[Vwdiesel] GM V-8 diesels of the '80s

[Kurt Nolte]

I can't actually take credit for the writeup itself; like I said, I 
found someone who explained most of the problems -quite well- and have 
been using that explanation when needed.

-Kurt


Bryan Belman wrote:
> Great write up Kurt.  You know your stuff man.
>
> Thanks
>
> --- Kurt Nolte <syncronized_turbo at yahoo.co.uk> wrote:
>
>   
>> I really, really, really wish folks would stop
>> calling them "converted 
>> gas engines," because they flat out -weren't.- I
>> found someone who puts 
>> the differences, and the problems, quite plain and
>> simple, so I'm 
>> spreading this:
>>
>> --
>> The Olds diesel blocks were entirely different
>> castings. Main bearing 
>> webs are 3/4", and the main bearing journals on a
>> diesel 350 measure 3" 
>> (big-block sized) while the gasser 350s are 2.5" in
>> size. A 350 diesel 
>> crank is the only small-block crank that won't
>> directly fit in your 
>> gasser 350. Cylinder walls are 0.4" thick - a lot of
>> extra iron around 
>> the cylinders to the point where the diesel blocks
>> can be bored 0.125" 
>> over (stock = 4.057") WITHOUT sonic testing if
>> you're using a diesel 
>> block as a performance gasser buildup. Match that
>> overbore with a 425 
>> crank, and you end up with a 437 CID V-8 gasser.
>> Bore that same diesel 
>> block out to 4.25" (WITH sonic testing required),
>> match to a shaved 425 
>> crank and a 3.975 stroke to end up with 451 cubic
>> inches for a V-8 gasser.
>>
>> Head gaskets kept blowing for a variety of reasons.
>> Mainly, diesel fuel 
>> in the 70s was crap and contained a bunch of water.
>> GM built the cars 
>> without a water separator, and water would rust the
>> steel internals of 
>> the fuel system. Rusted injectors would result in
>> erratic operation. Too 
>> much fuel injected prior to TDC causes
>> "pre-ignition" and the water 
>> injected also causes some hydrolock. Water in the
>> fuel hydrolocking 
>> coupled with injection pump timing that was way out
>> of whack (from 
>> rusting of precision injection pump parts) resulted
>> in extreme cylinder 
>> pressures WAY above what GM ever designed the engine
>> for. The head 
>> gasket or head bolts were thus the weak link. If the
>> head gasket leak 
>> didn't cause major hydrolock to the point of bent
>> rods and bent 
>> crankshafts, the mechanics (untrained on diesels)
>> would REUSE the 
>> STRETCH head bolts when they just shotgunned a new
>> head gasket in the 
>> engine. I say shotgunned in that they just fired
>> random parts at the 
>> problem, and 99% of the time never diagnosed the
>> causally related 
>> problems to fix the problems with the fuel injection
>> pumps. Hence, you'd 
>> end up with multiple head gasket failures or
>> multiple head bolt failures 
>> because the mechanics would never fix the underlying
>> problems - and the 
>> hapless owners would just swing in a replacement
>> gasser engine and blame 
>> the problems on the diesel engine. These owners
>> would just never 
>> understand the causes of their problems, and they'd
>> never take the 
>> proper care necessary to prevent the problems in the
>> first place.
>> --
>>
>> The "350 Diesel" blocks are /highly desirable/ in
>> the high performance 
>> Chevy 350 world, owing to their much stronger
>> webbing and bottom end 
>> coupled with head bolt, coolant and oil holes that
>> all line up with 
>> whatever your favorite SBC head happens to be.
>> Stronger alloys, the 
>> ability to use a stronger big block crankshaft, and
>> the more robust 
>> design of the block itself all make the engine quite
>> strong.
>>
>> Weak dealer training, gas engine maintenance
>> practices, and poor quality 
>> fuel were the death of far too many 5.7 diesels. :(
>>
>> -Kurt
>>
>>
>>
>> William J Toensing wrote:
>>     
>>> I note that "Photo Bug" has a1982 Cadillac diesel.
>>>       
>> This converted Olds gas 350 GM diesel is the diesel
>> that gave diesel a bad name in the USA. However, I
>> heard the latest "GM Goodwrench" replacement diesels
>> were reliable engines but the engines came too late
>> to stem GM's bad diesel reputation. Perhaps Photo
>> Bug can share some more info on his Cad diesel &
>> what modifications, if any, he has done to make this
>> a reliable engine. If some of the others out there
>> have made some mods to make this a reliable engine,
>> please share the info. I am not looking for one of
>> these GM diesels but it is possible I might stumble
>> on one & reject one I shouldn't.
>>     
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