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I pulled the heads off the 460 this morning in an attempt to see what made the pushrod bend so dramatically on #1. I think that I found the culprit!! Looks like the intake valve on #1 & #3 have been tap dancing on the piston. I'm getting this motor rebuilt but.... what causes this and how would you repair it??
I'm just guessing, but I'd assume, provided everything was factory, something was sticking (valve, spring, etc) and causing the valves to hang open enough to get hit by the piston.
I've heard that installing a cam with enough lift and using factory pistons can cause the valves to hit the pistons if you don't modify them (cut reliefs in the pistons).
Having said that, it's odd that it only happened on a couple of valves. You'll probably have to replace those valves in the head, they may look ok, but the stems could be bent.
That looks like a piece of the head gasket on the piston.
That it does! If not HG material, sure looks like something dropped through intake into cylinder & got smootered between the piston & valve.
Maybe just how the photo looks?
Have you pulled the timing cover? You'll probably find the teeth on the camshaft gear have sheared off, and the camshaft isn't rotating. If the camshaft ain't turning, then some valves are gonna stay open, and pistons will slam into them. Bending pushrods, valve stems, and valve guides. Ask me how I know.
Have you pulled the timing cover? You'll probably find the teeth on the camshaft gear have sheared off, and the camshaft isn't rotating. If the camshaft ain't turning, then some valves are gonna stay open, and pistons will slam into them. Bending pushrods, valve stems, and valve guides. Ask me how I know.
I have not but I will... it's going in for a rebuild in January so I'm just exploring and learning.
I have not but I will... it's going in for a rebuild in January so I'm just exploring and learning.
How much cranking did you do, trying to get it started? Did you see any oil in the intake manifold?
If you're planning to reuse the factory connecting rods, check those really well. Especially the rods for the pistons that struck valves. Depending on how hard, and how many times the pistons hit the open valves, the rods and rod journals could be tweaked.
Keep us posted. Good luck. And Happy Birthday again!
How bent were the pushrods? Clean off the mark on the piston and see how deep it is. If it’s fairly deep, then the valve hit the piston. If it’s just a slight mark, then something probably got pinched in there like a gasket as was previously mentioned.
Im not sure about the 460, but my 302 stock cam gear had plasic on the teeth. It had mostly broken off and that allowed a ton of play in the chain which could cause cam timing issues. The cam still turned but was 30 degrees off at some points.
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You'll probably have to replace those valves in the head, they may look ok, but the stems could be bent.
