Solved

 

Any knowledge to pass on?

 

Find the swirl port spark timing map and have someone burn it on a chip accordingly. They have a high burn rate I'm sure you know the swirl allows for mild timing needs. I think I have a spark timing map I found a bit ago if you need help

 

I'd really like to see it and compare to what I've built to this point.

 

It’s definitely true that the swirl heads on an otherwise stock TPI motor needs less timing advance. For many years with my car, I had detonation issues on the 2-3 up shift at wot and also would not pass the sniffer for nox emissions without retarding the timing. I could never figure out why. This was with an all stock (or so I thought) setup running 93 octane. Years later when I tore the motor down, I found that it was a 350 but not original to the car. It had an L98 cam, but also swirl heads. That finally explained the detonation and high nox emissions. From my experience with this, the stock timing needed to be retarded by about 6 degrees for the swirl heads.

Either have a new chip burned, or you could back off on the initial timing setting at the distributor.