"The engine was a complete disaster."
"They couldnt stay running for any normal amount of miles with out blowing a head gasket or blowing the bottom end apart!"
When it comes to the 350 Diesel, these are the opinions of millions of people around the automotive world. Not a whole lot of people to this day know the reasons for the common problems of the 5.7 Diesel through out its time. Its actually a pretty simple explanation. What you are about to read, is an answer to the biggest question of all time..well at least if you where a 350 Diesel owner in the 80's. "What the Hell was the problem?" was basicly the big question..well, here is your technical answer in simplest form.
The engine has quick reaction, but builds up alot of pressure in the cylinders really fast due to the short stroke, which would be ok if the head bolts worked right. The Head Bolts, a major problem..there might as well been wing nuts made of glass to hold the heads down..For anyone who doesnt know about them, prepare to learn something. The head bolts on the 5.7 cant take it at all, especially the earlier ones..All that extreme pressure is too much for the head bolts, so some start to stretch untill they let up enough to allow the head gaskets seal to give out, sometimes the bolts would even break in half..nasty watery Diesel Fuel also helped this problem a bit..usually in either case, causing the surface of the head to go irregular..might as well just leave a bolt or two out...so now there is a warped head(s) with uneven torque..suddenly, there is bubbles in the coolant tank. So, into the shop they go for a head gasket job. After the heads come off, they are cleaned up a bit and then a new gasket is put on and of course, the head bolts that look fine (that are most likely stretched) are re installed and the broken ones are replaced with new ones. So now, what has been done here basicly is, your warped head has been cleaned up and put back on..and torqued down with streched bolts..it would be just like torquing all the bolts to differnt amounts and uneven at that..Ooops!...15K miles later, there is bubbles in the coolant tank..AGAIN...Suddenly, everyone is puzzled...Noone can figure it out, so they say "what a Bad Engine". But what really happend is, your most likely warped head that was torqued down with stretched bolts giving false readings either stretched some more which made everything even worse, and the irregular areas that where caused from the last time made it that much easier for the gasket to fail. After a while, when GM found that there was head bolts breaking in half constantly, they updated them. Well as it turned out, these werent so hot either..they pretty much had the same problem..not really breaking so much, but stretching and being reused. By the time the 1984 engines came out, they where pretty decent..and would run and run with out failure..but as soon as the injection pump timing was advanced to attempt to gain power..there was bubbles in the coolant tank shortly after..pretty much meaning that a bolt or two or five had been stretched...and then of course re used..the cycle goes on..The ones that where left alone however, seem to run on and on..but the bolts are still weak...I strongly suggest the use of ARP Head Studs (available today! Check the PARTS section for a listing)..they dont do anything but sit there and hold the head..like they are suppoesto do.
The Breaking Crankshaft and other bottom end problems..this was also do to poor fasteners..In 1981, the main bolt threads where drilled out deeper and longer bolts where used to avoid these problems..before this was done, they had the mains held in by bolts that where too short...Ooops!..what a mess that caused..In this area, I also suggest ARP Main Studs in the early engines with these shallow threads..I also use them on the later engines as well..it cant hurt. We also must not forget the oil pump shafts breaking..another Ooops...There are superior strength ones available from high performance places. There where also other problems, usually due to the attempt to use the same light-duty type parts the gas engine did..for example: Rocker Arm Bridges. These types of problems had been pretty much covered by 1981 though. Its really not a bad engine..If you think about it (literally).