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Author Topic: 8V71 options  (Read 2632 times)
Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« on: August 13, 2009, 08:11:53 AM »

When people ordered MC-5s, MC-7s, MC-8s and MC-9s they had the option of ordering an 8V71. Did an 8V71 in an MC-9 for example, have different injectors and blower gearing versus an 8V71 in an MC-5? Bigger bus comes with more HP?

MY 8V71 in my MC-5 does just fine but I can't imagine pushing a bus that weighs maybe 10,000 pounds more with the same engine configuration? Add an automatic and A/C and I really can't imagine.

Fred
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Fred Thomson
bevans6
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« Reply #1 on: August 13, 2009, 08:17:48 AM »

I've wondered the same thing, and so far I've learned that they came with by and large the same 270hp bus type engine.  People may have hot-rodded them with injectors and injector timing after delivery, but most people talk about them being delivered with the same basic bus-tuned engine.

Makes me not worry quite so much about towing a 6k or 7k trailer...

Brian
1980 MC-5C with an 8V-71
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
luvrbus
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« Reply #2 on: August 13, 2009, 08:25:11 AM »

Guys even the 6v92TA engines in MCI's were 270 Hp and lower had something to do with the cooling on a MCI not a great cooling system.
I have saw 6v92 and 8v71 set at 244 hp in MCI 8's and 9's and the 8v92 set 304hp   

good luck
« Last Edit: August 13, 2009, 08:30:57 AM by luvrbus » Logged

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Airbag
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« Reply #3 on: August 13, 2009, 08:39:03 AM »

Guys even the 6v92TA engines in MCI's were 270 Hp and lower had something to do with the cooling on a MCI not a great cooling system.
I have saw 6v92 and 8v71 set at 244 hp in MCI 8's and 9's and the 8v92 set 304hp   

good luck

Can't be too bad they built thousands of the bloody things. I have zero cooling issues with mine even going up the steepest long grades in 100 degree days, never see more than 200 and my gen shares the same coolant. I know we don't have that massive gearbox and truck size driveshafts running the fan and AC compressor  Cheesy It's all in good fun you know. My favorite bus? The one I'm driving that day.
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luvrbus
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« Reply #4 on: August 13, 2009, 08:53:18 AM »

Sure they built thousands I owned a 5 and 8 and when you bump the HP up watch out they are going to get hot why do think they have so much aftermarket parts for the cooling.
It is not a normal system pushing water 2 ft above the engine to radiators to cool.
Glad you don't have cooling problems but most do   


good luck
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Lin
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« Reply #5 on: August 13, 2009, 09:43:38 AM »

I did not have any cooling problems on my MC5a, but I know that trying to get more power out of it is likely to start to cause a problem.  I am not sure though that having the radiators high up really adds anything to the problem.  Doesn't the siphon effect on the way down cancel the pump input on the way up?
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Airbag
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« Reply #6 on: August 13, 2009, 10:46:30 AM »

I really don't need more power or fuel burn. I have been around too many airplanes that have been upgraded with larger engines and what I have found is the factory engineers usually come up with the most harmonious power plant installations. I have often thought it would be nice to go up a hill a little easier but I'm Ok with what I have.
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Don Fairchild
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« Reply #7 on: August 13, 2009, 11:09:35 AM »

the 5's 7's and some of the 8's had the old low block or dry block and would not support more then around 275hp

Don
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Rick 74 MC-8
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« Reply #8 on: August 13, 2009, 01:51:29 PM »

 sorry
don't hit tab and enter
« Last Edit: August 13, 2009, 02:00:14 PM by Rick 74 MC-8 » Logged

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Rick 74 MC-8
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« Reply #9 on: August 13, 2009, 01:58:00 PM »

Don
     That's the first I heard of dry block how can you tell them from the late 871 I have a 1974 MC-8 . I know it has N-65 injectors and assume A timing witch is I think 318 hp I have never had a problem but 


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                                                            Rick 74 MC-8
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luvrbus
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« Reply #10 on: August 13, 2009, 02:12:49 PM »

Not Don but Rick they are easy to tell the difference in the two the old style dry block has large oval shaped air box inspection covers with a bolt in the center.
The later 8v71 has oblong covers ruffly 2in w x 4 inches long with 2 bolts below the heads.
It should be in the archives I remember Cole trying to explain the difference to Gus in one of the famous antifreeze debates here.    

good luck
« Last Edit: August 13, 2009, 02:15:45 PM by luvrbus » Logged

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Fredward
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MC-5A #5401 8" roof raise 8V71 with MT647




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« Reply #11 on: August 13, 2009, 08:35:44 PM »

So based on what I've read so far, if my buddy buys the MC-8 with 871 auto, I'll be able to keep up with him on the Interstate with my MC-5 8V71 N65 with 4 speed Spicer.
Fred
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Fred Thomson
Ed Hackenbruch
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« Reply #12 on: August 14, 2009, 06:58:46 AM »

So Clifford, any idea as to what year they changed from the old style to the newer?
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
bevans6
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« Reply #13 on: August 14, 2009, 07:11:44 AM »

your buddy has an 8V71 auto in an MC-8 and you have an 8V-71 Spicer in an MC-5, you should be able to have the coffee made by the time he catches up with you at the lunch stop!   Grin  Unless you have transit gearing and a top speed of 50 mph, of course... Shocked

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
bevans6
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1980 MCI MC-5C




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« Reply #14 on: August 14, 2009, 07:18:05 AM »

On the cooling thing with the rads up top, water pumps like to push, they don't pull very well.  So having a decent head of pressure to force the water down into the engine is a better thing than making the water pump push the water back uphill again.  yeah, it does consume some of the energy imparted to the waterflow by the pump, but that is reducible by correct water pump sizing.  Secondly, the head pressure of water in the engine creates a natural reluctance to cavitate, so cooling is naturally maybe not improved, but at least presented optimum conditions.  Finally, one of the big bug-bears of designing cooling systems is creating an automatic air bleeding capability.  you need to naturally allow air to flow upwards out of the nooks and crannies in the block, etc.  Having a big header tank up high is a great way to get started on that, as is having the rads up high.  So I think, on balance, having the rads up high is probably not optimum, but not the worst thing either. 

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
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