| Author | Message | ||
| Charlie Sizemore (Goldenhawk)
Registered Member Username: Goldenhawk Post Number: 1 Registered: 11-2009 Posted From: 32.179.178.20 Rating: N/A |
I don't own a bus but will need one within the next few months. I ran across a nice looking GMC 4905 ('76). Recently capped and painted. Looks like a first-rate job. Owner says less than 100k miles on rebuild according to church he bought it from. Has a 8V71 318 Detroit engine. Runs smooth; automatic. Not a conversion. So the question: Why is everyone I speak with scared of this engine? Is is dramatically different than, say, a 6V92? Seems as if the "V" is an issue with the 71 but not the 92. I probably could get this bus for around $7,500. although they're asking 10k. Then there's a MCI 8 conversion with the 6V92 turbo with 70k on rebuilt '92 engine from a Peterbilt- or so I'm told. I could get this for less than 16K, I think. I guess the bottom line is this: the buffalos look nice (moreso than MCIs to my eye) and best I can tell they seem to hold their value pretty well. It appears that I can get a newer MCI for the cost of a buffalo. Is there a reason that an 8V71 in an MCI is more to be desired than the same engine in the GMC? Seems that's what I am gathering although I could be mistaken here. I'm confused and obviously a neophyte. I'd appreciate any comments to the extent that any of you are able to interpret this comment or question or whatever it is. Thanks. | ||
| Ednj (Ednj)
Registered Member Username: Ednj Post Number: 265 Registered: 3-2003 Posted From: 67.82.205.78  Rating: N/A |
I like the 71 series they can handle idling better than the 92 series. The engine in the GMC runs in the opposite direction as the MCI and most trucks. Church owned buses are notorious for poor maintenance. It’s getting a little harder to find parts for the GMC’s but MCI is still making buses and they got it right. | ||
| Bob MacIsaac (Wildbob24)
Registered Member Username: Wildbob24 Post Number: 60 Registered: 5-2007 Posted From: 68.155.150.83  Rating: |
Charlie, Some of the old hands here will chime in shortly, but I'll start the discussion. I don't know why any one would be "afraid" of the 8V71. I think it's one of the best engines DD made. The difference between an 8V71 in a GM and one in an MCI is they turn in opposite directions. Other than that it's the same engine. The GM drivetrain is a V drive configuration with a LH engine, while the MCI's is a T drive configuration with a RH engine. Personally, I prefer the GMs, not only for the look, but the engine and transmission are much more accessible for maintenance and repair. That said, the T drive is the standard configuration these days and the components are easier to find. You can, for instance, put a truck engine in an MCI, with minor modification. Not really an option with a GM Bob | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 669 Registered: 3-2007 Posted From: 71.53.153.91  Rating: N/A |
Couldn't have said it better if I tried Bob, I concure 100%. I love the GMC's gomer | ||
| Peter E (Sdibaja)
Registered Member Username: Sdibaja Post Number: 322 Registered: 5-2002 Posted From: 201.143.51.205  Rating: N/A |
I would assume "rebuild" on a "church bus" is most likely just a fresh box of band aids. The stereo-type is well earned... assume the worst on that unless they can clearly document way better. The 8v71 with the V drive in the GM are known to be bullet proof but sometimes leakers and usually not gonna make any MPG records. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1752 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
GMC are nice because so many of the parts are interchangeable with older models. All the windshields are the same; the engines and trannys are basically the same from 4106 on. Right hand Detroit 8V-71's can easily be converted to left hand rotation for use in the GM's. You don't have the rust issues that that Eagles, Flxibles, and MCI's of that period have. GMC's were designed for convenient maintenance compared to the other brands. GMC's had lots of storage and better steering till probably the MC-9's came out. Every one has their favorite brand, but the GMC's don't have to take a back seat to any of the other ones. People like the 6V92's because they are available in large quantities currently, because most of the city busses that are starting being scrapped today had mostly this engine. They can put out 350 horse, are mostly turboed and can easily be used in place of the 8-71. Since they make that much power with a 6 cylinder engine compared to the 8-71 which were mostly non turboed and rated around 250 horsepower,they were cheaper to rebuild as far as parts costs. There is nothing wrong with the eight though, just economics if you need to rebuild. | ||
| J.L.Vickers (Roadrunnertex)
Registered Member Username: Roadrunnertex Post Number: 64 Registered: 10-2006 Posted From: 74.5.97.188 Rating: N/A |
