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Old 06-04-2022, 10:00 AM   #1
Mini-Skoolie
 
Join Date: Aug 2019
Location: New Hampshire
Posts: 20
Picking up my MCI

Figured I should make a post. Heading to pick up our 71' MCI 7 tomorrow. Already converted years ago so we'll be redoing it. I'll try an keep this thread up to date but you can also follow the build here ..
https://www.youtube.com/channel/UCWIWkhVLIHfLHzzdtQiFzfA

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Old 06-04-2022, 10:28 AM   #2
Bus Nut
 
Tejon7's Avatar
 
Join Date: Mar 2020
Location: Western MT
Posts: 632
Year: 1990
Chassis: Crown Supercoach
Engine: Detroit 6-71TA, 10 sp.
Rated Cap: 90 (40')
Looks good, sounds even better!
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Old 06-04-2022, 10:30 AM   #3
Mini-Skoolie
 
Join Date: Aug 2019
Location: New Hampshire
Posts: 20
Quote:
Originally Posted by Tejon7 View Post
Looks good, sounds even better!
Thank you, we are very excited!
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Old 06-04-2022, 08:02 PM   #4
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,381
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Welcome to the world of two-stroke diesels! If you are not familiar with the care and watering of those beasts, I recommend that you read all you can about how to drive them and what to do / not to do to them, and what oil is needed for their continued good health. Folk who are unaware of these basic ground rules, or who think they're not important, will eventually have a very expensive surprise one day when the engine says "Enough of this".

My friend Mike, who occasionally posts here under the name Crown_Guy, has a wealth of knowledge of and real-world experience with Detroits, so if he says something it's worth listening to what he has to say! The shortened version is "1) Don't lug them, 2) Don't ever overheat them, and 3) Only use CF-2 rated straight 40-weight oil".

Good luck, John
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Old 06-04-2022, 09:14 PM   #5
Bus Nut
 
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Join Date: Dec 2013
Location: SoCal
Posts: 392
Year: 1989
Coachwork: Crown Coach
Chassis: 40ft 3-axle 10spd O/D, Factory A/C
Engine: 300hp Cummins 855
Rated Cap: 91
I don't know if thought it was a real Greyhound Company bus, or just the generic "Greyhound" type highway Coach. But I can confirm that it was indeed a real Greyhound Company Intercity Coach. The giveaway, for those that can't see it, is that 10" square opening door/panel on the left side just behind the driver under the windows. That was opened while the bus was in a Terminal waiting on passengers to be loaded and they would plug in a large hose carrying Cold air from the buildings' A/C system. This allowed them to shut the bus off, which both saved fuel, stopped the exhaust fumes, and also meant no A/C cold air from that bus running it's A/C. They could load passengers and wait to depart in comfort and lower noise and smell comfort. Only the Greyhound Company MC7, 8's, 9's etc., had that door and capability installed as an option. It was plumbed directly into the bus air conditioning duct-work inside.

Someone went to a lot of trouble to convert that from the original 8V-71 and 4spd manual Spicer to what it is today. That's obviously a Turbocharged 6V-92 with an Allison HT740 4spd automatic. John, above knows all about this as well, since his Crown II has that exact drive-train. The magnificent Coach Drive-Train used on highway coaches.

It may actually have not been too much trouble since the engine/trans power pack in the MCI is mounted to a sub-frame that easily slides out to the rear for easy engine swaps thus keeping the coach in service and making revenue. The 6V-92T/HT740 was the de-facto standard for many, many years in almost all highway buses made by all manufacturers. It would have been fairly easy to have found one as a take out and swapped it into this MC7.

As long as it was done cleanly and all mounts and accessory items were properly seen to it would be a very solid and reliable upgrade. The one thing to be very cautious about is the original twin radiators in the MC7's could barely keep the non-turbo'd 8V-71's cooled when the ambient temperature climbed much above 90 degrees. They were forever having trouble staying cool and the fixes were usually never good enough to keep up with the heat here in the Pacific Southwest.

MCI is a Canadian company and they were designed originally for the Great White North climate. When they started getting used by Greyhound in the 70s, (and the MC7 was the first 40ft model in mass use) they were immediately shown to have a persistent overheating problem that required very diligent monitoring by the drivers to keep from burning up the engines.

Until you gain experience with your particular bus I'd take the time to check out the cooling system thoroughly and see if there have been any upgrade modifications made to accommodate that 6V-92T higher heat rejection rate than the original 8V-71. If not I think you're going to find it will tend to overheat and could cause some very expensive repair costs if you don't drive it properly.

