A bus I am considering is a 4107 with a 8V71T motor. I need to get more details about this specific motor and the history of how it came to be in this coach. Research indicates there are various configurations that affect the power rating. See below
Common sense tells me if the turbo came with the coach from the factory than the supporting systems are engineered to meet the output of the motor. If it is a repower it might have cooling problems if the radiator was not upgraded. The TA indicates the block may be slightly tougher to handle the extra power. If the motor was a standard 8v71N with the turbo added later than it may not be durable as it should be. What do I need to ask to extract the specifics of this motor/coach combo? thanks
8v71T 308hp with n65 injectors 865 lbs torque
335hp " n70 " 920 "
350hp " n75 " 965 "
8v71TA 370hp with 7c75 injectors 1064 lbs torque
8v71TT 305hp " n75 " 1038 "
8V71TA 400hp with 7G80 injectors 1200lb/ft torque
8V71T? 375hp with 9G75 injectors 1125lb/ft torque
If you read the serial number off the engine, it will indicate it's original configuration. Unless you were interested in having the after cooler in the cylinder block, I wouldn't worry about block strength. Anything over 65 injectors is going to make overheating a issue you'll have to be careful of on long hills and really hot weather, unless the radiator has been upgraded/ mister system added. Pull the rear valve cover to red the injector tag number. Easy to remove; two knobs or bolts. If I was considering this coach, I'd pull an oil sample on it and have it checked, unless someone just changed it. I'd be interested in pictures of the engine layout with respect to turbo mounting and associated exhaust/intake plumbing, as I have been considering turboing mine.
You can tell if it is aftercooled (TA spec) by looking to see if there is a coolant hose coming out of the middle of the valley between the cylinder heads (just behind the fuel pump) to the right hand (facing out on a transverse engine) thermostat housing. The TA cooler is on the floor of the blower valley, roof of the airbox, the blower forces the air through cooler. As far as I know the 4107 was over in 1969, and wouldn't have had a turbo engine stock (8V-71T came out in the 1970's, I seem to recall), so what you have is almost certainly a re-fit. If it's a refit then someone could have turbo'd the stock engine, or fitted a turbo engine. The main difference is the compression ratio, the turbo engine has a 17:1 compression ratio while the N engine is 18.7:1. Someone could have turbo'd an Natural engine and left the compression at 18.7, turbo'd an N engine core block and changed the pistons, etc. It being a left hand rotation, I don't know if any factory turbo automotive engines were ever produced, but there are lots of RHR turbo engines around. a 4107 with a 350 HP turbo engine would be a real sports-car!
Just below the serial number of the engine (back of the block, towards the rear, below the exhaust manifold, so you can't see it easily on a transverse engine) is an engine type code. Yours will be a 708X-4YZZ. The 7 means V71 series, the 08 means 8 cylinders, the X is a vehicle type designation, the 4 means left hand rotation, the Y is a design variation. In this position, 0 means Natural, 1 means 2 valves, 2 means 4 valves, 3 means turbo, 4 means turbo aftercooled, 5 means custom spec., 6,7 and 9 mean California or constant HP spec. ZZ is a specific model number that might mean something or not. There are some detail differences between the N block and a TA block (mostly the hole for the coolant hose to come out of the block to the thermostat housing) but I'm not aware of any strength differences. Lots of non-TA engines were built with TA blocks and the hole for the hose just blocked off. Mine is like that (I have a factory turbo 8V71 NATO engine)
Brian
Thanks busnut as always. I'll report back what's up.
Sent from my SM-N910V using Tapatalk
If it is a ta
block without intercooler installed, it will have a 2 inch (approx) hole plug in the valley between the heads. Personally, I wouldn't want the intercooler in the block...expensive, another place for potential coolant leaks, and that heat from compressor air from turbo just adds more heat to cooling system. Add engine oil cooler and, if equipped, auto trans oil cooler, you re asking a lot for the radiator that is in that coach.
If you purchase this coach, definitely add a good mister system if it doesn't already have one. They are relatively inexpensive to make.
or it could be a low boost turbo contraption with the NA pistons still there...some awful abortions have been accomplished... ???
the serial# config might reveal the truth...
and it might not...
