hi i have both engines for my mc5a, what are some of your pros and cons , i dont care much about the differance in fuel, i just want the best performance, thanks oh ya the 871 is a 1980 model,and the 692 is a 1978 model if that matters
All things being equal, the 6V92TA wins hands down over an 8V71N. Now it the 8V71 has a turbo....that's going to equalize things. If no turbo, no comparison.
Go with the 6V92TA. It's a fundamentally better engine design.
I'd go with a later 6V92TA. HP could range into 350 HP. Also common in 270, 300, and 330.
Pay attention. There were 6V53s out there too. You DoN'T want one of those.
The early 6V92s had less than the best blocks castings. Find an engine from an 80 model or later. Avoid the 'Alpine green' blocks and look for a silver...or purple! Purple was an in-house NJT rebuild. The NJT folk did good work.
JR
Here's the difference- the 8V-71 is 568cu in. The 6V-92TA is 552cu in-so that 16 cu in isn't going to make a squat of difference with the two set up the same. For instance a 6V-92 with 90 injectors will be out performed by a 8V-71 with 70 injectors (both turbocharged).
Personally-if you're going to keep the manual transmission, keep with the 8V-71-it is more reliable and you don't have to worry about the cylinder liners leaking since the 71 series has dry liners.
If you're going to install a HT740, then go with the 6V-92TA (because of length space on a 5). With the up graded injectors, you can get with 9G00 (100) injectors 370hp and 1050lb/ft torque. But with the 8V-71 with 90 injectors you can get 450hp and 1350lb/ft torque. I have a turbocharged and air to air intercooled 8V-71 in my transit with sedate 9G75 injectors for 375hp and 1125lb/ft torque and love the performance. I get 5-6.5 mpg. Good Luck, TomC
Keep in mind that we're talking about an MC5. I'll wager that trying to cool a big humpin' engine in an MC5 is going to end up costing more (and require more engineering) than the engine swap. I won't wager much....just a little bit. :)
HP equals heat. Heat dissapation costs big $$$$$$$$$$$ ;)
Another thingy is that there are very few 8V71Ts around. Probably have to build one from an "N" model....$$$$$$$$$$
Tom, for a reference point, advise "MC" how much you paid to have your 8V71 turbo'ed? ::)
If looking for a high horsepower engine, an 8V92TA also has similar dimensions compared to an 8V71.
Couldn't cool it either though. Not without re-engineering the coach cooling system.
Changing out to a 6V92TA will require cooling improvements too...just not as radical.
What's in your wallet?
JR
The turbo job including the enlarged radiator, custom made air to air intercooler, bigger muffler and air cleaner, then on the engine itself, bigger injectors, bypass blower valve, custom exhaust to facilitate the turbo, new oil pump- $12,000.00. Compare that to an engine swap, and I think you'll see it isn't that bad. Throw in a complete over haul and you'll still be under $20,000. I priced out changing my engine/transmission to a Detroit series 50 with the HD4060-changing the bus from a V drive to a straight drive since my model of bus came either way, and I was looking at around $35,000. Even with the increase of fuel mileage from 5-6.5 to 8-10, I couldn't justify it, so the turboing job was next best. Good Luck, TomC
Performance wise, they are about dead even. Otherwise, each type has its advantages and disadvantages. I think the V8 sounds better than the V6, but that is an abstract. Good luck. :) :) :)
thanks for the info, what engine will climb the mountains better?
I have put several hundred miles in a GM 4106 with both motors. I own one with an 8V71 and my fathers has the 6V92. Hands down, I like the 6V92 better in all aspects. I also like the sound of the six better than the eight but that is personal preference (My father's has a smaller muffler so it sounds sweet, and the sound of the turbo spooling up is just plain cool). However, the difference could be in the health of the engines but I don't have another 8V71 to compare mine. I also think the turbo might have a lot to do with the performance especially when climbing hills and the lack of black smoke. I have N70s and my father has 90s or 95s I don't quite remember. I used to be a die-hard traditionalist for the 8v71, but not anymore. I might add that in addition to out performing mine, he gets better fuel mileage.
