cylinder loading, Compression Test On 454??

I have a 454 in my T-bucket that has been fine for 26,000+ miles till lately.
I put in a Unalite distributor and got rid of the dual points. That helped out a bit but I still have a bad cylinder that loads up on the #2 plug from the front on the right side. It looks like it is oil fouled and I have replaced about 4 -5 plugs in this cylinder. I tryed a different spark plug wire and that is not it. I just did a compression check and all cylinders are 135-140 lbs.
My next thought is a bad oil seal on the valve? I know 135-140 maybe a bit low but it is getting tired from many hole shots in the past 14 years.
The problem is it pops in the exhaust as it is idling and driving slow & is very annoying to say the least. I hope it will limp along for another month or so.
Any suggestions on what I may try? I am open to anything. Thanks Gary M

 

see if the valves are opening all the way when you crank it over. Cams go bad quickly in big blocks.