Mystery solved. All you engines are low compression, the larger street performance cam will lower actual dynamic compression at low speeds too. What you are doing is probably ideal for your engines, but do that to a hi-comp B18B or B20E & you will hurt it. (I think the American B20B's have lower comp than others B20B's too.)

Here's the sort of timing I run:

My 142 has twin HS6 SUs, a good head, K cam & 2130cc capacity using local 3 5/8" pistons that are a bit short on compression height & an injected cars 2&1/8" exhaust. Due to the deck height being a very poor .100" of an inch it has about 9:1 compression. I set my timing to 10 degrees at idle & I have opened up the centrifugal advance until I see about 38 degrees total. It doesn't ping & runs well on the lowest octane unleaded we have. It's so insensitive that I can add in another 15 degrees & I can hardly tell the difference.

My 144 has K-Jet, a great head, K cam, 2130cc & .065" mowed off the top of the block.(some off the top of the water pump too!). It's one of my old race engines & has 11.5:1 compression. On hi-octane fuel I run it at 10 degrees at idle & I have welded up the slots in the centrifugal advance & set it to 10 degrees advance for a total of just 20. Any more than that & it makes some god awful diesel noises when you stand on it. Any less & you notice the power going away. A couple of degrees missing & I really notice it.

Back when it was a racer the long motor was the same except it had a huge cam & it had 2x 48mm Dellortos + good 4-1 headers & a good exhaust. The timing was locked at 27 degrees at idle on hi-octane, or I could sneak it up to 32 on race day with 20% toluene. I swear I can notice the timing just 1 degree out with this one.

So there's one engine like yours that could take your timing setup & 2 others that would die. The top rings would smash in to a zillion bits.

Cheers,
Paul.