Originally Posted by hammertime
My guess
1. Ground issues, take a 4 gauge wire and ground it from the block to the frame. Take a 10gauge wire run it from the head to the battery.
2. Weaker Battery, check the voltage out put and if its not 12.65 toss it for a new one
I agree with hammer, grounds are so important, also making sure you have copper cable instead of copper clad aluminum helps. Overkill in the size of the cable never hurts. I have also never seen a single battery in a bracket car do very well (overall) when cooling and running the car for several rounds. Even with a alternator it can work it past its limits. I use two batteries always and run a ground from the battery to the back of the block and I have had good success even with the Hi torque GM starters. Of course they are built by a local who cares what he puts in them too! No Auto Zone stuff here lol.