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Info needed on 86 Diesel

Discussion in 'The Garage' started by Eric W, Oct 30, 2006.

  1. Eric W

    Eric W Registered Member

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    ...have the opportunity to purchase a 86 Diesel. I'm still getting some more info on it, but the seller says it is a D10 Military version. I looked at the specs page and did some searching on it, but could not come up with too much. I noticed there are two different diesel engines offered, both the 6.2 L with 130 or 148 HP.

    I've done research on the 86's before but mostly for the gas engine. I need to know all there is to know about the diesels.
    How are these engines? This is going to be a complete project/beater vehicle but I'd still like to cruise around town on those lazy summer days with the top removed. How is the power compared to the gas versions? Efficiency etc?
     
  2. rx7gslse

    rx7gslse 1/2 ton status

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  3. jdemaris

    jdemaris Registered Member

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    The horsepower differences are based on a few small internal differences including fuel delivery, valve sizes, type of precombustion chambers used, etc. I've had all variations and not noticed much difference in regard to power. The HD engine has smaller exhaust valves then the LD- mostly to prevent head cracking. HD also has less emissions stuff and a slightly different intake manifold.
    I can guarantee you - that if you search - you will find plenty of good information and also lots of BS. So, good luck sorting through it. Here's my two cents.

    I've been driving and working on 6.2s since they came out and I still have over a dozen. I've also worked as a diesel and injection pump technician for 40 years. That does not make me a genius - but I do have some experience.

    General Motors - during the late 70s - after having many problems with their 350 diesels that were designed and built in the Oldsmobile plant - hired Detroit Diesel Corp. to design the 6.2. It was intended to be an equivalent to the 305 gas engine in horsepower and torque - but can get almost twice the fuel mileage. The first year is supposed to be the best block they ever made - 1982. That because of the high nickel content. There have been reports of some military blocks also having high nickel - but who knows? I don't. During the later 80s, there were some weak 6.2 castings that tend to crack around the main bearing webs - usually #2, #3, and #4. When they finally let loose the crankshaft will break to pieces. Of my own vehicles, I've only had one do it - my 87 Suburban and it had over 500K miles when it happened. I know of others that did it at a little over 100K.
    Again - in regard to power - just about equal to a 305 gas - except the diesel will give better torque at lower RPMs. Fuel effiency is overall pretty good - better than most later diesels except the Cummins. You can expect 16 MPG around-town driving in a Blazer or 1/2 ton pickup, and around 13 in a 4WD 3/4 Surburban. I've driven a few military 1 tons that got around 16 MPG at highway speed. The best I ever got was with my 82 1/2 ton 4WD pickup with overdrive manual trans (four speed). It has gotten 24 MPG. My K5 Blazers with overdrive automatics and 3.08 axles can get up to 23 MPG, my k5 Blazers with T400 trans (no overdrive) and 3.08s get up to 21 MPG, my 86 3/4 ton 4WD Suburban and 89 GMC 3/4 ton 4WD Suburban - both with T400s and 3.73 gears can get a best of 19 MPG - but that's rare - the usual for highway driving is 17-18 MPG. The key issue with a diesel and fuel mileage is - it does its best in at the peak of its torque curve- and after you pass that curve - mileage drops off at a faster rate than a gas engine. The 6.2 makes peak torque at 1800 RPM.
     
  4. uglytruk

    uglytruk 1/2 ton status

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    Great notes. What's my 6.2 4.10's TH400 spinning at 65 mph?
    Next kwestion: If I rebuild a '95 6.5, can I fit the 6.2 stuff to it? Like V belts? Old style, remember? A friend gave me one with 175k hard miles, but the cylinders have NO ridge. And I've got this "dead" '86-6.2 that prob has a broken crank or sumthing? The heads should be good, (150k) they'll be serviced by the local machine shop. Should I get new pre-combustion chambers? What are those things, anyways?
     

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