Good question as to which mill would climb hills better. My best guess here is, that in a Bus Conversion, the 6V92 would have a slight advantage. Too many different variables, like trannys, gearing, engine settings, etc.. :) :) :)
Quote from: mccarlk on August 05, 2008, 02:57:33 PM
thanks for the info, what engine will climb the mountains better?
At higher elevations, definately the 6V92 compared to a non turbo 8V71 Jack
FWIW the torque on a 6v92 is 957 lbs and on a 8v71N 318 hp it is 818 lbs but the 6v92 has a faster torque rise and with a 8v71 TA set at 350 hp it will be 1038 lbs
It seems from most of the posts, the raw engines are going to be pretty similar. It all depends on turbos, injectors, and cooling. If that is the case, what are the specs on the two engines you have? As I understand the posting, you already have the engines and were not necessarily looking to buy another. Further, if you are looking to use the engines as they are without putting much work into them, you might want to get them tested to see which comes out on top.
the 692 has the 90 injectors, and the 871 has the 65s, as for cooling i dont mind upgrading to have a turbo motor, seems that it will climb the hills better, the coach is only 35 ft so im hoping for fairly good performance, i will be rebuiding what ever engine i use, that way i will be starting fresh, the trans is already rebuilt,
Well. If you're going to rebuild your next engine anyway, and don't mind spending a few thousands of bucks, the least expensive way would be to turbo your 8V71N. The injectors pose no issues...replace them with whatever you want. The end result would be good.
But, upgrading the cooling system will be necessary.
An uphill race between an 8V71N v 6V92TA would favor the the 6V92TA considerably.
However, a turbo'ed 8V71 will easily compete against a 6V92TA.
Still, 6V92TAs are everywhere...and not too expensive. An 8V71T will have to be created. They are rare. The military uses them...and you may be able to find a new or reman surplus military engine. They turn up on the 'net often.
At altitudes, a turbo engine is a definite plus.
Have you considered an 8V92TA? If you don't mind upgrading the cooling system, an 8V92TA would be a huge improvement in performance and durability. Build yourself a veritable "sports" bus. A relaxed 400 HP.
An 8V92TA would be almost a bolt-in as far as dimensions go. Exhaust plumbing mods will be necessary.
I'm not familiar with the engine room of an MC5, but you may wish to verify that you have overhead space for the blower mounted turbo on these engines? They are pretty tall.
Good luck! JR
I would choose a turbo engine, for mountain performance. If you want an automatic, the 740 is strong and can fit behind a 6V92 in an MCI 5. You must go to a small, weaker Allison transmission 64X behind an 8V71 in an MCI 5.
Ed Roelle
Flint, MI
If I had the MC5, my hands down choice would be the 6V-92TA with automatic. Recently, Detroit built up a DDEC 6V-92TA for Jay Leno's bus at 435hp and 1350lb/ft torque (course that will only last maybe 200,000 miles) with the World B500. Now that would make a real hot rod out of a MC5-but of course they have a giant radiator on it also-maybe could fit the 8V-92TA radiators? Good Luck, TomC
Interesting that the overheat problems come up so often on the MCI *V92 upgrades.
Has anyone ever considered changing from the squirrel cage/side radiator configuration to the more modern single radiator across the back like the late 102C's and D's and E's use?
I've seen several of the D's and DL's with the high horse power 92's using the rear radiator configuration that seemed to work much better than those tiny side radiators.
I know someone here is going to bring the cost into this conversion, but it seems to me that you could make a couple of the side to rear conversions for what it would cost to do all the other bandaid fixes that are being done.
This was jut a thought from my befuddled mind.
