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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: NeoplanAN440 on April 07, 2010, 11:05:39 AM



Title: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: NeoplanAN440 on April 07, 2010, 11:05:39 AM
Anybody running a Cummins 8.3  (300HP Version) in their Bus ,or has done the swap????

My Bus and Trailer are weighting in around 40k-45k.Im running a 6V92 with HT748 right now,and look for more Hill climbing Power!

Will a MtT643 hold up,or should i use my HT748 behind it!!??

I was shopping around for a Big Cam 350 first,but the PT fuel system on these
makes running WVO a little tricky!!!!



Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: uncle ned on April 07, 2010, 12:04:23 PM


Why change engines when you can get 350 or more from your 6v92.

uncle ned


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: NeoplanAN440 on April 07, 2010, 02:29:59 PM
thats the answer i mostly get!!!

to be honest,im tired of chasing straight 40W oil,
im tired of watching my rpms and downschifting to keep boost up,
im tired of changing gaskets to work against detroits oil leaking reputation,
im tired (even that i drive on WVO) of getting 6-7 mpg,

i allready wasted enough money in injectors,turbo.
next step wpould be maybe blower gears,intercooler..........

for that amaount i can do the engine swap,and have low end power with no detroit worries!!



Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: luvrbus on April 07, 2010, 02:48:17 PM
What makes you think your going to gain more with a 300 hp 8.3 vs a 300 hp 6v92 ?

good luck


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Don Fairchild on April 07, 2010, 02:51:26 PM
the 8.3 won't do what you want, at 300 hp it only puts out 950 ft lbs tq. Go to an 8V92 or 60S, cat big Cummings.

and you still wont get much better mileage.

Don


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: luvrbus on April 07, 2010, 02:57:42 PM
 Don I thought a 300hp 8.3 was 860 ft# what ever they have it is weak lol


good luck


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Don Fairchild on April 07, 2010, 03:04:35 PM
Clifford, I agree, most of the 8.3's I have seen have either a rod hanging out the side of the block or the head came apart and tore up the block. Not a good engine to my thinking.

the electronic engine Tq is 950 @1300 rpm and the mechanical is 820 @1300

Don


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: DaveG on April 07, 2010, 03:07:56 PM
Hey, don't forget about changing gearsets too!


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Utahclaimjumper on April 07, 2010, 03:13:07 PM
In my opinion the transmission is equilly importand for all around performance. I run an 8.3 at 330 HP with the 3060 allison, the coach comes in at 39K with a 4400 Lbs. towed, allways does 9.5 to 10.8 on mileage. ( western US) Stays dry and uses no oil.>>>Dan


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: NeoplanAN440 on April 07, 2010, 03:14:33 PM
i prepare for my engine swap.
i was going pro and con between  a Cummins L10 or an 350 Big Cam!
im still researching how the PT fuel system will react on the more viscous WVO.

while searching for the engine and adapters and all the bits and pieces,i came along a
8.3 rated at 300hp,and was wondering how it will perform.
i know that these are a little overrated in most rv's,but i thought the 300hp mark is still
fine for these blocks!!



Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: BobBoyce on April 07, 2010, 07:54:45 PM
If you would really like to know how well the Cummins 8.3L holds up in transit service, just take a look at the transit agency surplus auctions. I keep an eye on a lot of these, looking for the occasional diamond in the rough. So many of the later model (mid-90's) 8.3L equipped transits are being sold with blown or damaged engines at nearly half of the typical mileage of the earlier model (late 80's) 6V92 equipped transits that are still running. Most of these agencies have very good maintenance schedules, but despite this the Cummins 8.3 just does not seem to hold up.

One such prime example is a fleet blend of this exact mix (1988 RTS w/6V92 and 1994 RTS w/8.3L) in the same transit authority, where most of the 8.3L are shot by 280K-350K miles, while the 6V92 have over 600K miles and are still running.

Bob


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: pvcces on April 07, 2010, 08:37:07 PM
Hi, Dan.

Which coach are you running that 8.3 in? That's pretty good mileage you're getting.

Thanks.

