Performance 8V71

[Handyjim]

What kind of performance can I expect with a MCI 7 Bus Conversion
with a 8V71 Engine through an Allison 740 HD?  Wondering how it would do on grades.  I'm new to the board, and in the early info-gathering mode.

Jim Corey

[Zeroclearance]

While there are many my "senior" out there driving the "7's"   In the 80's I spend many late hours behind the wheel of a "7"...

We did every mod that we could with timing and injectors and had to upgrade to larger radiators and in the end, we wanted more power.   

At the very least try to look for a turbo 8V71 or look at the guys that have installed 8V92T's..     

[RJ]

Jim -

Remember the Aesop Fable about The Tortoise and the Hare?

Well, that's the difference between your car and a bus when it comes to pulling grades.

In a nutshell, with the stock powertrain you're asking about, you will have to downshift to at least 3rd, and often 2nd, when pulling 4, 5 & 6% grades.

The coach will pull all day at 1900 in 2nd gear, at about 30 mph, on 6% grades, but make sure you keep your eye on the temp gauges.

You'd need a 500+ hp engine if you want to go faster, but that takes big bucks for minimum return, and not really economically viable in that old a chassis.

The 8V71N / HT-740 powertrain is one Greyhound used for years - it's virtually unbreakable with proper maintenance and correct driving techniques.

Since you're gathering info, use the "search" function this board offers.  Lots of info here, many of your questions have already been answered.  Also be sure to check out www.busnut.com, which has got an incredible archive of info.  They are suffering an ISP glitch right now, but Ian will have it running smoothly again shortly.

FWIW & HTH. . .

[Chopper Scott]

I have a 7 with the same combo that you are asking about. Having some heating issues I inquired on the board and found out a lot of info from the likes of Jack Conrad and others. It seems the 7's with the Allisons have heating problems because of the added heat that the Allison makes that is cooled through the motor. Recomendations were having the radiators redone, adding a tranny cooler, making sure the seals etc surrounding the radiators and fan doors were good, making sure the cones in the fan shrouds were good, no mud flaps at the rear of the bus, installing some kind of openings in the side doors to help exit the air and even changing the pulley on the fan gearbox to speed up the fans. Right away I found the seals around the radiators were non existant however the radiators had been redone by the PO. I also redid the seals on the fan door. On high idle it will suck the hat off my head now! I cut openings in the side doors and installed screens also. That pretty well cured my problems but I really haven't put it to much of a test. I have installed a tranny cooler as of late and am hoping that will basically eliminate my problems. As far as power there is never enough but I didn't buy this monster to be in a hurry. That's what I'm getting away from! I would think that adding any more hp to this setup would have to include some major cooling upgrades.

[Chopper Scott]

By the way..... Welcome!!!! Hope you get the disease we all got!

[johns4104s]

There are a lot of people that know a lot more than me on this board but from what i can gather the old 71 and 92 series engines need to be worked hard ran hot 185/190 deg, when you put them in a MCI the 8v71 and 6v92 are a little under powered but run hard and hot and do the job well. The 8v92T has lots of power but the way we run our buses does not get up and stay up to the correct temperatures.
Just my 2 cents worth.

John

[Handyjim]

Thanks you all!

I will use the search function, particularly as I learn enough to know what to search.  Hate to ask the same questions over and over.

Don't know about the bus bug.  Wife was slipping some kind of vaccine into my coffee.

[Lonnie time to go]

There are a lot of people that know a lot more than me on this board but from what i can gather the old 71 and 92 series engines need to be worked hard ran hot 185/190 deg, when you put them in a MCI the 8v71 and 6v92 are a little under powered but run hard and hot and do the job well. The 8v92T has lots of power but the way we run our buses does not get up and stay up to the correct temperatures.
Just my 2 cents worth.

John

The 8v92T has lots of power but the way we run our buses does not get up and stay up to the correct temperatures.

Can you explain why

Lonnie

[TomC]

John-replace both thermostats.  Good Luck, TomC

[bobsw]

I have 3 radiators and a trany cooler on my 7 with a 8-92 and I don't have a problem running up to temp.

[johns4104s]

bob,
What temperarure do you run yours at?

John