Dallas
Dallas, that is interesting there was a MCI 9 at Southern Oregon Diesel that had 1 large radiator across the back with 2 fans driven by belts 1 from the engine and 2 across to the fans he told me it came from a school bus and he had a 475 hp 8v92 with no heating problems.And I also saw a 9 with a 4x4 radiator mounted on the right side he also had a 8v92 with no problems so he said
I don't think there is room enough in the MC5 to put a turbo with a 8v71. You could put the turbo behind a 6v92 like the Eagle buses. If you don't put too much power with a 6v92T you could still use the 640 allison trans. Some of the prople that tried to change a 8v71n to a tubro had lots of problems.
Jack
Well Blue Goose-I haven't had any problems with my 8V-71N converted to a turbo. Just had to enlarge the radiator, muffler, air cleaner, etc. It now runs very well with virtually no smoke coming out of the exhaust stack on a major hill pull. I am quite pleased with it and firmly believe it is the best route to take if you want more power, and especially the advantages of turbocharging for altitude compensation. Good Luck, TomC
Tom C
I didn't say there were problems, just questioned the room for the turbo. There is just enough room for the allison 640 and 8v71. Where did you put the turbo and the extra parts for the turbo?
Jack
If you don't have room for a front remote mount turbo like the Eagle you can always side mount it, and it will be closer to the charge air cooler The problem you will have is if the 8V71 is built right the 640 won't handle the HP and TQ A properly built 8V71 will run along side an 8V92 and run quieter smother and use just a little less fuel. You might be down 25-30 ft lbs tq from the 92 but you wont miss it.
Don
Quote from: Dallas on August 06, 2008, 08:30:30 AM
Interesting that the overheat problems come up so often on the MCI *V92 upgrades.
Has anyone ever considered changing from the squirrel cage/side radiator configuration to the more modern single radiator across the back like the late 102C's and D's and E's use?
I've seen several of the D's and DL's with the high horse power 92's using the rear radiator configuration that seemed to work much better than those tiny side radiators.
I know someone here is going to bring the cost into this conversion, but it seems to me that you could make a couple of the side to rear conversions for what it would cost to do all the other bandaid fixes that are being done.
This was jut a thought from my befuddled mind.
Dallas
Dallas so funny you should mention that! I been think'n bout this swap lately myself! Hmmm could be something here! Now don't all you guys with deep pockets go buy'n up all the used D style radiators there are now! ;D BK ;D
PS it would go right nicely withan upgrade to a "D" rear cap!
Quote from: Don Fairchild on August 07, 2008, 03:03:58 PM
If you don't have room for a front remote mount turbo like the Eagle you can always side mount it, and it will be closer to the charge air cooler The problem you will have is if the 8V71 is built right the 640 won't handle the HP and TQ A properly built 8V71 will run along side an 8V92 and run quieter smother and use just a little less fuel. You might be down 25-30 ft lbs tq from the 92 but you wont miss it.
Don
Quieter? what ya say? I can't hear ya over my big honk'n hot rod 8V92! LOL! ;D BK ;D
On my 8V-71 with V drive the turbo is mounted above the right (upper) valve cover with a rather long pipe coming around the front of the engine for the left head exhaust pipe. With the long run, it takes about a mile for the turbo to warm up, but once warm, it does a great job. I used a early Series 60 turbo with waste gate to restrict the turbo pressure to about 15psi.
You can basically mount a turbo where ever it is convenient. Course it is best to mount it as close to the exhaust manifold as possible. There is nothing wrong with using two 4-71 turbos-one mounted on each exhaust manifold then T'eed together at the blower. This is done on the hotter running engines. For instance, some hot rodders with 12V-71's use two 8V-71 turbos to get big boost-course you also need big injectors-along with a big wallet for all that fuel burned. Good Luck, TomC
Quote from: Dallas on August 06, 2008, 08:30:30 AM
I know someone here is going to bring the cost into this conversion, but it seems to me that you could make a couple of the side to rear conversions for what it would cost to do all the other bandaid fixes that are being done.
