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Author Topic: How much to increase HP on 8V71  (Read 5316 times)
robertglines1
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« Reply #15 on: September 23, 2010, 06:50:36 PM »

do you have a tach? what top rpm you turn?does trans (auto)downshift between 1600 and 1800 rpm? where does it upshift?
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #16 on: September 23, 2010, 06:57:39 PM »

The cheapest thing you can do is get an experienced busnut to take your coach for a drive and see what comes of that.

Why spend money and end up with the same results?

happy coaching!
buswarrior
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Stolaas
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« Reply #17 on: September 23, 2010, 07:58:28 PM »

Any busnuts live near Huntsville  Roll Eyes

I wish I had a tach. I have no idea what my rpm's are.

I don't think I have seen any smoke lately. I used to when I first got it and was getting to reading my rpm by the color of the smoke lol  Cheesy  It upshifts nicely but I have to manually down shift or any sligt grade as it won't do it itself without bogging down.

The more I read and your comment is getting me excited to change the filter.   That is after I take out trip to new England for two weeks in our dodge that we were originally going to do in the coach  Embarrassed

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OneLapper
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« Reply #18 on: September 23, 2010, 08:05:18 PM »

Stolaas,

I just swapped injectors on my 8V71.  The replacement engine had N55 (I never ran the bus with these injectors) and I installed N65's and changed the cams to "A timing".  I have to admit, the injectors where nothing to change compared to the cam timing!  Now for cost: rebuilt injectors from the DD dealer were $75 each, but the labor to pull the engine and tranny, remove flywheel, back engine cover and then change the timing will set you back 2 or $3k.  It's a big job on a big engine!  I did the work myself, made a few mistakes, but corrected them.  I had that back cover off three times and the flywheel off twice!!!

Could I feel the difference in my 4106 from the tired, smoking, N60 STD timed, 2100 rpm engine compared to the fresh, non-smoking, N65 A timed, 2450 rpm engine?  OH Yeah!  I'm now able to take hills in 3rd gear at 50 that I was previously using 2nd gear at 35 on the governor.  Fuel mileage went from 10.8 mpg to 8.2, but appears to be getting better now that I'm not drunk with HP and attacking every hill I see at 75!  It's getting around 9 mpg at 70mph.

Hope this helps!
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OneLapper
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« Reply #19 on: September 23, 2010, 08:38:54 PM »

Stolaas, do you have any idea what injector is in the engine,you have a engine that will give you a little over 300 hp tops without spending tons of cash to get more then you will have the heat to deal with just have the old 871 tuned up and it will serve you well not a race horse but it will bring you home.
The A timing on a 8v71 in a bus is a waste of time that was designed for trucks it is not going to help you with a automatic or a 4 speed transmission in a bus only gives you more black smoke and less MPG

good luck
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RJ
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« Reply #20 on: September 23, 2010, 11:08:30 PM »

Stolaas -

"That is after I take out trip to new England for two weeks in our dodge that we were originally going to do in the coach."

Why not take the coach???


"I wish I had a tach. I have no idea what my rpm's are."

You don't need a tach, all you need is a working speedometer.  Take your coach out on a local straight back road.  From rest, start in low gear, wind it to the governor, and hold the speed for a few seconds while you make a mental note.  Stop & write it down.  Do the same for 2nd & 3rd.  Armed with this info, plus some white out, white nail polish or similar, put a drop on the speedometer face that corresponds to the top speed in each of the lower gears.  Now that you know your shift points, read the following, especially near the bottom:

http://www.busnut.com/bbs/messages/12262/16204.html?1167073154

If you're speedometer's not working and you're using a GPS to monitor your speed, just put something on the dash with the shift points for reference.  By shifting the automatic manually, you'll find that it's a much more pleasing ride.  (No need to manually start out in first - that's the stump puller.  Manually starting in second is fine with the 740.)


"The more I read and your comment is getting me excited to change the filter."

Changing the fuel filters is about a 15 - 20 minute job, easily done before you take the coach out to check the various shift points as suggested above.  Just make sure you fill the new filters with clean diesel before reinstalling.  Also, do one at a time so you don't lose prime.

As Clifford said, the 8V71 will serve you well.  Thousands of Greyhounds and others used this engine for over 20 years in revenue service, 99% of which were probably set up the same way as your coach. 

Aesop's Fable!!!

FWIW & HTH. . .

