8V71N bus - bad decision?

[luvrbus]

It make no difference HP is for race cars, torque is needed for buses and all hp rating are at sea level on a old Detroit  the higher in altitude the less you have 

[TomC]

As I've said before, turboing an 8V-71 REALLY wakes it up. Don Fairchild turbo'd mine, we kept the same pistons and went with 7G75 injectors. With the custom air to air intercooler, bigger radiator, turbo muffler, bigger air cleaner, auxiliary transmission cooler, went from 300hp with 800lb/ft torque (N65 injectors) to 375hp with 1125lb/ft torque. If you rebuild an 8V-71 to turbo specs, 7G80 injectors will get 400hp and 1,200lb/ft torque-which was the last horsepower rating Detroit had on it's 8V-71TA. Good Luck, TomC

[luvrbus]

As I've said before, turboing an 8V-71 REALLY wakes it up. Don Fairchild turbo'd mine, we kept the same pistons and went with 7G75 injectors. With the custom air to air intercooler, bigger radiator, turbo muffler, bigger air cleaner, auxiliary transmission cooler, went from 300hp with 800lb/ft torque (N65 injectors) to 375hp with 1125lb/ft torque. If you rebuild an 8V-71 to turbo specs, 7G80 injectors will get 400hp and 1,200lb/ft torque-which was the last horsepower rating Detroit had on it's 8V-71TA. Good Luck, TomC

Yep and you get the same torque from a 6v92 with 350 hp

[DoubleEagle]

It's all a question of cost. If all you can afford is a stock 8V71N that runs well, it will get you there a little slower than the latest and greatest, but it will be simpler to maintain, and will sound cool. In flat land running there won't be much difference, but there are limits to what you can do in the mountains. I have been on local routes out west that got me down to first gear wondering if I was going to make it over the top, so having a tiny bit extra power might be nice if you are adventurous.

[luvrbus]

It's all a question of cost. If all you can afford is a stock 8V71N that runs well, it will get you there a little slower than the latest and greatest, but it will be simpler to maintain, and will sound cool. In flat land running there won't be much difference, but there are limits to what you can do in the mountains. I have been on local routes out west that got me down to first gear wondering if I was going to make it over the top, so having a tiny bit extra power might be nice if you are adventurous.

So true I have saw buses in Colorado with 8v71N/A engines at over 9000 ft they just could not make it to the 9800 ft level with plenty of black smoke and going no where

[Geoff]

Yep and you get the same torque from a 6v92 with 350 hp

Tom is happy with his souped-up engine, but changing out to a 6V92TA  @ 350 HP would of been cheaper.

--Geoff

[lostagain]

Back in the 70s and 80s, all we had was 8V71N engines with 4 speed manual transmissions. We drove them everywhere in the Canadian Rockies, slowly by today's standards, but we got where we needed to go, loaded like rented mules.

A 8V71 will still get you around today.

A 6V92TA like I have in my 5C is a little faster (350 hp, 1050 lb/ft). Enough to pass most trucks up the hills. And not affected by altitude.

This weekend, I am driving a MCI DL3 with DD Series 60 12.7 liter and Allison B500. Hauls @$#. Goes up the hills with the cars. Shifts through the gears without help, unlike an HT740 that you have to shift manually so it doesn't bog down.

They are all available on the used market. You get what you pay for. But don't be afraid of the 8V71. If in good shape, it is a great engine that will get you there and back. And sound a lot nicer than a S60...

JC

[windtrader]

Thanks y'all for your comments, smashed the creepy doubt about the 8v71N motor!

Clifford - That was might thought, these things were the workhorse in the day shuttling passengers from coast to coast. Maybe that was OK in the day when a daily newspaper was OK too. Now, if response is not received in seconds, everyone is all freaked out. I'm hearing they are going to wire a smarthphone directly to your brains so you get instant responses.

Kyle - I get the compromise formula. My first choice is a mid 90's MCI Series 60, plenty of time and money to do a custom conversion. Compromise = 60-70's already converted coach. Not saying anything negative, just quite a compromise.

Utah - Yep, performance costs.

Daddysgirl, LostAgain, etal. - Thanks for the reassuring words.

Geoff/TomC - Like Utah says - More power can do = more $$$. Back to Kyle's "It's all a compromise" I've heard the numbers in doing a TA upgrade on the 71. Entirely different conversation and analysis with that much different budget.

RJ - If folks find a 6v71 makes the grade so to speak, it'll be like the old days when we cruised all over in a VW bus, often chugging up in the slow lane. Been there, done that! LOL. And we always very much enjoyed the journeys and the destination!. And no A/C to boot.

