Idle went nuts.

Does it look cracked ?
The head/rod are stronger than the nut.
Go ahead and have it checked, I mean.. it would be a great time to re con it if the valves are low set, sunk anyhow.You're just a drive away from a shop at this point.
Oh and think hard on if you are going to stick with a slant before dumping money into big valves and the porting to make them work.