318 Magnum Dropped Valve
Studying your 318 build.
Your title says "Magnum 318", not looking like a magum engine.
It is looking like the 318 Roller Engine that came factory with the 302 Closed Chamber heads.
Also it looks like you have the replacement aftermarket 8.5 cr valve relief pistons, when the factory Roller Pistons were 9.2:1 cr flat tops. So this tells me someone has been into this engine before, possibly before your overhaul.
Used valves and valve seats have been cut recessing the valves down into the heads, and standing the valve stems up higher than stock at the valve spring tops.
So now into stock 318 roller cam or replacement higher lift roller cam, or a reground factory roller cam that equates to smaller camshaft base circles.
Leading up to valve train geometry, pushrod lengths and type of rocker shaft stamped rocker arms?
If rocker arm geometry is off it can push the tip of the valve stem back before it starts pushing it down.
All the little things off in the valve train can throw off the rocker arm to valve stem geometry, causing undue stress to parts.
Just some things to think about of why this may have happened.
Here are some comparison pics various parts.
Valves riding low in combination chamber, after reground valve job.
Factory Flat Top Pistons
For comparison, new valves Standing Up higher in a 360 chamber.
318 aftermarket 8.5 cr pistons
☆☆☆☆☆
Studying your 318 build.
Your title says "Magnum 318", not looking like a magum engine.
It is looking like the 318 Roller Engine that came factory with the 302 Closed Chamber heads.
Also it looks like you have the replacement aftermarket 8.5 cr valve relief pistons, when the factory Roller Pistons were 9.2:1 cr flat tops. So this tells me someone has been into this engine before, possibly before your overhaul.
Used valves and valve seats have been cut recessing the valves down into the heads, and standing the valve stems up higher than stock at the valve spring tops.
So now into stock 318 roller cam or replacement higher lift roller cam, or a reground factory roller cam that equates to smaller camshaft base circles.
Leading up to valve train geometry, pushrod lengths and type of rocker shaft stamped rocker arms?
If rocker arm geometry is off it can push the tip of the valve stem back before it starts pushing it down.
All the little things off in the valve train can throw off the rocker arm to valve stem geometry, causing undue stress to parts.
Just some things to think about of why this may have happened.
Here are some comparison pics various parts.
Valves riding low in combination chamber, after reground valve job.
Factory Flat Top Pistons
For comparison, new valves Standing Up higher in a 360 chamber.
318 aftermarket 8.5 cr pistons
☆☆☆☆☆