71 Duster 360 turbo build

subcom said
What are the symptoms of valve float? Does it happen under any amount of boost or only when you get up into the higher PSIs? Is this with the exhaust wide open? I noticed in my back pressure tests that my RPM was hitting a 5800-5900 ceiling when running through the muffler.

Under boost on a pull it will rev to 6000, but not beyond no matter the boost level. It does make a breaking up noise, but not popping. AFR appears about normal and timing looks good. I closed the plug gap from 30 to 22 with no change.

Driving the car slowly increasing rpm(no boost) causes it to break up at 5800. It almost sounds like the valves are hitting the pistons for that fraction of a second, but I’ve noticed no repercussions; compression check still good.

Spring pressures before install were 130 on the seat and around 330 open(.600). Advertised as 145 and 360 open(no height given).

White is rpm. 6k flatline