Your torque and hp numbers mean very little if you don't know how the engine is configured injectors alone are just another piece in the puzzle
I converted my 8V-71N to a turbo. Don Fairchild first looked at the piston rings and determined they were the tight fit rings-as compared to the looser rings that truck engines run. We kept the 18.7 to 1 pistons that were two piece (only difference between turbo and NA two piece pistons is the deck height). I added an air to air intercooler in front of the radiator (luckily had the room). But also had to increase radiator and also add misters. Increased air cleaner from 6" to 7" hose, added auxiliary transmission cooler with thermostatically controlled 12v fan, changed stuffed up muffler to turbo muffler, added by pass valve to blower, added fuel modulator. Was extensive, not cheap, but the performance is truly different. My fuel mileage is the same-mainly because we didn't change the cylinder liners or cam timing. But comparing the N65 injectors at 300hp @ 800lb/ft torque to the now 7G75 injectors at 375hp @ 1125lb/ft torque, you can see the difference in hill climbing with the torque increase. Good Luck, TomC
Thanks Tom, I knew you'd comment. Don F and you reviewed made the modifications to do this upgrade properly, ensuring long term reliability. It seems unlikely the same care was done with the upgrade on one bus under review.
Update: After speaking to the previous owner who knew more about this specific coach, it seems there is no verifiable documentation on the motor, period. It is a turbo but it is a repower, so the related systems are not engineered and designed for the higher power motor except a larger radiator. He stated the bus does well going up hill and you really need to watch the temps.
The pro on this one is it can trade hands at a price on the low end of the market value. But the discount is reflected in the risks on this one. Before I nix it for good, I'll touch base with Fairchild to see if there are other checks to assess the motor condition, other than it don't smoke and it don't clink or clank. :)
New twist to thread. Variations on the 8v71N using different injectors.
Injector size is directly proportional to the horsepower and torque the engine produces.
Researching how much one can improve performance from natural 8v71 using different injectors.
What does the busnuts say?
N55- 260hp and 680lb/ft
N60- 280hp and 740lb/ft
N65- 304hp and 800lb/ft
N70- 320hp (or 318hp if you prefer) and 860lb/ft
7G65 - Uses a different metering system, more accurate delivery, atomizes the fuel better,has better spray pattern,more adjustable ability and a higher pop pressure makes for cleaner burning better injector than the N series
A timing
N65 - Involves pulling the rear cover off (removing the trans from the engine).
N70 - Increase to 318hp and 860lb/ft torque.
You can use 7E65 injectors without A timing a 8v71N/A, 304hp with 818 ft lbs of torque @2100 rpm.A timing a bus engine is a waste of both time and money unless you have a 10 speed Roadranger transmission IMO
The 4107 was still produced in 1975.>>>Dan
Quote from: Utahclaimjumper on June 02, 2017, 05:26:51 PM
The 4107 was still produced in 1975.>>>Dan
Dan,
According to the GM production lists, the last 4107 was delivered in June, 1969. The 4108 was introduced in 1970 and produced until 1978.
Bob
What is the difference between the PD-4108 and the P8M-4108A I have a buddy that owns a P8M-4108 A
Quote from: windtrader on June 02, 2017, 12:20:30 PM
New twist to thread. Variations on the 8v71N using different injectors.
Injector size is directly proportional to the horsepower and torque the engine produces.
Researching how much one can improve performance from natural 8v71 using different injectors.
What does the busnuts say?
N55- 260hp and 680lb/ft
N60- 280hp and 740lb/ft
N65- 304hp and 800lb/ft
N70- 320hp (or 318hp if you prefer) and 860lb/ft
7G65 - Uses a different metering system, more accurate delivery, atomizes the fuel better,has better spray pattern,more adjustable ability and a higher pop pressure makes for cleaner burning better injector than the N series
A timing
N65 - Involves pulling the rear cover off (removing the trans from the engine).
N70 - Increase to 318hp and 860lb/ft torque.
Once you get higher than an N60 injectors in an original 8V71NA with standard timing, you have to change the timing to A (advanced) timing to run N65 injectors with the 304 HP. Not a good idea in the older engines with large oval air box covers that didn't cool the lower part of clyinders which resulted in cracked bores. (dry blocks vs. wet blocks in Detroit terminology).
Without changing the timing, the engines would smoke under load and acceleration. The E injectors were used with the 92 Series and as far as I know were used in CARB (CA EPA) 92 engines (the G injectors we're Federal). I know Don Fairchild did a lot of experiments with Detroit engines and has formulas with mixing this and that for increased horsepower, but I haven't heard of improved fuel mileage with his expensive changes and additions.
