Stuck valve likely but I'm saying that because it is all I can think of. Test for that by removing the rockers and pushrods and smacking the tops of the valve stems with a brass or plastic hammer. You'll soon know if you have a stuck or bent valve. If the heads are off do it on a bench. 

Jim

Sent from my iPad

> On Dec 31, 2015, at 4:30 AM, John Rodgers <jrodgers113@GMAIL.COM> wrote:
> 
> Engine turns beautifully by hand on the bench. Put the new AMC hesds on
> with all parts assembled, torque them down,  and the beenengine won't turn.
> 
> Removed the heads twice, still no joy. Sounds like a valve stuck in a guide
> to me.
> 
> Any body else ever had this problem or got an educated opinion?
> 
> Thanks.
> 
> John