Dallas
Dallas, what about the cost?!! ;D
Sorry, couldn't resist! JR ;)
Don ,when you said a properly built 8/71 ,what do you mean, the 871 i have is rated for 318hp, a far cry from 475 out of a 892, what can i do to bump up the hp, also could i not run a truck style rad where the rear engine doors are with some heavy duty electric fans to help any heating problems?, thanks again guys for all the input
McCarlk -
FYI, a little history:
MC-5 A & B models all came from the factory with 8V71s mated to Spicer 8844 four-speed manual gearboxes, no automatics were available. (Yours has to be an after-market retrofit.)
MC-5C models were available with two different powertrains: Either the 8V71 mated to the four-speed stick, or a 6V71 / HT-740 combination. The 8V71/HT740 combination found in other MCI models is too long to fit in the 5s, hence the 6V71/HT740 option.
Now, the 6V92TA is, for all practical purposes, the same size as the 6V71, therefore:
The best "bang-for-the-buck" in your MC-5a would be a 6V92TA bolted to an HT-740 Allison. 8)
Have the six tuned for 350 hp (usually just an injector change to 9G90s), and you'll have a very sweet little hot rod. You will have to side-mount the turbo, however, as the blower compartment floor is too close to the top of the engine on a 5.
Make sure you install the larger radiator cores and squirrel cages from the MC-9s with 8V92s, and you should have plenty of cooling available.
Is it worth the cost? Who knows, it's a toy and a hobby! :D
FWIW & HTH. . .
;)
We drove lots of MC5s in the '70s for Brewster's (Banff, AB). The As and Bs with the 8V71 and 4 speed manuals were great. Lots of power compared to the 7s with the same powertrains: better power to weight ratio. Then in 1978, I remember picking up brand new 5Cs in Winnipeg with the 6V71/auto trans combo: real dogs, no power, disapointing!
If I were you, I'd go for the 6V92 with a turbo and auto. There might be a way to mount the turbo on the side like I did on my 4-71, if you have the space there. You have to get creative with the intake and exhaust plumbing.
Those MC5s are the greatest bus.
JC
hi rj, my bus was set up with a 871 and the 600 series auto, im just afraid to put the 871 back in because almost everybody on the board always has problems with the power on the 871, ifi was to build my engine with the turbo pistons could i run a turbo on it? i could remote mount a turbo?
You can run either a single or dual turbos mounted anywhere that is convenient-closer to the engine the better. Rebuild your 8V-71 with turbo pistons and run a mild 65-75 injector for maximum engine life and fuel mileage. Good Luck, TomC
What about cooling down with water injection? Bill T.
hi tom, do you know what kind of hp i will have with a 75 injector,and a turbo, will i have to limit the amount of boost?
I have 9G75 injectors in my 8V-71 and had it dynoed. It came out at 375hp and 1125lb/ft torque with the air to air intercooler. Without any kind of intercooler or aftercooler look for more like 350hp and 950lb/ft torque with the same injectors. Good Luck, TomC
Tom , can i bump the hp to around 400, with the 1100 ft torgue? what would i need to do?
Detroit's last version of the 8V-71TA with 80 injectors was 400hp with 1200lb/ft torque. You would need to rebuild your present engine up to a turbo spec engine, then you could just get the exact specs of this engine for the injectors (7G80), turbo pistons (17:1 compression verses the 18.7:1 you have now), bypass blower valve, fuel modulator (keeps the injectors from opening until you have turbo boost-otherwise you get a big black smoke cloud each time you push on the go pedal), increase your radiator, muffler and air cleaner, and install an air to air intercooler. Sounds like alot, but it still is the cheapest and easiest way to go to get a turbo engine into your bus. As stated before, you could run one turbo or two smaller, it doesn't matter. If you have room on the sides of the engine, maybe two smaller 4-71 turbos would be the way to go. Good Luck, TomC
Quote from: TomC
Detroit's last version of the 8V-71TA with 80 injectors was 400hp with 1200lb/ft torque. You would need to rebuild your present engine up to a turbo spec engine, then you could just get the exact specs of this engine for the injectors (7G80), turbo pistons (17:1 compression verses the 18.7:1 you have now), bypass blower valve, fuel modulator (keeps the injectors from opening until you have turbo boost-otherwise you get a big black smoke cloud each time you push on the go pedal), increase your radiator, muffler and air cleaner, and install an air to air intercooler. Sounds like alot, but it still is the cheapest and easiest way to go to get a turbo engine into your bus. As stated before, you could run one turbo or two smaller, it doesn't matter. If you have room on the sides of the engine, maybe two smaller 4-71 turbos would be the way to go. Good Luck, TomC
mccarlk you should give Don Fairchild a call he is who built Tom's current set up and in my honest opinion (which will buy a gallon of fuel if ya add $5 to it!) the guru of hot rod 8V71's. (or any 2 stroke for that matter!) And the twin turbo set up would look way cool too!
