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Author Topic: 8v71 power  (Read 7701 times)

Offline Cary and Don

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8v71 power
« on: February 28, 2011, 05:09:17 PM »
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
GMC4107
Neoplan AN340
1973 05 Eagle
Neoplan AN340

Offline luvrbus

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Re: 8v71 power
« Reply #1 on: February 28, 2011, 05:40:06 PM »
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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Offline gus

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Re: 8v71 power
« Reply #2 on: February 28, 2011, 07:42:56 PM »
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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Offline Cary and Don

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Re: 8v71 power
« Reply #3 on: February 28, 2011, 08:12:00 PM »
Do they ever put on turbos without blowers? 

Don and Cary
GMC4107
Neoplan AN340
1973 05 Eagle
Neoplan AN340

Offline lostagain

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Re: 8v71 power
« Reply #4 on: February 28, 2011, 08:18:17 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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Offline Cary and Don

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Re: 8v71 power
« Reply #5 on: February 28, 2011, 08:24:54 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
GMC4107
Neoplan AN340
1973 05 Eagle
Neoplan AN340

Offline lostagain

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Re: 8v71 power
« Reply #6 on: February 28, 2011, 08:31:49 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
JC
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1977 MC5C, 6V92/HT740

Offline MCI-RICK

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Re: 8v71 power
« Reply #7 on: March 02, 2011, 07:41:35 AM »
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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Offline lostagain

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Re: 8v71 power
« Reply #8 on: March 02, 2011, 01:44:38 PM »
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
JC
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1977 MC5C, 6V92/HT740

Offline Barn Owl

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Re: 8v71 power
« Reply #9 on: March 02, 2011, 03:52:29 PM »
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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Offline MCI-RICK

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Re: 8v71 power
« Reply #10 on: March 02, 2011, 04:48:33 PM »
Not trying to high jack the thread here :) 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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Offline brando4905

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Re: 8v71 power
« Reply #11 on: March 02, 2011, 06:12:13 PM »
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
1980 GMC H8H-649  8V71/V730 Marion,NC

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Offline JackConrad

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Re: 8v71 power
« Reply #12 on: March 02, 2011, 07:21:31 PM »
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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Offline bevans6

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Re: 8v71 power
« Reply #13 on: March 02, 2011, 07:28:15 PM »
MCI Classic is an updated GM Fishbowl, sold to MCI in 1987.

Brian
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Offline Cary and Don

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Re: 8v71 power
« Reply #14 on: March 02, 2011, 07:53:49 PM »
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
GMC4107
Neoplan AN340
1973 05 Eagle
Neoplan AN340