Oh, and this is something recent - car didn’t use to do this, per the owner. The Pontiac isn’t mine.
Remember, all this stuff is directly from GM or a reputable vendor. No installation errors, we’ve checked everything and had other people look at the car.
Which leaves only “GM SUCKS” as the remaining cause. Either they screwed up the engine or those aren’t 10:1 pistons in there.
compression test will tell you that..
I ave never had luck with crated motors from anyone. That is why that was my first suspicion. I always build my own motors, trannys, etc. I had a similar problem where a guy bought a truck with a crate motor installed. Thing kept killing starters. I tried to turn it by hand (this is with nearly 500 miles on it) and could barely turn it at the flywheel.
Tore it down and taped the crank, and it was .0005 out of spec (fat) across the board. Not a lot, but enough. Took it out and went through it and it was one of the worst jobs I had ever seen. knurled pistons, no brass guides, could still see hone marks in the cylinders... just awful work.
And this was a regional distributor of good repute...