;D BK ;D
Quote from: mccarlk on August 09, 2008, 09:42:06 AM
Tom, can i bump the hp to around 400, with the 1100 ft torgue? what would i need to do?
McCarlk -There is nothing wrong with the stock power output of the 8V71. It was the industry's reliable work-horse for over 20 years. Sure they were slow in the mountains, but reality-check time: we're driving a BUS here, for goodness sake - not a BMW!
If you hot-rod your 8V71 and keep the same transmission, be prepared. That gearbox will NOT stand up to the high-hp V-8, as it's a medium-duty model. Putting 1100 ft/lbs of torque into it could very easily leave you stranded along the roadside with a blown transmission.
The HT-740 will take the high HP & torque of a hot-rod motor, but will NOT fit with the V-8 in your 5A.
As I said before:
"The best "bang-for-the-buck" in your MC-5a would be a 6V92TA bolted to an HT-740 Allison."Or simply reinstall the stock 8V71 with that 600 series Allison, sit back and enjoy a reliable and dependable ride - what's the hurry, anyway?
FWIW & HTH. . .
;)
PS: Another thought: Putting in a high hp motor will also increase your fuel cost
all the time, not just when you're climbing Rocky Top. Gotta pay to play!
the engine i have is from a 80 5c with a manual, will the bell housing on the engine accept the auto?
It should-or you can change the bell housing to fit the automatic. Good Luck, TomC
If you are going to use the 644 with that bellhousing you need a drop down adapater plus a 15/16 spacer ring and if you can find a sae 2 bellhousing for a MCI which I doubt you still would need the spacer
where can i find the adapter i need? the original engine is long gone
Check any large truck salvage yard.
Jack
good morning guys, great news for me, i went out to check the trans and it has the adapter plate still on it, this bus is great, best deal i have ever got, there must be thousands apon thousands, was done by someone very in to detail, oak, corion every where, before the engine was blown up the people just put new rads, new alcoas and tires, batterys, air bags , brakes, new steering box, velvac mirrors, comfort air mattress with the heaters, list gos on , holy crap im so excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Quote from: mccarlk on August 11, 2008, 05:07:49 AM
good morning guys, great news for me, i went out to check the trans and it has the adapter plate still on it, this bus is great, best deal i have ever got, there must be thousands apon thousands, was done by someone very in to detail, oak, corion every where, before the engine was blown up the people just put new rads, new alcoas and tires, batterys, air bags , brakes, new steering box, velvac mirrors, comfort air mattress with the heaters, list gos on , holy crap im so excited!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
KWEL! It sounds as though you've found the proverbial "needle in the hay stack!!" While not usually the case it is great to hear of it when someone actually hits a good deal! It musta been the straw that broke the previous owners heart & wallet when the blew! Hang in there and enjoy it! But keep in mind that theses things are expensive toys, and from time to time ya gotta spend some to keep 'm happy! :D BK ;D
hey busted kinuckle, yes the engine blew and the couple divorsed, and my guy bought it cheap, thanks for the words of encoragement, this is number three for me and ive learned alot during the way ,