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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: cutnhorse on February 26, 2022, 08:49:24 PM
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thinking of putting in a 8v92 in a mci 8 , putting a ht 754 behind it does this fit for length anyone know in a model 8
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What's your plan for cooling upgrades?
Fitting won't be your problem.
Happy coaching!
Buswarrior
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Had a friend that had Leid Diesel upgrade his MC8 new conversion upgrade to 8V92 from 8V71. Gained 10mph on our 7 mountain grade. He did complain that mpg dropped from 6 to 8 to 4 to 5. Ht740. Never heard whether he had heatingvproblems, but probably. Expensive to upgrade to larger radiators and blowers. May make more sense to go with a 60 series.
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thinking of either using the 102 rad or removing the squirel cage fans , putting a truck rad down on the side putting a angle gear box on it saw one on ebay done in a 7 person said he used a rad out of a freightliner, does not warm up on grades, any thought would be appreciated , what upgrades can a person do on the blowers, cut mine out to the bigger hole a few years ago, have the smaller pulley on gear box
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Smaller pulley, larger fan exhaust, check.
Condition of cones inside the fan intakes?
How have you got the space around the rads sealed, and how are the fan doors sealed?
The other big MC8 weakness is the engine intake. An old pioneer builder, Fred Hobe, advocated cutting the exterior skin into the cavity between the top of the air cleaner, and that tiny square intake in the radiator cavity. The engine is sucking through a straw, with the stock routing. Rectangular cut, after a small hole to find the edges, and install the mesh of your choice to keep the birds from nesting in it.
Bigger rads involves tearing the back corners out of the interior, to support and box in the larger rads, big job, depending on your skills.
Going the sidwinder fan route, measure the space available, not nearly the space between tag fender and rear bumper as on the newer buses, the rad may have to mount higher up? And same thing, interior has to be torn up to box it in.
Beware that a newer truck radiator may not be capable of cooling a high HP 8V92, 2 reasons, 4 strokes make less heat, and it is sized to be out in the wind, not sidewinder.
Check the BTU ratings closely, the btu of your proposed engine package, the btu of the allison, and the radiator's rating to discard all that. Don't forget the fan size/pitch that you'll need to pull all the air through, again, monster sized. All that work without some engineering decisions and still overheat would be really frustrating.
If fabrication is your gig, and you are going to engineer it right, build it your way, never mind the naysayers!
Happy coaching!
Buswarrior
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If it was me and I were going to go to all that work and time I would go with the series 60 or a Cat C series engines. That 7 that was on Ebay I had a truck mechanic friend that is in the area of were that bus was for sale in, look at it. The motor conversion wasn't all that nice and I would wonder if he had heating issues.
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The 8v92 works in a MCI good if you use the MCI specs for the 8v92 and that is 365 to 400 hp with 1300 ft lbs of torque ,you are not going to install a series 60 or C-cat engine in a MCI 8 without spending a ton of money
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Turbocharging an 8V-71 REALLY wakes it up. I turbocharged my 8V-71 with high compression pistons since it had the clean burning transit bus rings. I added a custom air to air intercooling, turbocharger from an early 12.7 Series 60 with waste gate, changed injectors from N65 to 7G75, by pass valve on blower, bigger air cleaner, bigger muffler, bigger radiator with misters. Went from 300hp at 800lb/ft torque to 375hp and 1125lb/ft torque. Get the same fuel mileage, but much better performance. If you rebuild the 8V-71 to turbo specs, with 7G80 injectors (which was the last version Detroit made) 400hp and 1200lb/ft torque. Good Luck, TomC
I would just stick to the HT740. HT754CR is not as strong as the HT740. My 3406B Caterpillar works just fine with the HT740. I down shift from 4th to 3rd at 1500rpm-perfect for 8V-71 or 92.
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One thing that will REALLY help is to install an air cooled trans cooler.(radiator) instead of running it through your engine coolant.
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The 754CR is match made in heaven for a 8v92 in a bus the close ration without the wide gap between shifting is ideal for the torque band on a 8v92
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In a best case scenario with all the fins clean, rubber seals good and engine turning at 2100rpm, how many CFM do the squirrel cage fans move through the radiators?
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any different gear ratio avaible that do any good on the fuel mileage
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Ratio choice for existing differential doesn't go as far as you'd like for an 8V92 and direct drive Allison. Can't remember, maybe a 3.3? Hard, very hard, to find.
