Check said:
"Clean the contact point
on the block with sandpaper or a "dremel" type tool. Use some grease on all
terminals, and the bolt when you re-install everything. Tighten the bolt
firmly, but be careful, as these are aluminum ( and old ) threads, and will
definitely strip if too much torque is applied."

He is right on the money.  I had the same problem for about a year, before I
fixed it right.  Even after I fixed all the terminals, the bolt on the block
just plain wore out.  I ended up drilling a new hole next to it and tapping
it out, and using a new bolt with a beefy thread.  Grease down everything to
cut back corrosion.

Actually, now that I think about it, I think I used a stud set into the block
and nuts to secure the wires to it.  I think I thought it would be better to
crank it down with.  Who knows.  Just make sure it is clean.  Your engine's
brain depends on it.

Bill Marshall
85 GL Tiico "Pandora's Box"
Bradenton FL