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Author Topic: 8v71 power  (Read 3629 times)
Cary and Don
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« on: February 28, 2011, 09:09:17 AM »

How much of a difference in power would we notice between a 4107 with a 6v92ta and an eagle with a 8v71?  We are used to rolling right up hill.  Will the Eagle go uphill too, or are we looking to 35mph?

Don and Cary
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luvrbus
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« Reply #1 on: February 28, 2011, 09:40:06 AM »

You not going to fly up a hill with a 8v71 in a converted Eagle weighing over 30,000 lbs just not enough there you are looking at 277 hp stock - 40+ hp for the fan- 25 for the stock alternator- the power steering not much left ok 

good luck
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gus
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« Reply #2 on: February 28, 2011, 11:42:56 AM »

My 4107 probably weighs around 26,000 lbs with a 8V71 and it is no hill burner so an even heavier Eagle is bound to be slower unless you have more than four speeds.

The 8V71 also comes in two different HP versions, 280 and 318. The 6V92 without the TA is 276.
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Cary and Don
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« Reply #3 on: February 28, 2011, 12:12:00 PM »

Do they ever put on turbos without blowers? 

Don and Cary
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lostagain
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« Reply #4 on: February 28, 2011, 12:18:17 PM »

The blower is needed on a 2 stroke to provide air intake pressure for starting and iddling.That air press. is needed for the scavenging stroke. Once revved up, the turbo provides the boost. Some DD 2 strokes have a blower bypass that opens to let all the air press. from the turbo to go straight to the cylinders.

JC
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JC
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Cary and Don
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« Reply #5 on: February 28, 2011, 12:24:54 PM »

So to add the turbo to a 8v71 would basically be adding the turbo to the existing blower and reroute the exhaust through the turbo?  I have heard mixed information on the 8v71 being able to withstand the extra pressure of the turbo.  Can the pistons and rods survive the turbo?

Don and Cary
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lostagain
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« Reply #6 on: February 28, 2011, 12:31:49 PM »

To turbo an 8V71 properlly, you have to have cross head, 2 piece pistons and the rods to match, later model valves to withstand more heat, later model blower seals to withstand the extra boost, possibly more suited injectors, etc. But the resulting increase in power and torque, and lack of smoke and sustained power at altitude is worthwhile. I did that to my 4-71 in the Courier 96 with great results.

JC
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JC
Invermere, BC
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« Reply #7 on: March 01, 2011, 11:41:35 PM »

Jc,

What do think the investment would be in $$  ?

I may be purchasing a 1970 Gmc 4905 with the 8V71 and wondered if a Turbo would be cost restrictive or impractical. 

Would the tranny need some beefing up?
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« Reply #8 on: March 02, 2011, 05:44:38 AM »

I recall approximately $5000. Pistons, rings, liners, rods, bearings, gasket kit, seals, rebuilt blower, turbo, rebuilt head, injectors, intake and exhaust plumbing, etc. And this was for a 4-71. I did the labor myself. Remember you will need more intake air volume, and make sure your exhaust is big enough, and it will put out more heat, so you might have to look at your rads, rad blowers...


JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
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« Reply #9 on: March 02, 2011, 07:52:29 AM »

I have posted about this several times so most here know my take on this. There will be no comparison. The 4107 6v92ta will take off like a hot rod compared to the Eagle with the 8v71. That for me that is not the biggest benefit. After to many +8% grades over 10k ft., I longed for a turbo. You would be amazed how just a few thousand feet changes the performance of an naturally aspirated engine. Lots of smoke, heat, poor fuel mileage, and no power. I have driven both engines in a 4106 for a side by side comparison, and if I ever re-power my bus, it will be with the 6v92ta.
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L. Christley - W3EYE Amateur Extra
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« Reply #10 on: March 02, 2011, 08:48:33 AM »

Not trying to high jack the thread here Smiley but I have a 1990 MCI classic with 6V92TA and Allison VR-731 tranny with retarder.

Would that swap out well into a 1970 GMC PD4905 Bus?  and would it be worth it?

Rick
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« Reply #11 on: March 02, 2011, 10:12:13 AM »

Rick,

The 6V92 out of the MCI is going to be a right hand rotation engine, you need a left hand engine for the 4905.

