I disassembled my 318 Magnum and
found this on the rear main [see pix,
below -Ed.], is this a casting flaw or did
something bad happen? I know it has a
small hole, but I have never seen a rear
main with a hole that big, is it safe to
reuse?
main bearing cap on his Magnum mill. Not
good, not good at all.
It is difficult to tell from the photo with
any certainty, but to me it looks like an
OEM defect (foundry flaw). I don’t like it
one bit, I’d certainly not use it in any performance
application. Since you didn’t
mention any kind of failure associated
with the defect, I have to assume that the
engine ran OK, so, maybe for a deadstock
rebuild, put on dark sunglasses
and bolt it together.
Problem: It will cost more to fix this
properly (find another cap, mill it undersize,
then align-bore the block) than a
complete core engine would cost. Me?
I’d have a 360 in there ASAP. Note that
the cap is marked “360”, that’s because
the rear main seal area on 318 Magnums
was increased in diameter to be common with 360s.