ok, this is a stupid Q but does anyone have any pics of a 305 block that has been ground to deshroud the valves? Are there any templates out there for it? Got a spare block lying around, figure I'd play with it some.

 

Make a template out of a head gasket.

 

If the block is naked, i'd bolt on the heads, and make them "DS" and "PS". Bolt it on with a few bolts, no gasket. Flip the engine upside down, and reach down the bore and scribe where the bore meets the head. Scribe the head. Then you can see on the head, how much to deshroud, and where. I'd deshroud the head only. If you're doing the block, do so very carefully. Or if it's a scrap block, grind the crap out of it until you hit water. Then you know how much breathing room you've got on the next block.
Just know how far up the piston is going, you really can't take much material out of the top of the bores.

 

That's pretty much the idea, to play with it some and see where it takes me. I was just hoping to see some pics of this, a lot of people talk about it but I've never actually seen pics of it.

 

You aren't likely to do any good deshrouding to the cylinder wall. As long as you have around 3/16" clearance around the valve edge, you'll be fine.

FWIW, the cylinders on my 396 were notched from the factory. Doesn't matter with 2.06" valves, but when you step up to 2.19", different story.

 

I went and looked at some pics of the 396 blocks on ebay, very interesting it looks like they took a lot of meat out in that area, over 1/8th inch.

The big Q IMHO is how much of it was added in the casting to allow them to do that, and if there's a point where it becomes a durability issue. The depth would be simple enough to figure out, as it would merely have to be less then the piston ring height, with some margin. That would be easy enough to figure out by the ridge at the top of the block.

That being said, the largest valves they put in one of these engines in an OEM configuartion is .05 radius smaller than a 1.94 valved head, so chances are that removing much more material than that would be useless or near so, and .09 with a 2.02 intake valve. By the look of it, a jig would also be dirt simple to make using 2 bolt holes for eacy cylinder for alignment.