--Geoff
The E injector was a federal injector in the 8v71N/A,you differently no not want advanced timing with a 7E65 they smoke and are gutless.When using the 7C65,7C70 or 7C75 you retard the timing on a 8v71NA.
Detroit used the 7E65 with standard timing on the 8v71NA to raise the peak torque from 1200 rpm to 1400 rpm
Hey, I found a discrepancy in the power figures. Earlier I posted that a 8v71T has 308hp with n65 injectors 865 lbs torque. Later I posted an 8V71N with N65 has 304hp and 800lb/ft. These were cut and pasted from other posts during my research. The thread started out as a turbo question but the latest posts are questions about injector options on a Natural motor.
Is the power increase even worth the time and expense to swap out injectors on an N?
Thanks
Quote from: luvrbus on June 02, 2017, 07:44:04 PM
What is the difference between the PD-4108 and the P8M-4108A I have a buddy that owns a P8M-4108 A
Clifford,
As far as I know, no real difference until 1975, when GM began installing Integral power steering and air throttles and an early version of a split braking system with ABS.
Bob
I had to get out my Field Service Data book with the 1987 engine specs, my last post was from memory. By 1987 everybody was using the 92 Series engines and Series 60 so I was not up to date on the 71 Series injectors. In 1987, buses (most likely transits) the only 71 engine available was the 6V71. Coach listings for that year also had 6V92 and 8V92 engines. Looking under trucks, the 8V71 used 7E65 injectors for 304HP @ 2100 rpms with advanced timing. They don't show TA engines except industrial versions.
--Geoff
Quote from: TomC on May 22, 2017, 08:30:47 AM
I converted my 8V-71N to a turbo. Don Fairchild first looked at the piston rings and determined they were the tight fit rings-as compared to the looser rings that truck engines run. We kept the 18.7 to 1 pistons that were two piece (only difference between turbo and NA two piece pistons is the deck height). I added an air to air intercooler in front of the radiator (luckily had the room). But also had to increase radiator and also add misters. Increased air cleaner from 6" to 7" hose, added auxiliary transmission cooler with thermostatically controlled 12v fan, changed stuffed up muffler to turbo muffler, added by pass valve to blower, added fuel modulator. Was extensive, not cheap, but the performance is truly different. My fuel mileage is the same-mainly because we didn't change the cylinder liners or cam timing. But comparing the N65 injectors at 300hp @ 800lb/ft torque to the now 7G75 injectors at 375hp @ 1125lb/ft torque, you can see the difference in hill climbing with the torque increase. Good Luck, TomC
I had my Data book out and looked up some specs. The industrial 8V71TA with 7G65 injectors is rated at 330 HP@2100 rpms. With 7C65 injectors that same engine with the same turbo (TV8501 A/R 123) is rated at 360 HP. These engines had standard timing with 1.05 or .95 liner ports, and 17:1 compression. I'm thinking with 1.05 liners and an A/R of 105 you would get 375 HP.
--Geoff
Geoff,
What does the book show for the N motor with different injectors? Thanks
Quote from: windtrader on June 03, 2017, 09:05:43 AM
Geoff,
What does the book show for the N motor with different injectors? Thanks
8V71N
N55 injectors 265 HP @ 2100rpm
N60. 280
N65. 305
Last time I counted there was over 60 injectors for the 8v71's even 7E65's can have dozen of fuel calibrations delivery setting plus timing settings,there are so many configurations on a DD that can be done it's not funny.I like getting outside the box on DD's myself ;D,fire truck engines used N70's for the full 318 hp on the NA engines that was a factory setting fwiw
They used to call the 8V-71N with the N65's the "318" because that was the gross hp number. It got so any 8V-71 was called a 318, I think. I expect 304 is the SAE net hp number, which is a lot truer.
Quote from: bevans6 on June 03, 2017, 09:52:55 AM
They used to call the 8V-71N with the N65's the "318" because that was the gross hp number. It got so any 8V-71 was called a 318, I think. I expect 304 is the SAE net hp number, which is a lot truer.
Data shows 316 @ 2300 rpm, but It is only factory on a firetruck. I have also seen other HP ratings that have the above at 318 HP which the truckers used even though they probably had 304 HP. N70's makes adv. timed 8V71's 318HP @ 2100 rpm's, but they start smoking. The truckers always used the horsepower rating to identify their engine instead of the model. I had a trucker call me back in the early eighties and tell me he had a 450. I replied "You mean an 8V92TA with 9290 injectors?". He didn't know that but that's how we talked in the DD shop. Truckers always did the HP and maybe the model engine. I don't know how they talk these days. I think it's by engine model number but leave out the brand leaving me to guess all the time.
