I have that problem right now. It started last year, I think I might have damaged the "O" ring when I had the distributor out to prime the oil pump after setting for the winter.
Spoke to MSD and they set me out a new "O" at no charge. One of the last projects to do before firing up this "Summer" weekend! Supposed to be in the high 80's!!!

Alan thanks for the rear sway bar kit, went in like a dream, real easy!!!