Guys there are a couple different types of
oil leaks
Lets start with the rearmain seal on an FE motor. If it's a rope seal, they are designed to seep or leak at the crankshaft. This helps keep the rope from drying out and from heat and really leaking. Most of the builders here now have a 2 piece Rubber/Plastic seal for the crankshaft. Most FE's don't mark their ground any more. Installing the seal in a clean and correct way and allowing the RTV 24 hours to cure, with the rotation of the seal being 10 to 20 degrees off the flat of the block should product no leak. Rope seal will seep over time.
Blowing out a gasket, I have done this on a gm product but not on an FE motor, if you call an Shelby block a true FE motor. This was from running a 10-40
oil. I have had cork gaskets break out over time. Had an
oil fire at the last R&G. No damage just the oil hitting the headers. I run a PCV valve and breathers on the motor and have little pressure inside the motor. It just cracked out from age. Mechanic got cheap and reused 1 too many times.
If you blow out a gasket in a low pressure area, your motor is failing or your pcv or valve cover breathers are not working. Some guys are running vacuum pump systems the will not allow pressure to build up in a motor. Dry sump systems work the same way with less vacuum building up in the motor. A gasket that is weak to seal could get sucked in.
Bottom line is proper assembly, clean area, and I use HI-tac on all my motors and the basic cheap old Fel-pro master gasket set. The gray RTV for all sealing corners. Last note is warning up a motor before driving it on the street or track hard. If I took out my motor with running about 130 psi oil pressure it could do some damage, blow a gasket, or break the oil pump drive or distibutor gear.
I run rolleta 15-40. I do get a leak at the rear main seal because I run 1.5 quarts over fill and it leaks out when the motor is not running. level drops with motor turning and leak stops. I go a season before changing oil. My whole system with lines, accusump, oil pan hold just under 13 quarts. Run a Fram oil filter. That's it. Rick L.