There are busnuts who have flipped suitable axles for coach duty, that have much more suitable taller ratios. Revs down for economical cruising, higher top speed for the times and places one would want that.
Not because it makes economic sence... because of the challenge to source, adapt and build it.
Not every axle is suitable, lubrication running upside down... all the welding, suspension mounts, chamber mounts...
I always thought it a good way to get a locking diff, along the way, if one would withstand being upside down... never did hear of a busnut getting a locker...
Flip it correctly, or it will go very quickly in reverse...
The arrival of overdrive automatics and 4 strokes put an end to the motivation to make an old coach perform like this.
Happy coaching!
Buswarrior
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thinking of putting in a 8v92 in a mci 8
Cutnhorse -
Your MC-8 will climb a 6% sitting on the governor in 2nd gear at about 30-35 mph. Just like practically every bus built from 1945 on.
You can go out and spend several thousands of $$ on an 8V92T and you'll be able to go up that same 6% grade sitting on the governor in 3rd gear at about 45 mph. . .
BUT
Because of the MCI's basic design, you'll spend that whole period of time stressing over the rapidly climbing temperature gauge, hoping you'll crest RockyTop before the engine either shuts down or self-destructs due to overheating. 8V92s do NOT like heat! Especially in a bus!
OTOH, you could take all the $$ that a repower would cost and upgrade the interior to make sure that Mama's happy? 'Cause we all know about Mama not being happy!
Pick your poison?
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I wanted more power out of my 6v92ta and had it up to 350 hp and the only way I could do it for the less cost was to get the coach I have now and sell the old coach . I am happy with the 1875 lbs of tq and all done I have less $$$ in the coach I have now then I had in the MCI
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was thinking of using the rad from the donor firetruck the 8v9e motor comes from its a mechanical 475 horse , using a gear box from a prevost fan, anyone know if the prevost gear box is a 1:1 ratio, using the fan from the firetruck
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I am almost finished a repower. I did every single thing myself and am up to around $30,000. I am OK with that but I would never tell my wife, and the only way I could have saved money is to build some garbage I would not have been proud of.
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was thinking of using the rad from the donor firetruck
That radiator is fine for a truck with the radiator out front.
It will quite possibly be too small for a side-mounted bus application.
The radiator on my 8V92T Prevost is 3' x 3' x 7" thick - and I STILL have to closely monitor the temperature gauge climbing 6% grades.
But it's your coach, your money, so do it your way. . .
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These major heart transplants were sometimes done in the early days of the growing bus conversions fad. In 2020, it is more economical and time-saving to start with a Series 60 bus. They are selling for dirt cheap and would be a far better platform for a new conversion.
There is no free lunch. Sell the MC8, use that to get into an already converted Series 60 bus. Yes, you will have to pony up some extra dollars but it will for sure be less than what you sink into the engine upgrade. You can buy an unconverted bus for less than a converted one, saving you money upfront. Then pay as you DIY conversion. Sill takes time and money but you control both variables. In the end, you get a much better bus platform and a new interior.
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rj
do you know if your prvost is running a fan clutch or does it have a old school fan with no clutch? good point on the fan not having air pushed through.
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These major heart transplants were sometimes done in the early days of the growing bus conversions fad. In 2020, it is more economical and time-saving to start with a Series 60 bus. They are selling for dirt cheap and would be a far better platform for a new conversion.
There is no free lunch. Sell the MC8, use that to get into an already converted Series 60 bus. Yes, you will have to pony up some extra dollars but it will for sure be less than what you sink into the engine upgrade. You can buy an unconverted bus for less than a converted one, saving you money upfront. Then pay as you DIY conversion. Sill takes time and money but you control both variables. In the end, you get a much better bus platform and a new interior.
This is the route I decided on when I bought my bus. Too many advantages to overlook. I've done engine conversions on quite a few smaller vehicles and would have no reason to shy away from one of these but I also know how the domino effect takes over despite your best efforts. The schedule stretches out, the cost goes up, and it takes years to get the performance and driveability you expect to have. Not for the faint hearted, one modification can and usually does cause even more mods on down the line.
Flathead Fords are another older engine that has a great sound and vintage appeal but you rarely see anyone using one as a daily driver or these days even as an occasional driver. Low power, piss poor mileage, overheating issues, any of that sound familiar?
