Another surprise.

[Small Block Duster]

Do not use the washers for 340 and 360. They are for use on 273's and 318's to get the right thread engagement and windage tray position since the main caps are "shorter". The washers are hardened and the concave side goes toward the cap for the 273 and 318 only.

 

[Small Block Duster]

Now that makes sense. They're using the washers as spacers on engines that use the shorter bolts. That had me mystified. Thank you I appreciate it.

 

[MopaR&D]

I didn't know that either thanks @66fs