 Wink

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RJ Long
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TomC
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« Reply #21 on: September 23, 2010, 11:13:37 PM »

When I first bought my transit, I had the rear end ratio changed from 5.57 to 4.56 and the injectors changed from N55 to brown tag N65's.  Decent performance at sea level, but unacceptable black smoke and lack of power above 5,000ft (go to Mammoth at 8,300ft).  I then decided to turbo my 8V-71.
I first had a custom air to air intercooler made (I have about 8 inches between my radiator and edge of bus), had Don Fairchild install the turbo, and hook it up, increase the injectors to 9G75's (300hp to 375hp, 800lb/ft torque to 1125lb/ft torque), bypass valve kit on the blower, fuel modulator (to prevent the injectors from opening up before turbo boost-cuts down on black smoke).  Then ultimately enlarged the radiator, air cleaner, muffler. Installed an auxiliary transmission cooler, cut additional vents into the back engine door, and installed 15 misters on the radiator (no room for a bigger radiator, and have the biggest core installed).  Cost- $11,000.00. Worth it, no more smoke at altitude, nor loss of power at altitude either.  The fuel mileage is the same, but performance is drastically different.  It is a pleasure to drive-now don't have bad thoughts of getting stuck with the extra power.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #22 on: September 24, 2010, 04:43:47 AM »

You have some great advice from those that know! Take some time to re-read these posts, make a plan for how you want to tackle it and go for it.

RJ's mention about that article is one to memorize and not forget!

Stop and smell the roses and head for the hills! That ole pile of metal will serve you well!

I love my ole 8V71N, it has been good to me. It has never let me down and I'm not in a hurry to get somewhere anyway, I just know I'll get there. I have never had a heating issue either. Keep the ole gal wound up and she will treat you right! Wink

Paul
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Becky and Paul Lawry, On The Road
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prevost82
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« Reply #23 on: September 24, 2010, 02:31:47 PM »


The more I read and your comment is getting me excited to change the filter.  

Changing the fuel filter will do little, if anything, if your filter was that bad you'd notice it on the flat. The 8V71N suck in hill country, if you're living in the flatlands they're fine or if you don't mind going up a hill at 25 to 30 MPH for 1/2 hr, with the motor screaming, it will work for you.
When I bought my bus (seated in Cal) I drove it to BC and had two major passes to go over and thats the speed I was going. Worse yet, there's 3 roads out of the town I live in that are 6% grade, so I'd be crawling every time I left town, I couldn't live if the 8V71.

I took out the 8V71N (sold it) and installed a 500hp 8V92TA (used with 50K on it) with a 6 speed manual and never regretted it. I also pull a diesel PU about the same weight as yours .... and I never drop below 55 MPH on a 6% to 7% grade. If I did it again ... I think I'd put in a ISM 450 HP with a 10sp autoshift.
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Stolaas
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« Reply #24 on: September 24, 2010, 09:14:41 PM »

I would love to have the 8v92 in mine!!!

But I can't work on the bus engine in any magnitude (live in a community) so it would be all at a garage and I don't think I can afford that.  Huh

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Charles in SC
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« Reply #25 on: September 25, 2010, 08:16:37 AM »

I have been up and down the hill of which you speak. I would say your bus is running fine but it would still be good to get another bus nut to go ride with you. And change the filters just because it has been a long time. The first trip of any length I took involved Monteagle mountain. I thought I burnt my breaks up but it was just some old grease that was on the outside of the drums. That is part of the pucker factor involved with making friends with a new bus.
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S8M 5303 built in 1969, converted in 2000
Stolaas
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« Reply #26 on: September 25, 2010, 04:12:19 PM »

Yea it just really shocked me.  I would normally drive up that hill at about those speeds with the 5th wheel but i always had power to spare.  Just didn't feel right having to have it on the floor with no power reserve on such a small hill.

Charles, if you have Been on mountesano (hwy 431) then you may of gone up the 6% grade at the south end of guntersville  not looking forward to that one.  I think I could get out and walk up it fast haha
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Charles in SC
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« Reply #27 on: September 25, 2010, 05:07:40 PM »

The % of the grade is only part of the equation. The other part is the length of the incline. We have one close to me that is a 7% but it is short. Right after it is one that is not steep enough to be labled but it is loooong and will cause more trouble.
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S8M 5303 built in 1969, converted in 2000
ojgetaway32
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« Reply #28 on: September 28, 2010, 06:20:57 AM »

Everyone stop and re-read RJs post.  Don't adjust the timing or change injectors, adjust your thinking and change your expectations...
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Josh Miller, Attorney, hockey player, son, brother, friend and busnut...
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prevost82
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« Reply #29 on: September 28, 2010, 12:07:06 PM »

I would love to have the 8v92 in mine!!!

But I can't work on the bus engine in any magnitude (live in a community) so it would be all at a garage and I don't think I can afford that.  Huh



It was a 2 day swap for me .... and the 8V92 cost me around 2500 after I sold the good running 8V71 (a charter company bought it) .. so it wasn't that bad, but I don't have a MCI, so I did'n't have any cooling issues to add costs.
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