I have depended on both 216 and 235 ci sixes all ny truck driving life-about fifty years so far- and found them to be the most durable and dependable engines ever built!! Expect at least 150 thousand miles before some wear begins to show up in oil use and loss of compression. It all depends on how you drive and service them. I change the oil and filter every 3,000 miles and drive a decent speed. Also regular tuneups and filter changes for air and gas is required. I think GM stopped making the 235 engines in in 62 because the lasted too long..the same for the 261 a very close kin of the 235...
