I have decided to start the search for a series 50 for a repower

[Tom Y]

Rick, The 25-40 would be for having it done. I do agree its not worth the money for MPG. But I can start my bus in the garage with out filling it full of smoke, I like the 4 strokes. I can ajust the idle up and down, I have cruise, cooling problems,there are other advantages. So each to there own. Tom Y

[Lin]

There was someone I spoke to in Oregon.  I forgot his name, but I got is from Nimco.  He said he had repowered his MCI with a Cummins and ZF.  He said he could do mine for around 15k.  My interest, which recurs periodically is about going for an auto trans.   I am going to use my 8v71 until it bales on me, but for those that have money the needs to be spent, options are available.

[skipn]

And it is basically a bolt in (no real structural mods)

FWIW

Skip

[Kevin Warnock]

My Series 50 in my 1994 RTS is getting me 10.75 mpg. I was thrilled with it until I read this thread. I thought I was going to be able to get parts for it for decades from now, like people can still get parts for 8V-71s decades after they were in wide use. Is that not the case? Will I perhaps have to buy a whole bus or truck down the road just to get the engine parts I need? My engine only has 370K, and it has a brand new computer according to my mechanic who inspected the bus before I purchased it. I was under the impression I could drive this engine for the rest of my life since it's a so-called million mile engine. I put few miles on it, so it would take me decades to put even a couple hundred thousand miles on it. If I have to change engines, what are my options. I have the 731R transmission and 4:11 gears.

Thanks,

Kevin

[Lin]

Kevin,
    Although there is a value to knowing your options, it is possible considering the kind of service your engine is doing, that it will outlive your interest in the bus. 

[NJT 5573]

I passed on a running truck with the 50 engine and a 10 speed with 160,000 miles on it at Christmas. You would get ALL the parts and this one sold for $7300. Retired from Home Depot. 10 speed.

My 92 is real low miles and I really can't justify a swap right now. If I have to, I have a spare 92 and a mechanical Cummins on the shelf along with a 10 speed double OD as well as a 13 speed.

Try to buy a whole truck, it will save a lot of money and give you options you will end up paying for anyway. Things like throttle potentiometer, after cooler, hoses, DDEC harness and even the standard transmission if you really want to get some fuel mpg.

[TomC]

Even at $5.00/gallon- if you're getting 6mpg now, and if you changed to an electronic 4 stroke that got 10mpg, it will still take around 100,000miles to recoup the difference.  I'd say most of us will never put on that kind of mileage over the life of the bus.  Good Luck, TomC

[RickB]

I will do around 25,000 miles this year alone and this has been a light year. If diesel ever becomes more reasonable (all you political types please resist the urge to turn this into a non-bus related never ending vamp) I will probably return to my 35-40k a year. I have less than 40k on my 8v71 but it is already showing signs of either a cracked oil ring or bad blower seals. I don't know who gets the "worry free million mile two strokes" that everyone claims are out there but I certainly have been passed ove a number of times by the Detroit Diesel two stroke fairy. I have been told by numerous DD techs that 250k is the best scenario imaginable for a dd two stroke and that to accomplish that you will average 5-10k in maintenance to get there. I am going to take the previous posters advice to look into a turbo with a lower boost setting to see if I can limp this old girl just a litlle more efficiently.
I know I make it sound like she doesn't run well, but in truth my bus runs like a top and other than running her out of fuel after filling the tanks at a fuel stop ( man you guys are thinking what in the heck is he talking about aren't you? The line was already pulling air befote I stopped. ) I had a full tank and I was out of fuel. Not a particularly good way to part with $350 to get her running again, she has run perfectly and has never missed a beat. I just wanted to give that 8V some well deserved kudos I guess. As usual you guys never cease to amaze me with your know;edge and D-I-Y spirit. Too bad most of you didn't help design these things.  RB

[Busted Knuckle]

I will do around 25,000 miles this year alone and this has been a light year. If diesel ever becomes more reasonable (all you political types please resist the urge to turn this into a non-bus related never ending vamp) I will probably return to my 35-40k a year. I have less than 40k on my 8v71 but it is already showing signs of either a cracked oil ring or bad blower seals. I don't know who gets the "worry free million mile two strokes" that everyone claims are out there but I certainly have been passed ove a number of times by the Detroit Diesel two stroke fairy. I have been told by numerous DD techs that 250k is the best scenario imaginable for a dd two stroke and that to accomplish that you will average 5-10k in maintenance to get there. I am going to take the previous posters advice to look into a turbo with a lower boost setting to see if I can limp this old girl just a litlle more efficiently.
I know I make it sound like she doesn't run well, but in truth my bus runs like a top and other than running her out of fuel after filling the tanks at a fuel stop ( man you guys are thinking what in the heck is he talking about aren't you? The line was already pulling air befote I stopped. ) I had a full tank and I was out of fuel. Not a particularly good way to part with $350 to get her running again, she has run perfectly and has never missed a beat. I just wanted to give that 8V some well deserved kudos I guess. As usual you guys never cease to amaze me with your know;edge and D-I-Y spirit. Too bad most of you didn't help design these things.  RB

RB,
Been there done that! Got the nasty smell of diesel fuel all over me to prove it! LOL! And if I'd been around back then they probably still wouldn't have let me help design them. But I'd been fooling around with ways to "improve" them from the get go!   BK 

[blue_goose]

