changing engines 8V71 to a 8V92

[DavidCA]

I have  1970 MCI 7.  I am considering replacing my 8V71 with a 8V92 but am worried about overheating.  I live on the central coast of CA.

I am looking for more power to climb hills a little faster.  My 8V71 has 250,000 miles on it and is overheating.  I have a 5-speed Allison transmission.

Wondering if anyone has done a similar project and would appreciate any good or bad experiences.  Looking for a recommendation of a shop in CA that could do the labor as well as suggestions on where to start shopping for the engine.

Thanks,

DavidCA

This was my first post.  All of you who responded, I appreciate your suggestions & help.  I will check into them further but thanks for sending me in the right direction. 

[TomC]

You will double the power going from a 8V-71 to a 8V-92TA. You will also double the cooling need. Why not turbo your 8V-71? N60 injectors on the 8V-71 will give you 280hp and 740lb/ft torque. N65 injectors will give you 304hp and 800lb/ft torque. I turbo'd and installed an air to air intercooler using 7G75 injectors that give me 375hp and 1125lb/ft torque. 8V-92TA will give you 450hp and 1400lb/ft torque.
Might consider installing a Detroit Series 50. Greyhound converted some 8's or 9's. So efficient, they eliminated one one of the radiators and used the other radiator space for the air to air intercooler. Series 50 can put out 350hp and 1150lb/ft torque-more than enough. And you can get 10mpg! Good Luck, TomC

[Scott & Heather]

Having owned coaches with both the 6v92TA and the 8v92TA, I can tell you I never fought heat issues with the 6v92 but I constantly have to keep a vigil on heat buildup on my 8v92. It's set to a 500hp program and it's quick. I can beat most any truck heading through the mountains on the way up (heading back down is a different story), and it has amazing power, but it does build up heat fast. I have two of the largest 8 tube radiators you could get in an mci at the time, my rear engine doors are removed, my radiators and cooling box are all rebuilt, and I have a small pulley on my cooling fans and I still can overheat. If I were transplanting an engine, it would definitely be a 4 stroke.


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[bevans6]

The good news is it's an easy swap, as these things go.  There's bad news - the MCI engine configuration is a little different than most with respect to engine mounts and such, and you may need to do a lot to your donor engine to get it to fit on the cradle correctly, swap out or completely re-do the accessories on the rear drives (compressor, power steering pump, alternator) and that may require opening the back of the engine and changing or installing drives.  Heat will be an issue, since horsepower equals heat in a two stroke.  Your cooling system was designed for around 280 hp, so adding a lot will be an issue.  I have a turbo 8V-71 with around 350 hp in my MC-5c and it doesn't over heat, but you can tell it's at full capacity.  You can set an 8V-92 for 350 hp and it will be easier to cool.  There is room for a S50 in your MC-7, and that was a popular conversion for a while.  The S50 gets around 350 hp with the right software, and is very easy to cool.  It is definitely possible to add the cooling for a big HP 8V-92, just add that to the list of stuff you need to do for the swap.

Brian

[blue_goose]

Don't do it, if you can't keep the 71 cool you will never be able to cool the 92.  Cooling system in MCI 7 not anywhere large enough for 92.
Jack

[kyle4501]

For the cost of the change, you could get a newer coach - even a high end factory built unit.

So, while you are getting prices for the engine upgrade (be sure to allow for unanticipated expenses) --- look at the used coach adds to see what else is out there.

The above posters went with a repower.

I abandoned my conversion project in favor of a factory built unit.

Good luck with whatever you do.

[Boomer]

Reman 8V92 + new radiators + new muffler & air cleaner + fab work + labor by pro shop = 20K to 30K.  Is your bus worth it?  You decide.  JMO

[buswarrior]

MC7 cooling system was never intended to have an automatic transmission to also keep cool.

Every model change, MCI enlarged the rads and was constantly playing a rear guard action through the 7-8-9-102A-B-C-D.

Are you getting everything from your current set-up?

Cooling system flush with proper 2 part chemicals?

Get a full size Hayden cooler to take care of the transmission, to eliminate that heat load.

Button up the fan compartment properly so that ALL the air is sucking through those little radiators, not around, or though holes, or through the door seals.

No reason you shouldn't be able to run that coach flat out with what it's got up the mountain, with modest remediation.

And none of this goes to waste, all good preparation to turbo charge what you have, or prepare to carve bigger holes for bigger radiators.

happy coaching!
buswarrior

[luvrbus]

You didn't mention which model of MCI 7 you owned, the MCI 7 combo with the 1 single radiator has no heating problems with a 8v82

[kyle4501]

You didn't mention which model of MCI 7 you owned, the MCI 7 combo with the 1 single radiator has no heating problems with a 8v82

They used a Scenicruiser drive train to make the combos. Definitely plenty of room for a HUGE radiator.

[Emcemv]

I'm the one with the MC7 combo that has the big side radiator. Ours was converted to a 8V92T 450HP and Allison 740 in 2000 and it is still going strong.  Can't comment too much on overheating, never had any issues but we have not really tested it out west in the summer. I can tell you that we love how it drives, the power is nice. We are getting 6MPG.  Good luck with your decision!

[kyle4501]

6mpg - - - - you are doing good! 

I don't expect anything over 5, so I am thrilled when mine gets 6. 

[luvrbus]

Sierra Mining had a MCI 7 combo with 12v71 and a Allison 70 from the factory,I have seen several MCI 7's with factory installed Allison 70 transmissions (wet torque converters and 6 speeds) 

[uncle ned]

Kyle   HUGGY just got a little over 7mpg on a 730 mile round trip to Charleston sc.

Filled up at the hot spot in Chesnee SC coming from Palmetto cove Home.

Filled back up coming back from Charleston.  Used 96 gallons.

That is the scenic route and never over 60 mph.  2 days going and 2 days coming back.

Took grandson to a 2 day experience at the Citadel.  He thinks that is where he wants to go.

uncle ned

[kyle4501]

Ned,
I am looking forward to being able to take the scenic route & the time to enjoy the trip as much as the destination.

As for now, I must use the interstates if I am to go any distance.