Author Topic: Cummins 8.3 Allison MT643 Performance What to expect???  (Read 12700 times)

Offline NeoplanAN440

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Cummins 8.3 Allison MT643 Performance What to expect???
« 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!!!!


Offline uncle ned

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #1 on: April 07, 2010, 12:04:23 PM »


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

uncle ned
4104's forever
6v92 v730
Huggy Bear

Offline NeoplanAN440

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #2 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!!


Offline luvrbus

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #3 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
Life is short drink the good wine first

Offline Don Fairchild

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #4 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

Offline luvrbus

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #5 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
Life is short drink the good wine first

Offline Don Fairchild

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #6 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

Offline DaveG

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #7 on: April 07, 2010, 03:07:56 PM »
Hey, don't forget about changing gearsets too!

Offline Utahclaimjumper

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #8 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
Utclmjmpr 
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Cedar City, Ut.
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Offline NeoplanAN440

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #9 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!!


Offline BobBoyce

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #10 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
« Last Edit: April 07, 2010, 09:30:52 PM by BobBoyce »
1988 TMC RTS T70606 6V92TA DDEC-IV
Raleigh, NC - Capitol Area Transit #1205

1994 TMC RTS T70606 Series 50 DDEC-IV
Tallahassee, FL - FSU Campus Shuttle #9410

Offline pvcces

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #11 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
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska

Offline Lin

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #12 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.
You don't have to believe everything you think.

Offline NeoplanAN440

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #13 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.





Offline Utahclaimjumper

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Re: Cummins 8.3 Allison MT643 Performance What to expect???
« Reply #14 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)
« Last Edit: April 08, 2010, 08:58:31 AM by Utahclaimjumper »
Utclmjmpr 
 EX 4106 (presently SOB)
Cedar City, Ut.
 72 VW Baja towed