June 23, 2018, 06:42:10 AM

Author Topic: 8V92's  (Read 8968 times)

Offline Tin Lizzy

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« on: February 16, 2007, 04:04:06 PM »
Found a wrecker here in Alberta with an 8V92 Silver and an 8V92 TA. I am assuming the T stands for turbo. Will the 8V92 silver work for an MCI coach. ALso what transmission(Allison) matches up with these engines. I want to know as much as possible before I contact seller
Tin Lizzy
1972 MC 7
Calgary, Alberta

Offline Nick Badame Refrig/ACC

  • 1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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Re: 8V92's
« Reply #1 on: February 16, 2007, 04:37:19 PM »
Hi Harry,

I have a 8V92 silver in my 102C3.   I think more importantly, is the rotation of the engine. [right or left]

You will also find quite a few Allison trans will match to it. I have the HT740.

I'm sure you will get a few more replys here that may be more indepth then my reply.

Good Luck
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Offline TomC

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Re: 8V92's
« Reply #2 on: February 16, 2007, 04:51:56 PM »
The 8V-92TA (turbocharged/aftercooled) is an excellent choice to replace your 8V-71 since they are the same on the outside.  The 8V-92 has a vibration dampner behind the front pulley (looks like a small flywheel) that pushes the pulley out from the engine about an inch.  So your belt alignment would be off.  Compensating for that would mean to modify the engine mounts.  If changing to an automatic, you'll have to create new mounts for the transmission also.  If the engine is mechanically injected (has the throttle governor on the top left front of the engine) then you can use the HT740, HT748 (4spd, 4th gear direct), HT750, HT754CR (5spd, 5th gear direct).  You can also use electronic transmissions with a throttle position sensor that would be the HT741, HT 755cr.  Also the world 6 spd that would be the HD4060 close ratio, HD4560 wide ratio (not recommended, 1st to 2nd gear is a rough change), or the bus version B500 (same transmission just with a shallower oil pan for better ground clearance).  If the engine is electronic, then any of the above electronic transmissions will work.  The cheapest would be the HT740.  The best would be the world 6spd since the first four gears are essentially the same as the HT740 but with the addition of a .74 and .64 overdrive on the HD4060 and B500 or .76 and .67 on the HD4560.  If you go with the world transmission, there is nothing to say that you have to use both overdrives.  If your bus is geared tall, then the transmission just won't go into 6th, or of course you can just select 5th gear, or 4th, or..etc.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline busnut104

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Re: 8V92's
« Reply #3 on: February 17, 2007, 02:39:36 AM »
A coupl of other thing you will have to do is shorten the drive shaft 1" and install a 5" in and out muffler, a bigger air cleaner and bigger radiator and fans, the front motor mount is different, I installed a 8v92 in my mc8 and it is quite a job, I think if I would do it over again, I would have turbo. the 8v71. and there is more but I just named a few that came to mind, I made this change 4 or 5 years ago. But it sure is nice.

Offline TomC

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Re: 8V92's
« Reply #4 on: February 17, 2007, 06:32:47 AM »
Busnut104 makes a very important point.  It is much easier to pull your 8V-71, rebuild it to turbo specs, install an air to air intercooler, enlarge the radiators, air cleaner and muffler, than to change to the 8V-92.  Personally, I think (along with Don Fairchild) that the 71 series is a stronger engine.  You can run 90 injectors in a 8V-92 and get 450hp and 1350lb/ft of torque out of it.  Don is running 125's on his own personal engine, that would be pushing about 650hp.
My turbo project with a very mild increase from N65's to 7G75's, increased my power from 300hp and 800lb/ft to 375hp and 1125lb/ft torque.  That's more than most 6V-92's put out.  I highly recommend the turbo/ air to air intercooler way to go to get more power.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline akroyaleagle

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Re: 8V92's
« Reply #5 on: February 17, 2007, 08:15:31 AM »
Harry, The T is Turbo, the A is Aftercooled.
Check the serial number to be sure it is a Silver. If it doesn't have a blower bypass it will not make big HP.

If you are any where near Ponoka, (North of Red Deer, South of Edmonton) drop me an email (check in the profile) and I may be able to recommend the best Detroit 2 cycle mechanic I've ever met to help you. He did mine.

I also have quite a bit of the information and part numbers you will need.

Good Luck, Joe

Joe Laird
'78 Eagle
Sioux Falls, South Dakota

Offline muddog16

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Re: 8V92's
« Reply #6 on: February 17, 2007, 12:44:35 PM »
Here is a link that gives a complete breakdown of 8V92 identifications!