Be very careful initially until you see how it drives and the heat as it builds up. It's counterintuitive when you drive the Detroit 2-strokes since you must drive them hard with your foot to the floor while accelerating, like you're made at it, that's the correct way to drive them all. BUT with a potential over-heating issue this will add to the problem so you need to baby it along. Like I said a contradictory set of issues to be dealt with. First you MUST make sure the cooling system is working and up to the task in all weather climates, highway terrain, and the load being carried on the bus. After that's fixed then you can start driving the 2-stroke the way it needs to be driven.

Another real problem is that the normal Allison Auto installation was to have the transmission oil cooled by an inter-cooler using the engine water cooling system, and this added heat was also sent to the main engine radiators. This extra heat load was way too much for the original radiator cores and the airflow pulled through them. A real source for uncontrolled overheating.

Again, if it was modified when it was upgraded to the 6V-92T you should be able to find it yourself, or look around for someone familiar with the MCI's, and they should be able to check it out and offer suggestions for how to keep things cool.

First place to start would be a totally separate Transmission oil cooler that doesn't use the main engine coolant loop. Another is to see about getting the thicker radiator cores that came along in the later years from MCI, and even a different pulley on the squirrel cage blower to turn it faster. Also you want to Completely Seal the radiator plenum chamber above the engine. ALL the air HAS to be pulled in through the twin radiator cores. Any air leaks will compromise this and reduce the air flow through the cores.

You're in for an adventure for sure and I'd suggest checking out the other forums where they own and convert Coaches. They will be much more able to help you with your MC7 than the few here who have experience.

busconversionmagazine.com is one place to start. There are others but they do coaches and conversions there and can help you out.

If you have questions you can contact me direct. I'll send you my info in this sites PM system, but many don't see it as working very well. You can check out my previous posts where I've given my email and cel# too. John can help you too with your cooling issues since he had to deal with them on his Crown II.
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Old 06-04-2022, 11:04 PM   #6
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,381
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
My Super II had persistant cooling problems that were getting worse each year, so a few years ago I replaced the entire cooling system instead of faffing about with one thing at a time. I had Atlas Radiator in Santa Fe Springs CA make a new 6-row high-efficiency core that was slightly larger, and the clunky old metal fan was replaced by a custom 9-blade high-performance fan from Multi-Wing; I had a new hydraulic fan motor made to replace the old one that was leaking internally, and I also replaced the hydraulic/PS pump because its input shaft was worn. I also replaced both thermostats and seals, the fan's hydraulic controller, the coolant temperature sender and hi-temp alarm switch, and moved the hydraulic cooler to a different place that didn't block the radiator's airflow. The transmission fluid is now pre-cooled through a new remote cooler before it enters the engine's heat exchanger, and this helps reduce heatload into the coolant. I also made a radiator mister, actually more a fogger, but I don't think this makes much difference.

As Mike says, driving the bus requires you to constantly watch the temperature gauge (you do have a reliable and accurate one, I hope?). Keep the engine revs at about 2000 when climbing hills in hot weather, shift down to 3rd or even 2nd so the engine isn't lugging, and keep a 3/4 pedal, then you should be OK. If it does want to overheat, take heed from what I did to solve my overheating issues.

Good luck, and watch that temp gauge like a hawk!

John
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Old 06-04-2022, 11:56 PM   #7
Bus Crazy
 
Join Date: Oct 2020
Location: Near Flagstaff AZ
Posts: 1,951
Year: 1974
Coachwork: Crown
Chassis: "Atomic"
Engine: DD 8V71
Welcome to the club! As both of my friends John and Mike said...watch the heat. Our MC-7 (a 1974) was also upgraded to a 6V92TA with an automatic and I definitely need to address the potential to overheat. As they said, the original radiators were just barely enough for the original 8v71...with the 6V92TA they cannot keep up.
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Old 06-05-2022, 04:12 PM   #8
Mini-Skoolie
 
Join Date: Aug 2019
Location: New Hampshire
Posts: 20
Well we made it...350ish miles. Everything seems to work as it should. Have an issue with the tag bags not pressurizing evenly? Driver's side is over pressurizing. I'll dig into it further in the near future. Temp topped about 185
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Old 06-15-2022, 02:54 PM   #9
Mini-Skoolie
 
Join Date: Feb 2022
Posts: 33
Near each air bag is a "Leveling" switch. If one is not set properly, a bag can under/over inflate making the coach uneven. My bus is a MCI 8 - original 8V71NA with auto transmission. Climbing the hills into Flagstaff, AZ (going E to W), the coach started to overheat -- back off the throttle and made it okay (but slow). Took the bus in to a Detroit Dealer in Flagstaff and two old timers (that worked on these old engines) got out a hand held digital thermometer and checked around the cooling system They determined that the thermostats were not working properly and only 1/2 of one of the radiators was working. After they finished working on the bus -- never had another issue. Wish my bus had the drive train yours has - maybe I'd still be running it. Right now it is used as an 'apartment' for visitors.
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