Jim
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Do remember, most busnuts look at this mountain and wonder why anyone would climb it...
Because it is there?
If you want to engineer the dream drivetrain for that bus... is the advice from places that still have enough moxy left to do another one, or is it from places that are too tired, or never would have in the first place?
We can be such a bunch of downers, with all our sage advice...
Climbing rocks makes little sence except to rock climbers.
Build it!!!
Happy coaching!
Buswarrior
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We all like the sound of those old DETROIT engines as well as our favorite car and light truck engines. But we have to remember, sentimentality and nostalgia doesn't propel vehicles. Yes, the old DETROIT 71 and 92 as well as the mentioned FORD FLATHEAD V8 and others were good. But you always have to ask that if they were all that good, then why don't they build them today? My very first car was a 1972 AMC MATADOR with a 5.0L V8 and 150HP. My current car a 2021 NISSAN ALTIMA has 2.5L 4 with 188HP. Plus, these new 4's aren't the noisy and crude engines of 30-50 years ago.
Same with buses. The last coach I was on was a 2020 J4500 with the CUMMINS. At idle speed it hardly had any vibration compared to those earlier CUMMINS and DETROIT S60's from back in the 1990's.
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Cummins has a special build ISX 12 for bus use and they are smooth and quite,my ISX 15 is not quite or smooth on idle,the old 8v71 or 8v92 Detroit are really smooth on idle
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My pre electronic Cummins C 8.3 is rated at 320 horse,, about the same as a 71 or 6V92,, but has over 900 foot pounds of torque!! Put this with a 6 speed allison and the match is great without the hassles of older or more modern combo's..>>>Dan (The side mounted radiator is cooled via a hydraulic fan motor that simplifies the install,, the hydraulic pump is gear driven on the engine and also serves the power steering.) ( A great upside is 10 miles per gallon.)
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do you know if your prevost is running a fan clutch or does it have a old school fan with no clutch?
No fan clutch, direct drive with a nine-blade Horton nylon cooling fan.
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Prevost with the 4 strokes have a fan clutch
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Except for increasing the power on a 8V-71, I wouldn't waste my time, or money at converting to a 8V-92TA. All 2 stroke Detroits are disappearing-along with the mechanics to work on them. This is one of the big reasons I converted my '85 Kenworth with Caterpillar 3406B (3406C mechanical is still being made).
The engines that I would convert too would be a Cummins ISM (still being made), Cummins X12 for a smog engine. A Caterpillar C12.
The Detroit Series 60, Caterpillar C15/C16/3406, Cummins X15 are all big block truck engines and are not necessary to move a bus down the road. Good Luck, TomC
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Utahclaimjumper-900lb/ft torque sounds like a lot of torque-granted it is 100lb/ft higher than the 8V-71N. But consider that the high end motorhomes now with Cummins X15 are putting out 1950lb/ft torque-no comparison in performance. Good Luck, TomC
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Tom,, My friend has a new 6.7 Cummins in his Ventena that comes in at 45K loaded , this engine is rated at 360 horse and makes very little more torque than my 8.3.. It moves that coach very well..>>>Dan ( It really isn't necessary to feed a monster all the time.)
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Friends of ours have a Newmar on the Spartan chassis with the B model 360 hp Cummins it is rated at 800 ft lbs of torque, it doesn't weigh close to 48,000 lbs and is a little on the weak side for a 37 ft.Hind sight he wishes for the L series Cummins for the $9600.00 extra cost now available in the 40ft
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You NEVER have enough horse power,,,but you CAN make due with what you have using common sense..>>>Dan
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You NEVER have enough horse power,,,but you CAN make due with what you have using common sense..>>>Dan
Yep plenty of old buses around with the old 4-71 Detroit you just don't see those on the Interstate highways and they are enjoying the scenery of the past before all the concrete, I am with that crowd since I am in no hurry from point A to B
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Yep we like the back roads and stay off the super slabs as much as we can. You seem to find more fun stuff on the back roads by accident. :^
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Yep we like the back roads and stay off the super slabs as much as we can. You seem to find more fun stuff on the back roads by accident. :^
I like old town squares,on trips to Texas we go all the back roads makes for a long driving time but about all the small towns in Texas will have free or low cost camping grounds,I disklike the long boring I 10,I 40 and I 20 route,I do come back home on the interstate sometimes lol I even like the back roads in CA,you see a lot of history and some nice places
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I remember buying my first truck in 1980. The big engines were Caterpillar 3408 at 450hp ($12,000) or Cummins KTA600 ($16,000). And the thing was with mechanically injected engines, the bigger you went the worse the fuel mileage. I got 4.8 mpg with my 8V-92TA. Those other engines would be in the low 4's.
