Classic/Antique Car Repair: Smoky 283 v8, wt oil, valve seals

Question
Got a 1963 283 v8 in a 1957 GMC truck, Brought it and it ran like a pig probally not serviced for years and smoked alot, Done plugs, leads, filters etc timing, mixture runs like a dream but still smoky( the exhaust if you take your foot of the gas the press the gas ! is this draw throu from valve seats or rings?)
Compression test has 110psi - 118psi on all cylinders
Also on idle when hot you can see gasses coming out the breather valve in the rocker covers.

advice please
Mark


Answer
Mark;
  Hi - a 283  thats a good motor ,  you have good cyld. psi . but I bet that the valve seals are bad ,  you can try to change the oil and filter -use 30 wt. oil and add a can of stp  and look in the auto shops for a can of valve seal fixer , doing this might just help it out and it can't hurt. ok and you can also get some hotter spark plugs to burn more of the oil .