DoubleEagle - Hey, as long as it gets over the top, I'll be happy. Just plan on watching an extra hour of Fox News while on the grade. JK.

[kyle4501]

"125 (degrees) above ambient" -- that is something Detroit used to say but it never made any sense to me.  Ambient temperature is defined as the current outside temperature.  So as long as it is no more than 75f outside you can add the 125 degrees and you are at 200f.  If it is 90 degrees outside that formula would put you at 215f, which is far too hot for a Detroit engine.  Am I doing something wrong or is this formula flawed?

--Geoff

Nope, the formula isn't flawed, it is a useful diagnostic tool.

If you are having cooling issues below 80 F, there is a problem with the cooling system.
However, if you are having cooling issues only when it is above 80 F and you are at full throttle, the solution is as simple as reducing how much power you are using. 

I suppose additional cooling capacity could be added to decrease the temp rise above ambient. But, I don't see a need to do that since 190 is as high as I have seen mine get. I may reconsider if I have to deal with any real grades . . . . . .

[Geoff]

I'm sorry, but I don't see it as useful for anything.  The original question to "the formula" was "How hot can you let your Detroit get before it's time to stop?".

--Geoff

Nope, the formula isn't flawed, it is a useful diagnostic tool.

If you are having cooling issues below 80 F, there is a problem with the cooling system.
However, if you are having cooling issues only when it is above 80 F and you are at full throttle, the solution is as simple as reducing how much power you are using. 

I suppose additional cooling capacity could be added to decrease the temp rise above ambient. But, I don't see a need to do that since 190 is as high as I have seen mine get. I may reconsider if I have to deal with any real grades . . . . . .

[DoubleEagle]

DoubleEagle - Hey, as long as it gets over the top, I'll be happy. Just plan on watching an extra hour of Fox News while on the grade. JK.

I should also mention that there are some grades that the 8V71N can barely climb in 1st gear with the 4 speed Spicer. For instance, the steep grade to the entrance of the Crazy Horse Monument in South Dakota (elevation about 6000 ft.). When I went there, I was loaded with extra fuel and water pulling a 4X4 (Model 05 Eagle), and I was steadily going down through the gears to 1st. There were a couple cars ahead of me, and if either one stopped or slowed down I would not have made it. In 1st I was able to go up to governor (2050) at first, but the rpm's kept going down to the point of lugging when I finally made the turn at the top to the parking lot. If the turn had been another 50 ft up, I do not think I would have made it. I would have had to unhook the 4X4, drain water out, throw passengers off, put heavy tools in the 4X4, and then back down the mountain to make another run at it. Trying to restart in the same spot after stopping would have fried the clutch. An Allison HT740 automatic would probably have done alright. Once you venture off Interstates with known grades, you have to know your limitations. 

[kyle4501]

I'm sorry, but I don't see it as useful for anything.  The original question to "the formula" was "How hot can you let your Detroit get before it's time to stop?".

--Geoff

Some say water temp of 210F will kill it.

To me, it is useful to correlate ambient temp to potential overheating.
So many have overheating issues & don't know why or where to start - or just assume that that is the way it is. Knowing what the capacity of the cooling system is ( should be ) would be very useful information if one is having temperature issues, but that is just my opinion.

I wasn't clear, this is "the formula" that Newell supplied with my coach when it was new. According to Newell, it was the result of extensive testing with Detroit diesel. So, for me, it is usefull to know the heat rejection capacity of the cooling system for a 475HP 8v92 as designed by Newell. I suspect that the 125F temp rise was a compromise of radiator capacity vs cost vs space available.

I was only trying to make the point that there is a limit to any cooling system. Only testing will reveal what the steady state full load temp rise is in any given system.

All bets are off for customized systems that have not been tested as such. Same goes for any system that has not had proper maintenance.

[easystreet]

It really does come down to what we each individually want, can afford, and in the end are willing to live with. Me, I'll be happy to have our families 3751 w/6-71 back on the road and enjoy it in the speed and parameters that some great engineers designed it to operate within. I'm content to see the world thru the windshield at a slower speed and maybe experience a little bit more of that era. In my book faster is not always better. 8v71Nat were a great engine. Sure T's and TA's have more power, but nothing sounds like an N engine in the exhaust. Welcome to the world of buses and many differing opinions from a lot of great folks.    

[windtrader]

2xEagle - At this point, it'll be at the start a life with an 8V71N as that is the plant in the bus conversions for my budget. Might there be a 1000+ ft/lb. torque mill in the future, sure but who knows what the destiny of ones journey of life.

[windtrader]

@easystreet - Thanks for the perspective, one which I must prescribe to =enjoy the journey, ala Dave5c and others.