post in the rear(sanded first)

Have you ever tried it without the "cheap Summit cutoff switch" in the circuit? Does the switch get hot when you crank the engine? The Summit cheapie ($20) I saw was rated 20 amps continuous, 125 amps surge. That seems light, if that's the one you have. The Flaming River switch, which costs 5 times as much, is 250 amps continuous. Moroso Super Duty is rated 300 amps continuous. Summit also had one rated 250 amps continuous.

I don't think you mentioned the switch in the CZ28.com post.

May not have. Anyway I have tried bypassing the switch with the same result. However I went and bought a new battery this morning and it has started 3 or 4 times. Bought another Ford battery since it is the biggest that will fit in the box. i hope this fixes it.Thanks

Ok wanted to give an update. After bypassing the cut off switch, changing batteries, extra cables, grounds and a new LT4 starter I still had the trouble. Got a tune for the car and it has yet to not start since, Even if the battery is weak and is draggy cranking it will still start in a couple spins. After digging in the old tune the injectors were set on 42lb, However I have 36 lb. Now it makes sense. The PCm may have not fired the injectors enough for starting if set like this, but I may be wrong. Either way it starts and runs good now. Thanks