Built up a 355 with a mild cam and TPI about 2 years ago, and i've got about 9000 miles on it, i had it tuned perfectly 0 knock counts from 0rpms to 5500rpms any gear any speed...

Decided I wanted to see what it sounded like with open headers the other day and i took my exhaust down, and fired it up and hooked it up to my computer to datalog, and saw it was going lean, so i tuned it richer and took off, and i noticed that once I hit 1900rpms or higher i would get knock counts and they'd keep going up and up the faster I went.

Went home and parked it and threw my exhaust back up. Fired it up with the original tune, blms and ints perfect, took off and it happended again, knocking about 1900rpms....

No mater which gear, 1st-overdrive it'll knock above 1900rpms?

any idea what is going on???

I reduced the timing 10* and it'll keep knocking.....had the timing around 17* when I hit 1900rpms in 3rd gear and it kept knocking...

 

I thought the TPI base timing was 6 degress BTDC?

 

It is, my base timing is set @ 6*, my advanced timing around the 1900rpm in third gear is 27-28* and I had it reduced 10* to 17* and it still knocks. Meaning it's not a too much timing issue.