well, something is giving me the fits for sure. I do not know why it is impossible to use a 200 shot safely on that particular LS1 although everything is right.

I have a MM kit with all the goodies, standalone fuel system, separate fuel controller, FJO, FPSS you name it. Engine runs an aggressive tune with 34 total advance and I take 11 degrees out via a timing tuner when on nitrous.

Everytime we shift from 3 to 4th (stick shift Vette) a massive backfire and something takes a dump. Pulls like crazy in first, second and third until the 3/4 shift. AF a rock steady 11.8 this time, EGT'S fine, water temp fine.

history:

engine is a stock cube LS1, forged rods, forged JE pistons and fully CNC machined LS6 heads (GPR) along a 230/232 cam at 114 LSA, headres, race cats and so on, stock injector but huge Bosch pump. Runs like a bat out of hell in NA trim.

last time we ran a bit lean and burned up an exhaust on #8 valve which might have leaked a bit on the seat. Anyway, all seats got re-finished and new valve installed. To fix the fuel distribution problem we stagger drilled fuel hole in spray bar for 6 + 5 and another step up for 8 + 7. On top of that we jetted 2 sizes up for fuel. Result AF rock steady at 11.8 to 11.9

spray is on at 3500 and off at 6100, shift light come on at 6200 and shift happens at 6300 to 6400.

this time, all fien until 3/4 shift, massive backfire and suddenly white smoke everywhere because the passengers side front freeze plug has popped out. Huuh what? Conicidence or got anything to do with the backfire?
I can not believe that a blown head gasket can cause this, there is not enough time to build such a pressure inside the head that the front freeze plug pops out!

I haven't touched car as it pissed me off at the moment. And it idles absolutely nicely.

so, why is there always a backfire on 3/4 shift adn not during any other shift?
What should I look at because something is phony albeit all checks out. I am at a loss at the moment. Or was it simply coincidence that the bloody freeze plug popped out?

BTW to all who run a 200 shot, could maybe someone send me a HPfile what you use so I can look up a few things? I do not want to load a pure NOS tune as it would take the Porsche surprise effect away on the road. That was the idea of having a timing tuner to have best of both worlds all the time.

thanks for any advise at the moment!