AwesomeAuto

I take it you dont know what happens when you overdwell the coils? They fire once they are charged. Even half a millisecond too much is a LOT of timing advance. Blindly saying "just add 2 ms" is extremely haphazard.

Dont force others to make one of your constant rookie mistakes.

jayyyw

I ran B9EFS plugs at 18psi. I don't think the plugs are the issue here. Depending on what lifters he is running, his exhaust preload seems a touch low.

LilJayV10

iTrader: (39)

You know what would be great.............

A ******* tune and log..........

BCNUL8R

iTrader: (2)

Seeing a good log and tune would be good just to make sure there isn't anything there before tearing into the motor, but... I've seen a close friend go through this exact same thing. Similar cubic inches (408), similar power goals, and same issue. He ended up fixing this issue and making 1200 rwhp at 23 psi before pushing water when timing was above 16 even though there was no detonation.

Anyway...the OP is following the same process of trouble shooting my friend did eliminating things in pretty much the same order. What he found was that in some boosted setups ESPECIALLY ONES USING LARGER VALVES like the OP he needed more valve spring than expected. He also changed cam design to a less aggressive ramp rate at the same time as he did valve springs whether that was actually needed or not we don't know. After doing valve springs the issue was eliminated.

455GTO

iTrader: (18)

Issue FIXED!!!

It ended up being the crank sensor as I expected... BUT why the crank sensor? Well, my block was painted black by the machine shop and turns out the paint they used is some thick stuff and it was just thick enough that it prevented the sensor from fully seating in the bore. It wasn’t caked on by any means but just enough to make it not read at high rpm...! I sanded the paint off the sensor area, popped in a new sensor and took it for a spin and what do you know... revs to 7k as it should. I replaced my entire engine harness and so many other things just for it to be the damn paint causing the issue. I found A thread where a guy had rust on his block, especially in the crank sensor area and he ended up grinding it off and it fixed his crank signal issue so that is what got me thinking to do the same to mine.

ddnspider

iTrader: (26)

Wow that's wild, nice fix!

455GTO

iTrader: (18)

This was such a nightmare and Ive come to realize the crank sensors on these cars are so sensitive. Like i said i had a similar issue 4 years ago on a different motor but was just the sensor and it would breakup at 6300... everyone thought spark or tune but no, just losing crank signal