MCI 9 questions

[brando4905]

Art,

I'm no engine expert, but with a 6V71T in a MCI9 your foot would be way to far in the accelerator all the time to achieve 8mpgs. I don't think there is enough power in one of those for that bus. I have a relatively light 4905 with an 8v71 and I don't have enough power.

For what it's worth I have lost two 71 series engines in the past year. If I could have afforded a 6v92 transplant last month, I certainly would not have rebuilt my 71.

Just my cents.

Brandon

[Busted Knuckle]

Artvonne,
While I agree wit you that you've heard/read the horror stories of 92's here. I really do believe it amounts to the fact that more "new" users have them, and they aren't caring for them properly.
I also know of 71's that have and do fail! I am not trying to persuade you or anyone else to go with a 92 series over a 71. But I have been around both and it is up to me, I'd prefer the 92T series over a 71NA any day.
Of course everyone has a different opinion and all said in their own ways correct.

Now you do have a good source for reasonably priced in-framed engines not terribly far from you @ United Fleet Services in Springfield, MO. Last I heard they were running a pretty good deal on swapping out your engine for one already in-framed and ready to go.
But with today's market I'd shop around a little longer and find one running at a fair price and go that route. Just my honest opinion (not that it's worth much!)
 BK  

[Busted Knuckle]

I see Brandon posted what I was thinking while I was typing my last post!

For what it's worth I have lost two 71 series engines in the past year. If I could have afforded a 6v92 transplant last month, I certainly would not have rebuilt my 71.

I was just fixing to research and make sure my facts were correct b4 posting it!
  BK 

[luvrbus]

Somebody is pulling the chain here the 6v71 had to be the worst of 71 series ever made try cooling that puppy, 6L71 or the 8v71 are ok but if you think you are going to get good mileage out 6v71 forget that 71 series have their share of problems also but they will run longer needing repairs sometimes but don't bank on that they will pull a liner faster than a 92 series that doesn't happen often on a 92 series you get 71 series hot  they blow just as fast and the 71 series really don't like the taste of antifreeze either fwiw you are not going to get any more power from a 6v71 than you will from 6L71.
210 will not destroy a 92 that is were the shut down is set a steady diet will same with 71 series 


good luck

[CrabbyMilton]

Imagine how nice a 6-92 would have been for you guys to repower your 4104's. But I must remain pragmatic for the sake of our discussion here.
You may as well just find another 6V-92 if you buy it. That way you won't have to make any drastic changes though the other engine options would probably easily snap right into place. A smaller engine like the 6v-71 or 6-71 would work but because you would be taxing it or adding more turbo boost, it would shorten the life and fuel use may be worse. You could make the an extreme and silly example. Put 4 5hp lawnmower engines on a 747. You could say that those lawnmower 5hp engines are as tough as can be but that plane would not move.  A bigger engine with less power is better than a smaller engine with more power at least that's what I was brought up to believe if the engine design is the same. Some folks have gone the 4 cycle route too with great results.

[artvonne]

    If y'all are in agreement these are good engines I'll stop worrying about it. I appologise if I picked up the wrong impression, in retrospect there are an awful lot of these things out there, and I wasnt really looking at the "big picture". As far as an overhaul, I plan to do the work myself with the engine out, regardless of what I end up with.

   How common is this broken crank thing? The seller claims he has seen "a few" in these engines. Is it a design fault, driver abuse, or a fluke? I saw a guy dump the clutch on a Peterbuilt once trying to get a trailer out of a hole, and he twisted the driveshaft right in half. I could see someone jerking a bus at low rpm if they started goosing the pedal, thats a lot of weight to jab the engine against.

   What other engine options would work in one of these that might offer better economy, without electronic's?

[robertglines1]

You can do about any engine combo but won't get the $  back unless you run it several 100,000 miles. This was a revenue coach and designed to make money. Several do the Cummings swap and are pleased with it. It's a dollar thing stock will cost you less and if you rebuild the 6V92 you will probably never wear it out.

[buswarrior]

The popular engines for the MC9 were the 8V71 or the 6V92T.

Usually in the 270/277 HP settings.

You sure don't want less power than that.

It will be difficult to see fuel economy better than 7mpg in an MC9 without an entire drive line update with complimentary gearing.

With your posts so far, I'd think you'll be happy with a fresh 6V92T for least cost and hassle, with a choice to upgrade the power as you see fit.

happy coaching!
buswarrior

[artvonne]

I'd think you'll be happy with a fresh 6V92T for least cost and hassle, with a choice to upgrade the power as you see fit.

happy coaching!
buswarrior

  What manual transmissions can be most easily be put ahead of this engine? It currently has a 5 speed, but I still dont know if that trans has a granny low. I know a little about the 7 speed thats been discussed, but not how it shifts clutchless. I would prefer a trans that can be more easily be shifted without having to use the clutch except for starting. If your all going to make me keep that 92 back there, at least give me some good tranny options, lol. No electronic's though.

[bevans6]

If you're going to change the tranny, the hard part will be figuring out the shift linkage and the clutch.  As far as choice there is enough room to put in virtually anything you want.  Someone said recently the 7 speed Eaton/Spicer was hard to shift but that it had a clutch brake.

Brian

[Busted Knuckle]

Art if you are going to change trannys and want to stick with a manual (and would like not to have to use a clutch) check out the 10 spd autoshift. (a 5 spd shifter might work as is)
I think Don Fairchild had a couple of these a while back (or had access to a couple)
Don is a great source of info, parts, and work on these old engines look him up and contact him for more info!
  BK 

Also FWIW I believe Bob Glines is putting in the 10 spd a/s and IIRC Brian Diehl has one behind his Cummins in a '96A (basically the same as a 9) give them a shout.

[luvrbus]

I see 9 speeds with 0.74 overdrive in the MCI 9 from time to time with a 6v92 my understanding the 9 speed is 29 inches long and 7 speeds are 35 inches long I don't know for sure somebody here will know.

good luck

[artvonne]

  The autoshift sounds nice, but then im back to electronics. I hate electronics and computers, sorry.

 In the manual transmission thread, several were asking which gearboxes had dog clutches vs sliding sleeves. And I appologize if I am mistaken about that. But I believe, as do some others apparently, that some particular manual gearboxes are better able to be shifted clutchless, and easier to do so, without doing harm, than others.

  And really, whats the standard 5 speed like? Anyone know the ratios?

 This air assist on the clutch, does it take off much of the load? Does it work well?

[luvrbus]

The ones I have been around in buses are

1st    7.16
2nd   3.88
3rd   2.11
4th   1.21
5th   1.00   

or close to those numbers

[artvonne]

good luck

No kidding.

  I talked to the seller again last night, but its so darn cold right now I will have to wait a few days before I will go look at it. He claims its a southern Bus and that it is rust free. If it checks out and its cheap enough.....

  I was reading the "101" website on things to inspect. If anyone has anything more to add to that list I am all ears. I have a portable compressor, but the first look I will just go peek at it and see if its worth any further interest.