Technical Odyssey pc680 woes.

Upon suggestions from here I put a pc680 in my t bucket. Now that I'm trying to fire it for the first time I'm wondering how bad of a decision I made.
It doesn't have the umph to hit the starter on my mild 350 and spin it over. Battery shows 12 volts. Hit the starter 2 or 3 times and it's down to 8 or lower.

Did I get a dud? Is this not going to be enough to run my car? Suggestions?
Car is 99% done, really dont want to go cutting a hole in it for a new bugger battery (and rerouting all my electeical!)

 

I have a Odyssey PC 680 in my car and it has never given me a problem even after sitting for extended periods of time. If it is only showing 12 volts it is not fully charged. It should be showing somewhere between 12.6 and 12.9 volts. How long has it sit? Has it been charged? If it is new it is probably defective. I have charged mine using a BatteryTender.

 

Check your battery cable connections. Is the ground cable getting a good connection?

 

I had one and I was not impressed. It's on the garage floor if you want it.