1982 Prevost LeMirage


Offline TomC

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Re: 8V92's
« Reply #7 on: February 17, 2007, 05:29:32 PM »
To correct, I meant you can run 90's in the 8V-71 to get 450hp.  If you ever saw the aftercooler on either a 8V or 6V, they are a joke-very small-like just enough so you can say you have them. Using air to air intercooler is much more effective-that's why vertually all medium and large trucks use air to air intercoolers now.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline LegalEagle82

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Re: 8V92's
« Reply #8 on: February 17, 2007, 07:53:41 PM »
I have an 8v71 (non turbo), and I assume stock size injectors, because I just have no idea.   Is it worth the trouble cost to upsize, and if so, what is the mileage difference.  Not that it could matter that much,  I seem to be getting about 6 mpg.   Tom are those hp numbers on the  TA models.    I'm all ears on this one, as I have no desire to change my engine out, but would love to get as much power as possible.  Thanks in advance

evan - LegalEagle

East Nashville, TN
Better described as living in the hood...
Legal Eagle
Nashvile, Tennessee
82 Model 10 8v71
95 Model 15 60 Series

Offline RJ

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Re: 8V92's
« Reply #9 on: February 17, 2007, 09:14:18 PM »
Evan -

Crawl into your bird's engine compartment and carefully pull a valve cover.  On the side of the injector you'll find a round tag with a letter/number on it.  Let us know what it says, as that will help us give you a more intelligent answer to your question.

However, as a rough guide, most coaches with an 8V71 in them came stock with N or C-60 injectors.  These give about 275 hp and around 770 ft/lbs of torque, and are really the largest injector you can use with the stock cam timing.

You can install 65s or larger, but unless you pull the engine and advance the cam timing, you'll just be blowing a bunch of black smoke, increasing the potential for overheating, and watching the fuel gauge drop more quickly.

How long has it been since you've weighed your coach in "ready-to-roll" condition?  Weight has an effect on fuel consumption and performance, perhaps a "diet" is called for?

Example:  My little 4106, which weighs in right now just a little over 20K lbs, will easily outrun the 500 hp 50,000lb Prevost Marathons up the 6% Grapevine between Fresno and Los Angeles.  Dead stock 8V71 engine w/ N60 injectors.  Weight DOES make a difference!  (The Marathon folk are NOT happy when I've blown past them, btw!  LOL)

One last thing to consider:

You will NEVER recoup the cost of a major HP increase over the life of your coach, from a strictly economic sense.  Visceral, yes, economic, no.  Your call. . .

FWIW & HTH. . .

RJ Long
PD4106-2784 No More
S13406 1978 MC-5C Converted
S14947 1980 MC-5C Shell
Cheney WA

Offline TomC

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Re: 8V92's
« Reply #10 on: February 18, 2007, 08:40:59 AM »
The 375hp with 1125lb/ft torque is what my 8V-71N turned into after turbo and air to air intercooler.  The difference- coming south from Las Vegas to Los Angeles on I-15, the big Baker pull used to be at 30mph pulling my car weighing 34,750lb total and after the big hill were a couple more times I had to down shift up other hills.  Now pull the hill at 40mph and once at the top, didn't see below any other hill and didn't ever down shift.  Now I feel confident to be able to go to Colorado and Alaska with the high altitudes and steep grades.  I'll probably have the bus for another 10 years, so it is worth it in my mind.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline MedicNovo

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Re: 8V92's
« Reply #11 on: February 19, 2007, 12:59:38 AM »
Does the engine have to be pulled to upgrade to do the turbo  modification? Also is the cost reasonable?
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Offline TomC

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Re: 8V92's
« Reply #12 on: February 19, 2007, 06:30:20 AM »
The engine does not have to be removed to turbo it.  But-it is a very good idea to at least pull one head and pop out one of the pistons to make sure it is two piece (iron crown with aluminum skirt) and that you have the tighter ring set to with stand the extra pressure of turboing.  Don Fairchild did that and luckily found that my pistons were both two piece and had the correct ring set.  Since my engine still has the high compression pistons (18.7 compared to 17:1), we kept the power boost down and only increased the injectors from 65 to 75.  IF you change out the pistons, you can go to 80 or 90's. It is always easier to pull the engine to do the turbo job.  That's what Don did with mine-course a transit V drive is different than a T drive MCI.  Good Luck, TomC
Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.

Offline H3Jim

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Re: 8V92's
« Reply #13 on: February 19, 2007, 07:15:43 PM »
Does Don Fairchild work on series 60's?  What is his number or email or web page?
Jim Stewart
El Cajon, Ca.  (San Diego area)

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Offline NJT5047

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Re: 8V92's
« Reply #14 on: February 19, 2007, 08:01:25 PM »
FWIW, an MC8 engine is very easy to remove.    Buy or build a dolly, or if you have a large fork lift that'll work, to pull the engine/trans unit.  All coolers and plumbing comes out with the engine/trans/cradle assembly.  A couple of decent mechanics can remove the whole unit in 4 hours. 
The dolly plans are included in an MCI service manual.  Pretty simple item.  That's the only special tool required.   If the quick disconnects are used on the PS lines, a 2.25" crows foot will remove them. 
I suppose a downside to the dolly is that the engine will have to be lifted off the dolly (set the cradle on a stand) to remove the oil pan.  This isn't a huge issue.  You wouldn't have to separate the engine from the trans or remove any coolers.   
If you had an MCI with an 8V92TA as a donor, the changeover wouldn't be too onerous...swap out the cradle with everything on it.  If you must piece the 8V92 powertrain together, I'd turbo the '71.  Be much less expensive, give good results if your engine is serviceable. 
Good luck with your project.  JR

JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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