I know it isn't good for me to answer what I have read here.  Lots of things that I have seen in my long life were more fiction than fact.  Most from people that had just heard something and taken it for fact.  I can remember hearing lots of bad things about airplanes from people that had never flown one of that type.  The same with cars some like a ford and some like Chevrolet.  Some of the things that have been said here about the DD 50 is nothing but hear say.  There is not a problem getting parts, there are no problems with getting service.
I have had my bus for 22 years; so far it has had a 8v71, 8v92 and series 50 engine.  I have probably driven motor homes and buses further than most of the people on this net.   In the last 30 days I have driven a motor home 7,000 miles, 6000 miles in a 2008 Monaco with a 650 hp Cummings the other 1300 in an American Eagle with a 400 Cummings.  I have driven my own bus 192,000 miles in the last 22 years.  The only reason for this information is to let you know I have been doing this for a while now.  Doesn't mean I know any more because of that.
Let's get back to the series 50; the engine is just the same as a series 60 except for the balance shaft.  True they are not going to make any more series 50 because they didn't have enough sales for that engine to do the engineering for the pollution control that would be needed. (This was info from Detroit)  May or may not be so (hear say).  The engine had the same guarantee as the series 60.  There is a factory rebuilt in the showroom now at Detroit of Orlando.  Unless it has been sold since I was there.  This engine just came in about a month ago.  It has a ecm4 and no other assorys.  You can buy it for $15,000 exchange.  I fell if you call any Detroit dealer they will be glad to sell you one for this price.
I have seen lots of series 50 engines and have never seen one with a bad block.  I am sure there are some that are bad.  I am also sure you will find the same in Cummings and Cat.
This isn't the easiest engine to put in some of the coaches.  Jerry wasn't correct when he said you didn't have to raise the bed in an Eagle to put in the series 50.  He just didn't remember that I had already done that when I put the 8v92 in with the turbo on the top.  Glad that was already done. 
The most important thing I am trying to say here is that in the modern engines there are no real bad ones. Again there are Fords and Chevrolets some like one and some like another.  Some of the prices for changing the engine here I think are high.  If you were able to build the coach and can do the welding yourself the change can be done for much less.  If you use the same transmission that you have now the change other than the price you pay for the engine shouldn't be any more than $4,000.  This will include $1,500 for a rear end.  If you buy a world transmission add another $5,000 to $10.000 to the price.
I have only put the engine in one Eagle and two MCI buses.  The MCI is much easer than the Eagle.  There are NO changes to be made in the MCI frame to install the series 50.  Just lots of pluming, most of the work is in the air to air and the cooling system.   You do have to change the cradle for the engine.  I do have the proper info for the changes if you need them.
What difference dose it make if you are putting a engine in the bus that is no longer being made.  Most of our busses haven't been made in past 20 years. The two cycle engines are no longer made for our use.  There are no engines being made now that are not electronic.       There are lots of good late model electronic engines out there for less than you can rebuild your old two cycle.  Fuel is never going to come back down like we would like to see it.  There are lots of people looking for good two cycle engines for the bus service.  If you have a good one you can always sell it to recover some of the charge for the change.
One last thing before I stop.  I won't call any names, but one of the most knowledgeable bus people in the southeast just finished his conversion.  He went from a 8v71 turbo with a 10 speed to the series 50 with a 10 speed.  He is now on his first trip with the series 50.  His overall MPG for over 100,000 has been 5.8 MPG. First leg of his trip all through the mountains was 7.2 MPG.
Jack

[makemineatwostroke]

Jack, if you would like to see bad blocks on some series 50 just stop by any of our locations (Stewart and Stevenson) across the US The bad blocks are more common on the LNG engine but it happens to the diesels also but don't let anyone tell you parts are going to be easy to get, that engine has been out of production since 2004 and the more they destroy the fewer parts need to be furnished for a couple of more years and fwiw we can not buy a new 50 series and we are one of the largest dealers in the world for DD another bit of info for you can not use a Mexican rebuilt engine for warranty work it has to be new if replacing the engine

[blue_goose]

I am sure that you can't buy a new series 50.  Don't think anyone in this group would want to do that.  What I was trying to say is you can buy a takeout engine for less than a rebuild and have a modern engine that doesn't leak and get better fuel MPG. I don't think anyone will ware one of the takeouts out.  After 22 years I still haven't put 200,000 on my bus.  There are lots of other things that I like about the new engines, cruse control, fast idle that you can control, lots of torque, no heat problems, if you do have a brake down on the road you can have it worked on anywhere (almost). By the way I spent about 6 hr at one of Stewart & Stevenson places in Wichita Falls, Texas last mo. having wheel bearings put in a new coach.  Nice people there.
Jack

[makemineatwostroke]

Jack, I like the new engines too I just replaced my 8v92 DDEC with a B500 Allison  with a 600 hp series 60 but I used the CAT CX35 8 speed automatic nice transmission.I pulled every string I could to get the new DD15 but it wasn't enough even working for the people.fwiw the series 60 fit a model 15 Eagle easy with no floor raise.enjoy your series 50 it's just not my favorite engine

[JohnEd]

Jack,

Nice post and thank you.  I thought everybody else had some good points, as well.

John

[TomC]

Unknown to most, the off road division of Detroit Diesel/MTU still makes a select few 2 strokers for military vehicles that are designed around these engines.  The models I know are still being made are the 6V-53TI, 6V-92TA, 8V-92TA, 12V-71TA (might be more).  Just like Cummins is still making the VTA903 for the Bradley tank at 800hp and 1425lb/ft torque.  But-Detroit is NOT making anything for the Series 50 anymore.  Good Luck, TomC