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Author Topic: Repower MC9 Conversion from 8V71  (Read 14716 times)
arl
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« on: October 24, 2010, 06:27:49 PM »

[NOTE:  This is a parallel post to something I put on another bus site.  If that's not kosher, please let me know.  I'm really just trying to get this problem solved, not trying to be a pain.  Thanks!]

Howdy everyone. I'm quite sure you've answered this question many times, but my searches through the archives aren't getting my the answers I'm looking for. If you know of an exhaustive post already done, please point me to it. If you have ideas, please let me know.

I am desperately seeking a solution to the repowering of my existing 8V71 and Fuller 5spd manual to something else. ANything else. I hate that engine. It's loud and sucks fuel and pukes oil. It has no turbo, the tranny has no overdrive. It's killing me one mile at a time and I want to upgrade. It's burned four valves in two years, uses a gallon of oil every 400 miles, and just badly needs an overhaul (which the previous owner said it already had). I'd rather spend the money on some improvements.

SO... what's the optimal engine/tranny combo for repowering an MCI-9 with 8V71? I'm a guy that just wants to get me and my family from point A to point B reliably and as efficiently as possible. I don't need extra horsepower, I don't need fancy anything - well... cruise and jakes would be nice if easily incorporated. I'd like the engine to have turbo and the tranny to be either autoshift or automatic, though this is not essential as me and my kids have learned on this Eaton Fuller 5spd and are comfortable with manual.

Also, where are salvage sources for these powerplants?  Wrecked trucks, fleet sales, etc.?  Any help is greatly appreciated.
Many many many thanks in advance for your expert and thoughtful help getting me back in service.
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robertglines1
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« Reply #1 on: October 24, 2010, 07:17:43 PM »

Boy you sure picked a highly debated topic..The 8 v 71 is a dependable work horse..if your happy with the level of performance repair it..if you go to a 8v92 you will need to change radiators and loose fuel mileage will be up to 20% less.  Automatic swap is nice addition,but will also cost fuel..6v92 is a poplar swap with a automatic but hp increase is minor.  Others will comment for sure. As far as I'm concerned it's your decision..How much of the work can you do yourself? in frame? prob not a complete rebuild  before -lots of sellers say recently rebuilt..and they might of only rolled bearings in it or less. In my Mci 8 with a 8v71 automatic I got 6.8 mpg..should do a little better with the standard.
« Last Edit: October 24, 2010, 07:22:11 PM by robertglines1 » Logged

Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
robertglines1
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« Reply #2 on: October 24, 2010, 07:28:00 PM »

where it says search up to the right  put in Engine swap..several links to what others have done  one was a 8v71 to 6v92 swap
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
Brian Diehl
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« Reply #3 on: October 24, 2010, 07:46:40 PM »

Or my way ...

http://home.earthlink.net/~diehls0792_1/BusSection10.html

Let me know if you want more pictures or information as I'd be happy to chat about it.
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luvrbus
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« Reply #4 on: October 24, 2010, 07:58:32 PM »

I was at Quartzsite last week and a guy had a trailer load of different Cummins engines for the 300 hp L10 he was asking 500 a pop,the L10E with the ECM were 800, M11 were 1000,1250 for the electronic version and ISM with the ECM for 2 grand not bad prices but no way of knowing what you would be buying.
Melbo has a L10 and ZF auto in his MCI and he likes it


good luck
« Last Edit: October 24, 2010, 08:02:39 PM by luvrbus » Logged

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arl
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« Reply #5 on: October 24, 2010, 08:15:37 PM »

Goodness Brian,  I don't think I can wait that long or spend that much time on a swap.  It needs to be finished by mid January next year.  I like the ISM, and the mileage you're getting, but I don't like the idea of cutting the floor.
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rv_safetyman
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« Reply #6 on: October 24, 2010, 08:18:16 PM »

Arl, cross posting is OK, but then you don't get as good of a dialogue as people respond to the thread.

Brian's conversion is an excellent example of what can be done.  My project pages (in signature) has some details on my conversion in an Eagle.  The process has many similar construction processes between various coaches.

As has been said, the subject is extremely broad and complex.  I wrote a three part series on engine conversion in Bus Conversion magazine.  It was not a how to do, but rather, all of the things you need to consider and all the options that exist.

Not sure how you searched, but the topic has been covered in many threads over the years.

Part of your study must address who will do the conversion.  If you think about doing it yourself, you will need a ton of skills and equipment.  If you have someone else do it, plan on at least $10K in labor for a cheap shop and up to $30-40K for an experienced shop.  Many shops will tell you they can do the job since the stuffed a Chevy in a Jeep, but that is not even close experience.

If you think about going to a four stroke, then gearing will be a big issue.  Buying the engine is a gamble (I lost) and can create a great deal of heartache and mental anguish (and added $$$$).

Some folks have added a turbo to the 8V71 and are happy with the modification.  Sounds like you can balance a conversion against a rebuild cost.  However, the rebuild will always be less expensive.

Just some random thoughts.

