Something key to know and state.. is what cid engine and what fasteners did you use?
318/273 use less torque on the heads and fasteners can play a part in heat cycled clamping force. So less torque, less clamp, less clamp, less crush...
The same gasket used on a 360 crushed @.046 ,stock heat cycled bolts.
There's 10 lbs diff between 318 &340/360LA and even more for magnums, 114 or something near. So in order to give useful advice we need to add a description tag to our contributions of what and where and how
CID? Fastener?
