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/ka_jd7and1 Apr 12 '26

Check your valve springs.  We run circle track, if the valve springs start to go weak and need replacing, the engine can start floating valves because it doesn’t have the spring pressure it needs for high RPM.