Now horsepower and size of engine really doesn't matter with electronic common rail fuel injection-it is more the way you drive. So when considering an engine with common rail fuel injection, get the biggest most powerful version you can get. Good Luck, TomC
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Bigger is also heavier to haul around ,,and more expensive,, how much do you really need.?? >>>Dan
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Low power is very stressfull, especially on B roads in the summer with heavy traffic and limited passing opportunities. Takes all the fun out of a journey.
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I said nothing about low power,, only about needed power. It''s no more stressful to travel in 4th gear for a few miles of grade than to travel in 6th gear under the same conditions.. In my experience climbing in the right lanes are less stressful than competing with the jerks in the left lane going the speed limit or more and riding your @$# trying to get around you .>>>Dan
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We need to be mindful of the motorists behind, we share the road, of course, BUT...
We will go at whatever speed we are capable of, or choose to do, and those behind can deal with their misconceptions.
As you approach 20% below the posted limit, throw on the hazards, and carry on.
If the followers can't handle that the big old bus is slow climbing, that is totally not your problem.
If going slow makes stress, that's not good.
Happy coaching!
Buswarrior
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@bw - first time a number where turtleness triggers the flitp of the hazards. For me it just seems natural at some point when in the slow lane and going slow it makes sense to turn them on. LOL
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Older buses going up the grade from Phoenix to Flagstaff do cause a lot of problems on I 17,I saw a MCI pull over on the grade to cool off and the poor guy couldn't get going from the stop because of the grade,black smoke and the smell of a clutch slipping was the best he could do before the wrecker came
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Older buses going up the grade from Phoenix to Flagstaff do cause a lot of problems on I 17,I saw a MCI pull over on the grade to cool off and the poor guy couldn't get going from the stop because of the grade,black smoke and the smell of a clutch slipping was the best he could do before the wrecker came,he had a mile of traffic backed up and all were pissed off big time
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4 speed manuals were fine when the buses were Greyhound and only running on their specific routes. But motorhomers are adventureous and the 4 speed is just not enough. Even though your fuel mileage takes a hit, the first thing I'd do is to switch to an Allison automatic or a 10 spd Ultrashift. Good Luck, TomC
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Tom makes a great point. All our buses that were purchased for revenue were built to the standard necessary to run the designated carrier routes. Thus, we know how we struggle on some roads that probably were not in the schedules. That said, maybe back in the day, chugging up a grade at 15mph belching smoke was better than riding a horse or walking. LOL
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Extra gears can help, but ultimately the percent of grade and whether engine is in its power band dictates max speed on a grade. They will help on rolling terrain though.
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" Speed is never a priority when climbing,,, getting to the top with everything running well is."..>>>Dan
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What UCJ said... :^
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I was planning on converting a bus & upgrading to a 450hp 8v92 - I already had the engine & radiator out of a Peterbilt. The Peterbilt radiator was smaller than the 8v71 bus radiator.
I found an ~25 year old factory built motorhome for less $$ than I had already budgeted (& not yet spent ) for my bus conversion. This worked well for me as everything was well executed in the build & the 475hp 8v92 & allison 4 spd work very well together.
I like the simple & redundant systems built in. My Newell is so much nicer than anything I could have built . . .
All that said to say - don't over look options that may enable you to reach a better goal.
Doing the work myself is always satisfying - However, enjoying it NOW is quite nice too.
My wife found the Newell we bought - I had wrongly assumed they were out of my price range. . . .
Hard to beat the sound of Jake brakes on a 2 stroke !!!
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Kyle, I too, love my Newell! Been renovating the interior. I was in the market for a bus conversion myself when this one happen to tick all the correct boxes except paint color.
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tick all the correct boxes except paint color.
The Rolling Stones said it best
"You can't always get what you want
But if you try sometime you'll find
You get what you need"
:^ 8)