ok ive been a 350 gas engine since ive had my 86 1/2 ton but ive been wanting to convert to a diesel for towing/mpg/the coolness factor. i was wondering if the 350 block will work for the conversion since its new with maybe 12k under its belt. im a complete newbie at the diesel world but ive seen awesome results and maybe 3 1/2 ton sierras with diesels in them. im rebuilding my truck and i want to do it the right way and i belive diesel is the way to go for me. i usually hang out over that the 73-87 boards but not a lot of diesel over there. i would love to here any ideas or suggestions that would help me along my quest.

btw my truck is a 86 gmc sierra classic, 350(originally 305), th350chd transmission, dont remember the rear end ratio, c20 arms with heavyduty coils, heavy duty leafs in the rear and stock tires.

no matter what your doing, the simplest way is to have a donor truck available. granted, sometimes that leaves you with parts that are either past their due date or getting close. but, you have something to refference by. there is a lot of different things about these diesel trucks and how they can be quite finicky, but it isn't totally imposible. I'm simply suggesting that you find an old rusty unit to grab for a few hundred and then move forward from there. when it comes to converting your fresh 350, let that thought be your last. the gas engine survives on its 8.5 +/- to 1 compression ratio. this 379 smoker runs on a 19:1 or 21:1 ratio and its built alot differently on the lower end to compensate for such. envision that compression ratio and then think about how some of these can and will run at 3600 rpm all day long. they aren't the same beast if you catch my drift. do a search for 6.2 diesel on Ebay and see what shows up. you should be able to score a donor truck to combine with yours for somewhere near a grand. maybe I'm wrong there too.


Please accept this comentary as opion rather than fact. best of luck in your venture.

I put my 1984 6.2L engine in my 1986 C30 dually that had a 350. I had to build my own wiring harness. The ignition wire will serve as your injection pump solenoid switch. I installed separate wiring and toggle switches for fast idle, fuel advance, glow plug solenoid, and fuel heater.

I use to have the 6.2 engine in my old 1970 C20 (3/4 ton) truck, but I switched engines when I bought the 1986 C30. The person that bought my C20 was real happy to get it with a 350 that had only 86K miles.

I recently converted my '75 3/4 ton from a 350 to a 6.5 N/A diesel. I had a donor suburban and there were countless parts I pilfered from the sub in order to do the conversion. Just having an engine alone would have made the project so much harder. By the way, I just did my taxes for '04 and since my truck is for work, I kept track of all the costs in order to write them off. $2,000 for the sub with approx. 70k on the engine, and another $3,000 almost in miscellaneous costs. I did have to get a clutch and flywheel -- $600+, I sprung for two brand new batteries and a new starter -- $500, and I replaced most of the gaskets, seals, water pump, etc. -- $400. But that leaves almost $1,500 in little stuff. Hard to imagine, but I just went through my reciepts, and its all there.

I still think it's a worthwhile conversion, just be prepared to be nickel and dimed like crazy.

Using the 350 block is basically what GM did with the 5.7L diesel it used in Olds and Caddys back in the 80s or whenever. That engine has about the worst reputation of any I know of.

There is a good running 6.2 complete truck for less than 1000 on the Classifide board!!!!



Course it is mine and this is 100% attempt to pimp it out!!:muahaha:

To comment on your original question, if you are asking if you could use your 350 gas engine block to convert to diesel, the answer is "NO". It is of a different configuration than the diesel blocks and, probably wouldn't stand the strain if you could manufacture the necessary heads, fuel system, etc.

The '78 - '81 GM 1/2T 2WD pickups came with the Olds 350 Deisel and were designed to increase CAFE ratings on the trucks. They were strictly lt. duty hiway cruisers. They had their share of problems and there are not too many left on the road today. Olds designed the diesel block after their gas engines to make everything easy in production.

The misconsception that it was a gas conversion is caused by the overall appearance and low reliability of the engine. It was, in fact, a totally different block, heads, crank, rotating assy, cam, etc. The only gas engine parts that were common to the diesel were the timing cover and some valve covers. Most parts were strictly "diesel". The block was cast with a deep valley to house the IP. The drive for the IP also was bolted into the block. (none on a gas engine) The common part was the motor mount holes and the bellhousing pattern. You could bolt a gas engine in place of a diesel and a diesel in place of the Olds gas engine. (Chev 350's had a different bell housing pattern) This made changing over to gas a bolt-in. Also raised the value of a used Olds 350 gas engine to astronomical highs in the mid to late '80s.