Sleeving 340 for a Stroker kit

Oldmanmopar said

What is the reason for the notch in the top of the bore prior to the sleeve?

Click to expand...

The 348 and 409 engines have cylinder heads that don't have a combustion chamber, kinda like a diesel. The chamber is the top part of the cylinder. The way it's designed, it has to have a valve relief in the block.
Here's Edelbrock's version. The stock one is similar.


Here's a shot of the chambers in the block. You can see the reliefs for the exhaust valves.