Tom Caffrey


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Lin on April 07, 2010, 09:44:38 PM
The other issue is the transmission.  An Allision 647, as I remember it, is rated at 900 ft/lbs and 305 hp.  The 643 may even be a drop less.  If you can stick with the 700 series, you will be much safer.


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: NeoplanAN440 on April 08, 2010, 07:19:30 AM
as said,i was asking because i could get a 8.3 for a fair price.but was wondering if its a little to small and overated.


i will be looking at another early L10 with a 9 speed roadranger behind it this weekend,thats still in the truck and can be testdriven.
from all my research,this is my favourite combo for now.
i allready wanted the roadranger behind my 6v92,but wasnt sure how it feels with the "sluggish" throttle of the detroit.

will have to decide if i keep the ht 748 behind the cummins,or if i will go with the manual tranny.






Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Utahclaimjumper on April 08, 2010, 07:44:48 AM
Hi  Tom, I bought an American Tradition 40 with all the whistles and bells,
I've put 10K miles on her so far and its great.>>>Dan  (My wife gets better mileage than I do with it)


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: TomC on April 08, 2010, 08:04:09 AM
8.3 is currently available up to 350hp and 1,000lb/ft torque.  The 8.9 liter ISL is the same block and available up to 450hp and 1300lb/ft torque for RV use-this would be my choice, and will be the engine I use IF I need to swap out my big Caterpillar 3406B because of smog laws.  Good Luck, TomC


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: mikelutestanski on April 08, 2010, 01:00:49 PM
Hello:   I average 7.4 with a mechanical 1989 L10 @300hp  with a B400R and 4.625 rear end.  THe double OD gears really help.   The roadranger behind an L10 will get another mile or so in my opinion.
   The computer engines do better mileage wise but can be more of a headache when they go south.  Not that they do that often and parts are hard on the wallet however the guy that is getting 10 or so has a sweet setup albeit driving habits do make or break mileage.   
    Any way good luck with your conversion/swap.  it can be challenging but a very worthwhile exercise especially when its running again..
   FWIW 
   Regards and happy bussin   mike


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: TomC on April 09, 2010, 07:46:02 AM
The mechanical L10 is a great engine for a bus.  It is compact enough yet robust for years of service.  And while it won't get the fuel mileage of an electronic engine, all you need is one electronic failure and all the fuel savings plus more go away.  Good Luck, TomC


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: luvrbus on April 09, 2010, 09:54:29 AM
I would go for a 3306DI Cat engine before the L10 Cummins far better engine been around since the 60's.DI stands for direct injection early 3306 engines had a pre combustion chamber.
good luck


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: NeoplanAN440 on April 09, 2010, 10:04:56 AM
I agree,the L10 is a nice engine!!

we just did the testdrive in the donor truck and im very happy with it.its hard to compare a empty tractor with my loaded bus,but it feels good so far.

now i have to decide if we take it one step up and even use the 9 speed manual or search for a ht 740 or b500??
i think it costs more to change the ecu settings on my ht748 to lower rpm and shiftpoints,then changing transmssions.
i have to admit,that i have a interested buyer in my engine tranny combo,and he wants the whole setup to make his swap easier!!! this would help me with the hidden costs that will show up while installing the new drivetrain.
also the transmission choice will give us the factor what rear end ratio we will use.

still lots of questions!



Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: TomC on April 09, 2010, 02:22:55 PM
I think you'll find that trying to add a manual shifter and a clutch pedal with linkage will be way too much work.  I wouldn't worry about changing the shift points on your HT748, since both the 8V-71 and L10 both operate up to 2100rpm.  Just make sure your linkage is adjusted correctly to take advantage of partial throttle shifts.  I know on my V730 on light acceleration, I can see early shifts where the engine rpm can come down to 1100rpm after the shift.  Good Luck, TomC


Title: Re: Cummins 8.3 Allison MT643 Performance What to expect???
Post by: Zeroclearance on April 09, 2010, 03:58:18 PM
Dan Holter has a complete Detroit S50 and B500..   Sell your powerplant and drop in a S50 and B500 that came from a transit coach.