Brandon
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1980 GMC H8H-649  8V71/V730 Marion,NC

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JackConrad
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« Reply #12 on: March 02, 2011, 11:21:31 AM »

Not sure what model a 1990 Classic MCI is, but if it is a T drive, like all the MCIs I have seen, it will not have a VR731 transmission.  Jack
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« Reply #13 on: March 02, 2011, 11:28:15 AM »

MCI Classic is an updated GM Fishbowl, sold to MCI in 1987.

Brian
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Cary and Don
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« Reply #14 on: March 02, 2011, 11:53:49 AM »

We have a 8v92ta in a Neoplan AN340.  Our thought is to put it in a 73 05 Eagle and make it mechanical.   How do you tell if the turbo is center or rear mount? Is there any way to tell if the 8v71 in the Eagle can have a turbo installed without doing all that engine work?  Will the tag on the engine tell which engine it is? Will an inspection tell you?  The 8v71 engine has about 25K miles on it since a complete rebuild done in the early 90's.

Don and Cary
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« Reply #15 on: March 02, 2011, 12:08:21 PM »

I have heard my 8-71 called the dragonfly several times. Fly down one hill, and drag up the next. I know this does not help but thought it very true!!
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« Reply #16 on: March 02, 2011, 02:18:16 PM »

Jack,

My MCI has the V Drive.  It looks like a transit bus but only has a front door. No rear door. Oh, and can it do about 72mph. The paper work calls it a "Suburban Cruiser" also know as the "Classic".   No real storage space to speak of and so I've been shopping for another bus. May be picking up a 1970 GMC PD4905 with the 8V71 and V730D tranny.

Rick
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« Reply #17 on: March 02, 2011, 02:32:03 PM »

Rick,

This is what I get for ASSuming! Shocked  If your MCI is a V-drive, then it probably will go right in the 4905.
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1980 GMC H8H-649  8V71/V730 Marion,NC

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« Reply #18 on: March 02, 2011, 02:49:58 PM »

brando,

No problem here Smiley.  I want to explore all possibilities before I jump in.  Don't want to explain to the boss (wife) why I need a third bus lol Smiley

Rick
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JackConrad
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« Reply #19 on: March 02, 2011, 04:44:56 PM »

Jack,
My MCI has the V Drive.  It looks like a transit bus but only has a front door. No rear door. Oh, and can it do about 72mph. The paper work calls it a "Suburban Cruiser" also know as the "Classic".   No real storage space to speak of and so I've been shopping for another bus. May be picking up a 1970 GMC PD4905 with the 8V71 and V730D tranny.
Rick


OK, I learned something new today.  Thanks for the information.  Jack
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« Reply #20 on: March 02, 2011, 05:09:31 PM »

After turbocharging my 8V-71 with air to air intercooler, now pulling a hill at any altitude, usually clear exhaust and no power reduction.  When over 8,000ft, will get a bit of smoke, but hardly worth mentioning.  The 71 series is much stronger then the 92 series.  71 series is less prone to head cracking, won't leak because of dry cylinder linings, and with 80 injectors will put out 400hp and 1200lb/ft torque-more then a 6V-92TA will be able to stay together putting out.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #21 on: March 02, 2011, 08:30:41 PM »

These are not right or wrong answers, but good, better, best situations. It all boils down to money, the more of it you have the better you can have. If you have the funds, build the 8v71 turbo like TomC did, if not go the other way. Regardless of how much more durable the 8v71 is, we are putting our engines in bus conversions, and they see far fewer miles compared to what they were designed for. If the 92 series holds up well enough in transit service then it would hold up more than just fine for my application. BTW, for V drive owners I don't think 400hp would be a good thing.
« Last Edit: March 03, 2011, 07:49:36 AM by Barn Owl » Logged

L. Christley - W3EYE Amateur Extra
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« Reply #22 on: March 02, 2011, 09:03:02 PM »

Rick -

The powertrain out of your MCI muzzle-loader will work fine in a 4905.

The difference will be 102" vs 96" width, so you'll have to swap cradles.  Some other adjustments will also have to be made, like radiator fan shroud spacing, etc.

I'd use the MCI radiator if it's bigger (thicker) than the one in the '05 and you can shoehorn it in.

Is the MCI's 6V a DDEC?  If so, you'll need all the associated wiring for it and the ATEC transmission.

If it's not a DDEC/ATEC combo, then you can easily "hot rod" the 6V to 350 hp, which will be sweet in the 4905.

Would it be worth it?  Tough call.  Do you know the history on both powertrains?  Based on history, you can make the call, as it's a relatively easy swap, compared to some of the others busnuts have done.

FWIW & HTH. . .

 Wink

 
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RJ Long
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