If it's blowby a compression test will tell.
I have a 49 216 that sat 30 yrs before I got it running. I had the head refreshed but did nothing to the bottom end except break the glaze off the cyl's.
At 1st it had terrible blowby, smoke would pour out the valve cover vents. With usage it's down to practically none now. It still has blowby as evidenced by the huge amount of condensation that collects in the valve cover in cold weather. Theres none in warm weather...
In thinking I could have a coolant leak in the cyl's I added a coolant overflow tank. It not only proved I had no coolant leak but I haven't had to add any coolant to the radiator since. When hot the radiator pukes some coolant into the overflow tank and when it cools off it sucks it back. Constant monitoring has proven to loss of coolant.
Compression testers are cheap and if one likes to work on ICE's of any type it is a necessary tool to have in ones arsenal.
Good luck
Dave
