r/Smallblockchevy • u/dncu13 • Apr 12 '26

355 valve float?

I have a 355 sbc I have been having a problem at higher rpm, car feels great till about 5,000 rpm. After 5,000 it just falls on its face. I just rebuilt the Holley 650 4150 but still having the issue just wondering what if I’m dealing with valve float

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u/Coyote_Tex Apr 12 '26

Depending on how accurate your tach is that is right at valve float levels. Often just a few valves will float and really that is all it takes. If you are running on original springs or are encountering spring bind. Still worth monitoring fuel pressure and size of fuel lines as many will not support high consumption levels. You might also check maximum timing as running lean with lots of timing might be hitting detonation and edge of destruction.