Jim
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Jim Shepherd
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85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
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Melbo
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« Reply #7 on: October 24, 2010, 08:22:22 PM »

I have had an excellent time with the L10 cummins -- I may not be as enthusiastic about the ZF -- not because it isn't a good transmission but because it is not well supported in the US -- the more places you can get service the better off you are and the L10 can be serviced anywhere as can many transmissions.

Also the engine runs up to speed and cool on temps -- Mike had his fuel pump rebuilt and got a bump up in HP

I have about 20K miles on my repower

L10s are easy to find -- to use a jake will take a little mod for the height of the engine

I would be glad to provide more information if you want

HTH

YMMV

Melbo
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If it won't go FORCE it ---- if it breaks it needed to be replaced anyway
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« Reply #8 on: October 24, 2010, 08:24:29 PM »

arl, you answered your own question.  There is no way to do an engine conversion in the time frame you have.  Brian's conversion is typical of the very involved process.

Given that you will not be able to do a conversion, you need to see if you can get your engine performance improved.  First, with all the oil, I have to wonder what oil you are using.  You must use straight 40WT oil specified by DD.  Next, you need to find someone who can run the rack for you.  

Then learn to live with it for a while until you can gather all the information you need to make a very complex decision.

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
cody
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« Reply #9 on: October 24, 2010, 09:01:07 PM »

Just as a random thought, these buses have run countless miles with various engine/tranny combinations, none of them are racecars but all were at some point well thought out for the most part and good running combinations, if one isn't measureing up to a persons expectations I'd check the possible combinations of fixes available before replacing the engine and possibly opening a major can of worms, sometimes just the proper oil will make a world of difference, straight 40wt cf2, tho many will say 15/40 is fine, it isn't, another heart breaker can be an out of adjustment on the rack, make the best of engines run like a ruptured duck in a bean pool, lots of possible fixes that'll give new life to what appears to be a hopeless case sometimes.
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robertglines1
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« Reply #10 on: October 25, 2010, 04:30:34 AM »

you  said  a gallon every 400 mile..The question I have is it burning it? is it leaking it?  Do you have smoke?  what color?   You ask for source for engine -just post here//.need one on one help? tell us what part of country your in.   Bob in SW Indiana.
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bevans6
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« Reply #11 on: October 25, 2010, 04:50:56 AM »

In your position, there is only one thing I would do.  I would find and buy a complete power package from another MC-9.  That would be transmission, engine, radiators and all.  I would probably look for the more common 6V92/Allison 740.  I would buy the best set I could find, slot it in there, and pray that not rebuilding turns out to be a good idea...

I would not look for an overdrive transmission unless I was changing to a four stroke engine.  The two strokes have to run at their designed rpm range in order to work properly.  That's just the way they are...

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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5B Steve
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« Reply #12 on: October 25, 2010, 06:02:26 AM »



   You might check some post that Tom C has explained on his re-powered 8V-71 to the TURBO version.  Some real good articles.

    Steve 5B........
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kyle4501
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« Reply #13 on: October 25, 2010, 09:29:58 AM »

You talk of horrible fuel mileage. What is your fuel mileage? Your driving style will have a huge impact on that. If you run 55mph, you will get better than if trying to run 70mph.

Having your current engine properly inspected by a good 2 stroke mechanic & tuned (if inspection indicates it needs it) will be a wise investment.
The wrong oil will cause excessive oil consumption - especially in an older motor.

Another thing, you can ruin a perfectly good 2 strokes by driving it like a 4 stroke. You must get the rpm's up. If you're pulling a hill & you can't accelerate, you're in danger of hurting the motor - watch the water temp, the 2 stroke won't survive above 200F.
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arl
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« Reply #14 on: October 25, 2010, 09:41:58 AM »

To Everyone, a hearty thank you for your time and attention.  You could be doing other things and I appreciate your willingness to share your wisdom with me.

I hear the points about balancing the cost of repower (time, aggravation, expense) with the cost of rebuild.  I can probably get a rebuild done for under $3K as my diesel expert also mentors my boys and they do most of the work under his supervision.  If you ever need work done in/around southern KY, call Ronald or Kerry Matney at Matney Diesel 270-932-7889.  They're amazing people.

I just don't like the 2-strokes in general.  I know that probably hurts some feelings, but I don't.  Loud, smelly, messy.  I don't like my tranny either.  Manual 5spd, raking all the time, clutch is annoying and generally useless.  The whole thing is annoying.  But that's not reason enough to spend countless hours and God-only-knows-how-much money making it different.  Unless the repower can be done reasonably and timely - and make a huge difference in the end.  That post from Brian Diehl on his repower to an ISM was enlightening - but he's apparently much happier now.  I like the idea of better mpg.  9 mpg or better will pay back over time as I currently get 6.2 on average.  We drive about 20-30K miles per year.

My coach is set up wonderfully so I'm reticent to just get a different unit.  But that's an option too I guess.

Bottom line is I need to get to the place where my bus is working for me, not the other way around - however that works.

I'm in Southern Central KY, near Greensburg, if that matters.

Thanks so much everyone!  Keep the wisdom coming and I'll put it to use - I promise!  In fact, I'm going to write up a more exhaustive description of our situation and see if that doesn't help drill down to a clearer answer.  I'll post it soon.

Alan
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