Fuel economy 8V71 vs series 50

[Kevin Warnock]

Yes, there are lots of RTS busses out there that left the factory with Series 50 engines. They are starting to be sold off now by the transit districts. I got mine for $10K, in very good shape, with no rust, and under 400K total miles. This included the destination signs, new front tires and a wheelchair lift that worked perfectly. I spent $3,500 more to have the 4:11 gears installed, and $2,000 to have a 4 point leveling system installed. I take it in for painting tomorrow. The quote is $4K for two colors. Does that sound fair?

[kyle4501]

. . . .10-12 mpg with a manual?  Good Luck, TomC

Mine has the 8V71 (brown tag injectors) & 4 spd manual with 3.70:1 axle ratio. According to the previous owner, that is about what he got as long as he stayed out of the rockies. He kept a log that showed every expense. He put over 400,000 miles on it as a band tour bus.

So far, EVERYTHING he told me concerning this bus has proven true. He didn't drive like a maniac either, rather he had learned the 'sweet spot' & that's where he cruised.

I never said a s50 wouldn't work, just pointing out the biggest difference between the 4 & 6 cyl 4 strokes. If you accept this fact & include it in the design of the refit, problems can be minimized & future enjoyment will be maximized. (The shaking MUST be considered when planning a swap or you will experience premature hose failure where they connect to the engine. Also, there must be room for the engine to move.)

I know more than I want to concerning the counter rotating balance shafts used on engines . . . The short version is they only dampen some of the vibration, & it depends on a lot of variables to how effective they are. The fact that it will last 1,000,000 miles says a lot for the durability of the design.


Some people are more sensitive to vibration than others. I know the vibration of my 8V71 is almost nonexistant & since it runs fine w/ no smoke, I can't justify changing it any time soon. However, if I find a suitable donor drivetrain with an automatic & overdrive & jakes, all bets are off. 


By factory install, I was referring to a quality professional install vs a hack job by some monkey with a smoke wrench.

[cpschevy]

We have a case tractor we put a cummins N-14 in out of a truck with all the electronics from the truck. It has worked great untill about two weeks ago when it died , so i took the ECM into cummins and they told me it was dead! No big deal rite, think again they said they had a rebuilt one for only $2995.00!!  thats how much we paid for the whole motor used with all the electronics. So as others have said stick with the old mechanical motor much less to go wrong and cheaper to fix!!

[blue_goose]

Two cents from the person that did one. 
DD said in there info that the series 50 did viberate any more than the series 60.  They should know more than anyone else about that. 
It only takes 3 wires to make the DD ecm work.  If the ecm is bad or if you have a bad sensor it may not run.  These problems are few and far between.  If  you need a ecm for a DD you can get a 1V on ebay for $800.00 and get it programed for another $200.00.
Lets get this out of the way next.  Had my bus 21 years.  Started with fair 8-71, rebuilt it to new spec. in 1993.  Got about 6 miles to the gal.  Changed to 8-92 in 1998.  The 8-92 was a reman from DD that was set up for 350 HP.  Made a bad change by raiseing the HP to 475.  I could out smoke any one and only got 4.5 miles to the gallon.  There were no hills after that, if you could keep it cool enough.  That cool enough was a big problem.
Now I have a series 50 in the old bird.  Been in sence last November and I have only put a little over 3,000 miles on it so far.  Did the change over myself with help of 2 friends. Took about 250 hr of labor.  The next one won't take but about half the time.  Won't have to learn electronic engines again.  Lots of time spent reading and looking to make sure there were no mistakes. 
The engine that I put in came out of a city bus, that was monunted sideways.  The transmission reversed the direction.  I used all the parts that I could from the city bus.  Had to buy some air and oil lines, fan drive and lots of welding. 
There is no way that I would change back.  The bus runs the best that it ever has.  Not as much power as the 8-92, but getting twice the fuel milage.  That is two times as much.  Best cruse control that you could have and jake brake works better than any 2 cycle. 
I like mine so well that this winter I am going to take out a 6-92 in a 102A3 and replace it with another series 50. 
If I can help anyone that wants to make the change let me know.

[TomC]

Even though I just had my 8V-71 turboed and intercooled, and it puts out a respectable 375hp and 1125lb/ft torque, I am getting about 5.5mpg with it.  My 10240B AMGeneral transit was actually a Flyer D800.  These buses were made in one model or another, first by GMC called the classic, then MCI also called the classic ending in 1992.  Santa Monica bus lines has some MCI Classics running with the Series 50 and B500.  Seen the engine cradle, and it looks exactly the same.  When Santa Monica finally retires those buses, I'm going to buy one and just switch the cradle and rear end cradle along with the gas pedal and shifter.  Then will have close to a 10 mpg bus with a modern engine and transmission.  It is getting harder to find mechanics that are still familiar with the 2 strokers, and also finding the Delo 100 40 weight.  Good Luck, TomC