Well I am going to be pro GM 4905 with this post. As I own a 1974 P8M4905A The 1976 GMC P8M4905A has a Sheppard power steering system that was standard on the P8M4905A's of this vintage. MC-8 has power assist ram style steering. The GMC intercity coaches of that era were far ahead of MCI coaches in many areas.Steering and ease of maintenance on the engines,power steering pump,alternator and air compressor replacement. The transmission if it's a automatic or a standard shift can be changed with a lot less effort than on a MCI. Look at the MC-8 and inspect it close for rust in the main structure and the rear baggage bin bulkhead in front of the rear drive axle area. I know where there is a MC-8 that looked very nice until the new owner removed the interior and all of the frame work on both sides of the coach was gone due to rust. Needless to say it's in the scrap yard now. Look at these old coaches twice and make sure you understand what you are getting before the money changes hands. jlv | ||
| Charlie Sizemore (Goldenhawk)
Registered Member Username: Goldenhawk Post Number: 2 Registered: 11-2009 Posted From: 166.214.197.255 Rating: N/A |
Appreciate the help. And please don't infer that I'm not open to any additional ideas or suggestions. To this end I also spend a fair amount of time reading older posts - without which I doubt I'd have the acumen to even cobble together my question, muddled as it was. | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 144 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
I wouldn't be afraid of either 2 stroke engines. There are thousands still in service. I like the 71 series better since it has dry cylinder liners, unlike the wet cylinder liners of the 92 series that can leak over time. Other then that, if you're going to change the engine, use a 4 stroke engine instead, since the 2 strokers are getting harder to find quality mechanics to work on them. Good Luck, TomC | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 925 Registered: 8-2006 Posted From: 99.39.13.151 Rating: N/A |
As everyone has mentioned above, church buses are notoriously neglected, for obvious budgetary reasons. The other thing to think about, is how long it would take to get a hundred thou on a church bus? In other words, the overhaul is OLD! The GM angle drive essentially limits transmission choices to the 4-speed non-synchronized stick, or the 730 Allison 3-speed automatic. The rest of the highway buses are T-drive, and most can use 4 or 5 speed Allisons, and most of the other standard truck transmissions. JLV is right, look closely before you buy. I would strongly suggest you look at, and drive several coaches by all of the mfrs. before you decide. Welcome, and good luck! G | ||
| Ken Barnett (Dieselbusparts)
Registered Member Username: Dieselbusparts Post Number: 16 Registered: 7-2009 Posted From: 76.26.111.30 Rating: N/A |
The v71's and v92's are very similar and have many interchangeable parts the biggest difference is the cylinders, the v71's use a direct heat transfer cylinder while the v92 use more reliable water jackets on each cylinder providing a cooler running engine, either way they are both designed to be worked on, and will give millions of miles and rebuild quick, parts are always going to be available as long as there is a demand! | ||
| Jim Shepherd (Rv_safetyman)
Registered Member Username: Rv_safetyman Post Number: 289 Registered: 1-2004 Posted From: 72.171.0.144 Rating: N/A |
It was touched on in one of the earlier posts, but the big difference is that the 6V92 is a turbo engine, while the 8V71 is not. The turbo will make quite a difference at altitude. An 8V71 in Colorado is pretty puny. Having said that, there are folks on this board who have added a turbo and charge air cooler and that makes the old engine come to life. Jim | ||
| Donald P H (Eagle19952)
Registered Member Username: Eagle19952 Post Number: 11 Registered: 11-2007 Posted From: 75.251.31.156 Rating: N/A |
I have the 8v71 Detroit. one thing kind of off the wall a bit to consider....the heat that the turbo throws off can make sleeping a whole lot more miserable after a long day....these engines can take a long time to cool down on a 80-90 degree nite and sit about 8 inches under your rack. And more HP uses more fuel,slow down and see the sights. my .02 cents. Just a thought. | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 145 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
Donald- believe it or not, whether you go up a hill at 20mph or up the hill at 40mph, you are ultimately using the same amount of fuel to climb that hill. Personally, I would like to get over the hill faster, so my 8V-71 that is turbocharged with air to air intercooler is rated at (by dyno) at 375hp and 1125lb/ft torque-which is more then the 350hp and 1050lb/ft of the 6V-92TA. Detroits last offering of the 8V-71TA was rated at 400hp with 1200lb/ft torque with 80 injectors. After turboing my bus, I still get 5-6mpg, but with superior performance. So actually, it is much more fuel efficient now. Good Luck, TomC |
