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Author Topic: MCI 6 Model #  (Read 1429 times)
wg4t50
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« on: December 24, 2012, 06:54:31 AM »

Having a MCI7, I spent some time around charter bus operator shops, learning all I could.  Once when in Richmond (Va), at Wynn Bus, a man from Universal coach was there I guess selling something.  ANyway he was an old time MCI employee, he and I got talking about the history of MCI, the MCI 6 subject came up, he said there were 100 coaches built, and only 99 ever hit the street because the #1 unit was being hot rodded in the parking lot with the 12V-71, and it got rolled over, ending its career as a sellable unit.
Just useless info for most folks, since I built the MC7 with the 12V-71, found very interesting info.  Always felt the 7 might have been designed for the 12V as when I slipped it up the rails, it cleared everywhere by 1/2 to 3/4" around the air intake and gear case/bell housing with compressor and power steering units attached.
ALways laughed about it.
Merry Christmas
Dave M
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MCI7 20+ Yrs
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luvrbus
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« Reply #1 on: December 24, 2012, 07:32:51 AM »

There was a mining co in Nev (Freeport) that owned 3 MCI 7's combo units that were equipped with 12v71's a friend of mine owns one it looks to be a factory installed

good luck
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Ed Hackenbruch
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« Reply #2 on: December 24, 2012, 08:12:38 AM »

According to my book the 12V71 was the "typical" engine in the 6.  After the buses got sent to California from the east coast a lot of them were changed over to the 8V71 and Allison automatics.  The 15 buses that stayed in Canada kept the 12V71 and manual transmissions.
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
TomC
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« Reply #3 on: December 27, 2012, 11:30:35 AM »

What was neat about the MC6's with the original 12V-71 was the exhaust came out of the left side of the bumper through a luever. But when they were changed to the 8V-71 with Allison, they just ran the exhaust under neath.  Always love the sound of the 12V-71. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
wg4t50
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« Reply #4 on: December 27, 2012, 12:24:47 PM »

There are a few things that make me happy about the 12V, the smoothness of engine, 12power strokes per rev.  The torque off idle, you older guys recall the drive line failures when exiting parking lots, broken U Joints, drive shah, ring & pinion all from the high torque tight off I idle, the setup was not ready for that engine. It came home to me in 2nd gear in a parking lot, were forming for a run to a FMCA event at Blacksburg Va (VA Tech). Spun the wheels. OH  I got it clearly. Smiley
Dave M
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luvrbus
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« Reply #5 on: December 27, 2012, 04:36:57 PM »

Never could understand why people would use a 12v71 a NA 12v71 with 65 injectors will get 475 hp with 1290 lbs of torque with a lot of fuel why not a 8v92TA  with 500 hp and 1550 lbs of torque on less fuel ?
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« Reply #6 on: December 27, 2012, 05:10:30 PM »

Because at the time, turbos were not very common, and fuel was cheap.

Jc
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JC
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1977 MC5C, 6V92/HT740
wg4t50
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« Reply #7 on: December 28, 2012, 01:46:31 AM »

There is no class to a 8V-92, yes it does make good hp, just no class where the 12V is an experience and I do remember before the 92 was made, all you had was the 71 or the 110 series, the 53 series was never much interest to me after the 4-73 in my F250 1971 Ford, (nother event), but the smoothness like an electric motor makes the 12V a winner to me.
The only two negative sides are the weight and fuel burn, 5.9 mpg when I checked after running flat land, never wanted to know what it was in the mtns.  Made many trips and after 2000 mile trip, oil useage was maybe half a quart at most.
Like the old story, if you are too young to remember them, does not make it a poor engine and the yaking about oil leaking, after DD came out with the cast valve covers and better gasketing, the oil was reduced nearly 100%. The biggest leaking cause was doe to the stamped valve covers and not being installed correctly, they wound up bent.
Happy New Year
Dave M
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« Reply #8 on: December 28, 2012, 05:43:40 AM »

I can assure you Dave I am old enough to remember the 12v71 lol and every part no rookie here @ 73 

good luck
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« Reply #9 on: December 28, 2012, 08:21:16 AM »

I owned several 12V's in trucks back in the day and at 80K lbs. they all got 4.3 mpg.  You are correct about the idle speed torque, when you let the clutch out you were going somewhere.  Clifford and I are well qualified for the grey beard class, lol.  During the mid 60's-'70's if you wanted big power your choices were 12V71, 1693 Cat, KT Cummins or Allis Chalmers for a limited time.
« Last Edit: December 28, 2012, 08:24:39 AM by Boomer » Logged

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TomC
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« Reply #10 on: December 28, 2012, 10:34:29 PM »

Now with the DD15 set at 475hp and 1650lb/ft torque running through the Detroit 12spd automated transmission with the new Freightliner Cascadia Evolution, from San Diego to North Carolina grossing 78,000lbs, keeping the cruise spd to 62mph and with all the aerodynamics that are available now on trucks-we got an average of 9.2mpg. Not bad for a smog truck that you can practically breath the exhaust. And it has more torque then any 12V-71NA every dreamed of. Even the 12V-71TTA was rated at 600hp with 1800lb/ft torque. If you want that kind of power now-the DD16 can be had with 600hp and 2050lb/ft torque.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #11 on: December 28, 2012, 11:17:07 PM »

Indeed, the current engine choices are vast.  The fuel mileage is a biggie and with the DEF the HP can go up big time.
Being on the edge of going over the hill, I have more memories of the older mechanical big dogs than experience with the computer engines.
My ISM500 @ 1550 ft lb is a total surprise, certainly not up to the 12V-71T, but close enought to be very acceptable, coupled to a Coach of 30,000 lb, it gets along very fine coupled with the Allison 4000R & a 3.94 rear.
I smile, it makes people wonder what's up.
Dave Mw
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chessie4905
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« Reply #12 on: December 29, 2012, 03:58:13 AM »

meh..just go with a 12v-92. Nothing sounds as good as a 2cycle Detroit

ATHS 08


detroit diesel 24v71 start up
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« Reply #13 on: December 29, 2012, 08:57:35 AM »

That is a 12V-71NA (Naturally Aspirated-no turbo) in the red truck. And the other is a 24V-71 that Detroit made for boats putting out 1,800hp @ 2,300rpm. That video has always irritated me in that the dingbat mechanic on the governor is just a nervous revving fool. Never do we get a really good rev and release out of it.

Just for information for some of you younger ones-the 12V-71 is a single block engine using 2 6-71 heads. The 12V-92 is essentially two 6V-92 blocks put together (although both the front and back block were specially made to be mated together) using 4 3cylinder heads. The 16V-71 or 92 was made the same way-two blocks, four heads.

In the larger 149 series they only made a 6V and 8V block. The cylinder combinations that were made from the factory were 6, 8, 12, 16 and 20.  How did you get 20? An 8V block in the middle with a 6V block bolted to the front and the rear. Needless to say was an unique sounding engine.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
wg4t50
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« Reply #14 on: December 29, 2012, 02:42:57 PM »

TomC, I agree, also no cooling on the last two videos,  makes me ill watching such idiots, sure not their money involved with that beautiful engine.
I also have a background with the 4, 6, 8, 12, 16 and 24 -71 series. most were in gensets or fire pumps including the 24 in gensets only. And lots of 82 series plus 2
6-110 gensets. stayed away of the 149 series, just the way we were setup.
Always felt you need to love them engines to do a proper long lasting rebuild,if it is just a job, you most likely will not have a long lasting unit.  seen too much of the latter.
MHO
Dave M
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