Anyone listen to the tappet brothers this weekend? Guy called in from Chicago with an 83 300d. Had added anti-gel in the cold weather and afterwards can started missing at lower rpm's with white smoke. Cleared up at higher rpm's but always returns at lower rpm's. Car has 125k on it. Brothers diagnosed a blown head gasket. What does everyone think? Guy said he had a coolant leak somewhere since he could see it on the ground.
I think blown headgasket's on 617's are pretty rare so I'm not confident in their diagnosis. I was thinking perhaps an injector problem of some kind.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13