darlandz

okay so i got a 95 z28 and i was driving medium hard after a fresh rebuild and i was driving back home from the gas station and i gave it a fair amount of pedal and then i hear this tingy metal sound. so i start taking it apart.. thinking maybe roller rockers are adjusted wrong or something then i take off the left side and i get to six intake and i pull off the rocker and the spring just wobbles and the top of the valve is broken off right at the top of it. the valve didint fall into the piston hole and it still goes up and down. so what would have caused this? and another thing was, it was backfiring or poping what would cause that considering it has new plugs, 10.4 wires with fireproof covering near the headers and a new accel optispark and a new accel coil. so help me out with those two questions. thanks

hotrod18_69

What springs are they?

cnorton

I'd say that your analysis of a "problem" with that valve is pretty accurate. Valves do break at that point although, fortunately it's not a common thing in my experience. There's practically no chance that the valve didn't drop down at least once and tag the piston (the "tinging" sound). The popping and backfiring were caused by that valve being hung partly open during the combustion process. If you're extraordinarily lucky, the piston might not be damaged. Meanwhile, don't fire it up again and get the head off so that you can see how bad it really is. Best case scenario is that you'll need a new valve. Worst case could involve things like a new piston, damage to the cylinder wall, and/or damage to the head. The extent of damage may be relative to the number of times the engine rotated after the valve snapped off. Check for coolant in the pan as an indicator of a broken wall or a broken head.

Good luck

Stl94LT1

Sounds like severe coil bind. I hope you weren't running stock springs with the Hotcam?