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Thread: Engine meltdown disaster

  1. #41
    DonTom
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    Re: Engine meltdown disaster

    "and running it at 4,000 rpms all day would kill it as quickly as a small block, and maybe quicker."

    IYO, what would be a safe RPM range to run all day on that 400 in an 11,100 LB RV? And with an OD tranny, would it even go 75- 80 MPH without lugging the engine?

    -Don-





  2. #42
    DonTom
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    Re: Engine meltdown disaster

    "In an RV, you are much better off with a new engine."

    I know, but I couldn't then get a new 400 and all the new 350's were for light duty.

    -Don-




  3. #43
    Vulture of The Western World Eric's Avatar
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    Re: Engine meltdown disaster

    [quote=DonTom ]
    "and running it at 4,000 rpms all day would kill it as quickly as a small block, and maybe quicker."

    IYO, what would be a safe RPM range to run all day on that 400 in an 11,100 LB RV? And with an OD tranny, would it even go 75- 80 MPH without lugging the engine?

    -Don-



    /quote]

    Assuming adequate power for the weight of the vehicle, with proper gearing and an OD transmission you should not be seeing more than 3,000 RPM at 75-80 mph. Ideally, under 3,000 and closer to 2,500 RPM at steady-state cruise.

  4. #44
    DonTom
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    Re: Engine meltdown disaster

    "Assuming adequate power for the weight of the vehicle, with proper gearing and an OD transmission you should not be seeing more than 3,000 RPM at 75-80 mph. Ideally, under 3,000 and closer to 2,500 RPM at steady-state cruise."

    But that's a lot to assume. I am not so sure if the 400 would have enough power to even get up to 75 MPH below 3,000 RPM's.

    I had a rod break in a 3/4 ton van, which had a 305 and ran at very low RPM's. It was rather gutless, but it ran fine on level ground.

    I have to wonder if rods break more often in GM small blocks than in any other engine, regardless of RPM's.

    But we were tough on that RV engine during that last trip, driving more than 75 MPH for most of the day. But I didn't think 4,000 RPM's was too much. It felt fine at those RPM's until the meltdown.

    -Don-



  5. #45
    Vulture of The Western World Eric's Avatar
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    Re: Engine meltdown disaster

    "But I didn't think 4,000 RPM's was too much. It felt fine at those RPM's until the meltdown."

    Continuous operation of any non-HD (heavy duty) or high-performance GM small block from that era ('70s) at 4,000 RPM is almost begging for major problems and an early demise. The stock blocks during that era were not the best; the rods were mediocre. Most of those engines (and rods) had redlines just over 5,000 RPM (if that), so you can imagine the loads you were placing on the internals. Only a few engines of the period (Pontiac SD-455, Chevy L-82 350, etc.) were built to handle higher RPM and sustained high speeds/loads. These engines had tougher blocks (better material; reinforced areas, etc.) as well as HD rods designed to handle abuse.

    Newer Chevy V-8s (Vortec and LT-1/LS series) are probably much tougher.

    But even so, I personally would not run one at 4,000 continuously and expect it to live long.

    With a modern OD transmission, though, this ought not to be an issue. I drive new vehicles of all kinds and none of the V-8 powered ones has a cruise (70-75 MPH) RPM much over 2,500 RPM (if that; usually, it's lower).

    Even my Trans-Am (a heavy car with an aggressive 3.90 rear axle) lopes along at just over 2,000 RPM in OD at 70 mph...

  6. #46
    DonTom
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    Re: Engine meltdown disaster

    "I drive new vehicles of all kinds and none of the V-8 powered ones has a cruise (70-75 MPH) RPM much over 2,500 RPM (if that; usually, it's lower)."

    Even those that weight in at above 11,000 lbs? BTW, I hear the newer RVs are lighter at the same size. I think there might be more to it than just the high RPM's, since I had a rod break in my 1984 Chevy 3/4 ton van too, which ran at very low RPM's.

    But I guess it's no longer an issue, as I will most likely never have a GM engine from that era again--at least not in a RV.

    We usually get a lot of miles out of of our vehicles, such as tha Oldsmobile V-6 that almost made it to 400,000 miles before the first engine problem. That's the only engine I have driven long enough to experience low oil pressure (at around 385.000 miles). That's when we junked it. We have had the worse luck with the GM V-8 small blocks. Those are the only engines we've blown rods in.

    -Don-

  7. #47
    Senior Member misterdecibel's Avatar
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    Re: Engine meltdown disaster

    Gotta say, doing 80 MPH all day in an RV was begging for trouble. Especially in the summer.

  8. #48
    DonTom
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    Re: Engine meltdown disaster

    "Gotta say, doing 80 MPH all day in an RV was begging for trouble. Especially in the summer."

    Well, I should have realized we were overdoing it when it was eating a quart per day above 75 MPH, but almost no oil when we had to go lower speeds. No doubt we were very tough on the engine during that trip. We climbed many mountains to above 11,000 feet. I didn't know that there were so many freeways and highways in Colorado that went to that elevation -- no matter which way you cross the state. We also didn't know so many states had a 75 MPH interstate freeway speed limit, even the Eastern part of this state (NV).

    And it was over 100F for most of that trip, 107 in Dodge, KS was the high. But the coolant temperature never got more than half way up the scale. There was no sign of overheating at anytime during the trip ( other than the ECM problem I mentioned in the fist message in this thread, which is in the cab). It has a very large radiator.

