The C7 and 3126s were fine engines, they didn't leak oil IF you changed the air filters and kept the dirt out of them and the blowby down on them, seen many, and no not one or two, many with tip top maintenence last well over 800,000 in box trucks, most people tried to run the extended oil change intervals on the 325hp versions, not a good idea, they made tremondous torque for a stock engine, I've rebuilt 5 of them now, simple engine, much better piston design and structure than their competitors, and btw they ONLY blew head gaskets if some dumbass ran it with a busted CAC (number one cause of all blown turbos and head gaskets period) and burned the fire rings out, the C7 accert surpassed the DT466 in injection quality in 2004 due the use of NO egr up until 2007, yeah they had it going on until the EPA got on them in 2008.. All in all the 3216B/C7 was a fine engine, the head bolts are huge, super tight too, 330lbs tight, had a super tough bottom end, we ran them in wreckers in MI for a long time, serviced them every 10,000 miles and air filter every other oil change, ran overheads every 75,000-100,000 and kept up on the small failures, never had one pop, and this was a fleet of 15, my advice, if you can get the whole thing to communicate together go for it, people give Cat a bad rep due to poor maintenence, kinda like everybody hated the twin turbo C15s and said they were junk, using junk oil, poor maintenence, and drove them harder than hard, Cat has built alot of junk but the 3126B and C7 were decent engines up to 30,000lbs gvw everyday gvw.