    -Don-

  9. #49
    DonTom
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    Re: Engine meltdown disaster

    "Gotta say, doing 80 MPH all day in an RV was begging for trouble. Especially in the summer."

    I forgot to mention that we had a couple of larger, newer RV pass us, one that was towing a car, when we were doing above 75 MPH.

    -Don-


  10. #50
    Vulture of The Western World Eric's Avatar
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    Re: Engine meltdown disaster

    "Even those that weight in at above 11,000 lbs? "


    Well, not quite that heavy - but close to it. For example, I recently had a huge GMC Sierra 2500 Quad Cab 4x4 truck; had to weigh at least 6,000 pounds,if not more. And like most any modern vehicle with an OD transmission, at 70-75 its engine was turning not much faster than a fast idle.


  11. #51
    mrblanche
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    Re: Engine meltdown disaster

    I have towed my T to our national meet the last 3 years. In my Ford F150 (4.6 litre, towing package), I cruise on the highway at somewhere around 2,000 (that's at a legal speed). On a hill, first the converter clutch unlocks (+200 rpm), then it downshifts to third, then on a hard pull, even down to 2nd. That's 4500 rpm at 60 mph! It sounds bad, but it doesn't seem to do any damage.

    So, Don ran his RV at what was essentilly a low gear in most modern vehicles.

  12. #52
    DonTom
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    Re: Engine meltdown disaster

    "So, Don ran his RV at what was essentilly a low gear in most modern vehicles."

    I assumed it was geared so low because of its weight. But it might also be because of the 55 MPH speed limit when that thing was built. So we were going all day and half the night at 20 MPH faster than it was designed for. The speedometer pins at 80 MPH, but I checked the true speed on my GPS. We were averaging close to 80, which is the speed of most of the other traffic where the speed limit is 75 MPH. The higher speed limits is what blew out my engine! We never would have went that fast if the speed limit was still 55 MPH! Does this mean we can blame Gail for raising the speed limits? ;D

    -Don-


  13. #53
    Senior Member misterdecibel's Avatar
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    Re: Engine meltdown disaster

    So did I understand correctly that you just gave the hulk to your mechanic?

    Will a proper post-mortem be done, or is there even any point in tearing down a seized engine that will just be replaced by another whole engine anyway?

  14. #54
    DonTom
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    Re: Engine meltdown disaster

    "So did I understand correctly that you just gave the hulk to your mechanic?"

    Yep.

    "Will a proper post-mortem be done, or is there even any point in tearing down a seized engine that will just be replaced by another whole engine anyway?"

    I have no idea what he will do with it. He does sell used vehicles too, so he might fix it up for the next poor sucker.

    In the next two years or so, we will be deciding what type of RV to buy. Only things for sure at this point is that it will be a Class A, less than 25 feet long, and later than year 2000.

    Is that smog junk they put in diesels after 2007 sort of like what they did with the early 1980 vehicles? IOW, they just added the junk on vehicles that really were not designed for it, and caused more problems than anything else. My 1984 GM van 3/4 ton van had so many hoses that it was difficult to find the engine under them!

    -Don-

  15. #55
    MikeHalloran
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    Re: Engine meltdown disaster

    The Diesel emissions junk is in about the same state that gasoline emission control was in, in about 1972.

    No, make that worse; you have to add urea regularly.

    And no, you can't just piss in the urea tank ... but you'll want to.


  16. #56
    Senior Member misterdecibel's Avatar
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    Re: Engine meltdown disaster

    What does "Class A" mean?

  17. #57
    DonTom
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    Re: Engine meltdown disaster

    "What does "Class A" mean?"

    See message 28 in this thread.

    -Don-

  18. #58
    DonTom
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    Re: Engine meltdown disaster

    Does Diesel fuel go bad faster or slower than gasoline? Is it still usable after a year just as gasoline usually is ?

    -Don-


  19. #59
    mrblanche
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    Re: Engine meltdown disaster

    Quote Originally Posted by MikeHalloran
    The Diesel emissions junk is in about the same state that gasoline emission control was in, in about 1972.

    No, make that worse; you have to add urea regularly.

    And no, you can't just piss in the urea tank ... but you'll want to.

    Not yet, you don't. Maybe in 2010; the jury is still out.

    Don't get anything after 2006. The new engines DO have self-regenerating particulate traps and converters.

  20. #60
    MikeHalloran
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    Re: Engine meltdown disaster

    Quote Originally Posted by mrblanche
    Don't get anything after 2006. The new engines DO have self-regenerating particulate traps and converters.
    Agreed about 2006.

    I've installed self- regenerating particulate traps and converters in generators for big yachts (engines about the same size as in your truck).

    They were not required at the time; the owners (people of whom you've heard) wanted to be perceived as environmentally responsible, and spent amazing amounts of money in that pursuit.

    In the constant high load service typical of a big yacht's genset, the converters should have worked great, and were so advertised ... but didn't come with a performance guarantee. The traps clogged, repeatedly, and had to be manually cleaned, repeatedly. When the crews threatened to mutiny, they were cleaned thoroughly and deposited at the bottom of an anonymous body of water. They should make nice fish habitat.

    The people who sold the converters were very smart, and very knowledgeable about catalysis; demonstrably less so about engineering, and Diesels. With money, technical help, and especially pressure and production volume, from the car/truck Diesel guys, they may eventually get it right, but I don't expect it to happen soon.


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