--Geoff
QuoteThe industrial 8V71TA with 7G65 injectors is rated at 330 HP@2100 rpms.
Quote8V-71N with the N65's the "318" because that was the gross hp number. It got so any 8V-71 was called a 318, I think. I expect 304 is the SAE net hp number, which is a lot truer.
Quotefire truck engines used N70's for the full 318 hp on the NA engines that was a factory setting
Based on these statements it seems the difference in HP between a turbo and a Natural with upgraded injectors is not so much. 318hp Natural to 330hp 8V71TA. If so, it seems like a lot of resources to upgrade to the turbo for not much hp gain. The turbo seems to make its difference known in high altitude terrain as the Natural loses a lot of steam.
When I first installed my 8V-71T ex-NATO engine it had N80 injectors and 405 gross HP. Smoked pretty decent at full throttle too. But the difference between it and the 8V-71N with 304 hp that it replaced was frankly astounding. When I drove the original engine from Toronto to Nova Scotia, the hills on the 401 were mostly third gear and 50 - 55 mph, and the hills in Quebec and New Brunswick were worse, some second gear. With the turbo engine I didn't shift down on a hill unless I was baulked by traffic. I would hit the hill at 65 mph, be doing 60 at the top and the engine would just kind of start to grunt a bit as it took up the load. Really neat.
Brian
Quote from: windtrader on June 03, 2017, 11:31:14 PM
Based on these statements it seems the difference in HP between a turbo and a Natural with upgraded injectors is not so much. 318hp Natural to 330hp 8V71TA. If so, it seems like a lot of resources to upgrade to the turbo for not much hp gain. The turbo seems to make its difference known in high altitude terrain as the Natural loses a lot of steam.
The 8V71TA can be pumped up to 375 HP. 6V92TA 400 HP, but for no smoke, 8 mpg, and long engine life 350 HP.
--Geoff
The last run of the 8v71TA truck engines were 400 HP a nice engine
Thank you all! This has been a very educational thread, at least for me, and it's much clearer the finer points of injector and timing options and the effect on hp for both natural and turbo motors.
I think the torque is more significant than HP. The seat of the pants feel of a turbo Detroit is of sustained pull throughout the power band. On my 6V92TA, that is between 1200 and 2000 rpm. Going up a hill, it seems to settle a bit and then power steadily up the hill. It takes a serious incline to have to down shift.
I noticed that same thing after I turboed the 4-71 in the Courier 96. A natural will lug and slow down until you have to down shift. After turboing, you can feel the torque pushing steadily up the hill.
JC
Quote from: lostagain on June 04, 2017, 08:49:22 PM
I think the torque is more significant than HP.
BINGO!!
;)
Quote from: RJ on June 05, 2017, 02:28:16 AM
BINGO!!
;)
To elaborate: We have to re-educate ourselves. The car marketers many decades ago latched onto horsepower numbers as a way to fool us into buying things.
A busnut needs torque to climb hills.
Pay attention to the torque number, differences here will kick you hard in the seat of the pants.
happy coaching!
buswarrior
Problem is you need a certain amount of HP to develop the torque on a diesel engine cars just need hp and rpms for speed
If you watch the TV commercials on pickup trucks they always mention the torque specs along with horsepower.
--Geoff
Yep I been looking at new pickups (friggn crazy prices) they have the 6.7 diesels up to over 400 + HP and over 900 ft lbs of torque at 1800 rpms that is more a 8v71.Ford and Chevy are battling it out in that race Dodge and Cummins are getting left in the dust.
After reading seems like the small diesels are getting 2 ft lbs of torque for each HP and the larger truck diesels are 4 ft lbs per HP
Yes that's true that there is a pickup truck horsepower/torque race going on. And those power ratings are only released from the engine computer under light load situations.
BUT-when the engines are installed in larger trucks, like the Ford F650 and F750, the power rating is restricted to 660lb/ft torque (Powerstroke 6.7). On the 6.7 Cummins when installed in a M2 Freightliner, 300hp @ 700lb/ft is the highest, and if running an Allison 2000 series, 660lb/ft torque. Good Luck, TomC
Quote from: TomC on June 05, 2017, 08:27:30 AM
Yes that's true that there is a pickup truck horsepower/torque race going on. And those power ratings are only released from the engine computer under light load situations.
BUT-when the engines are installed in larger trucks, like the Ford F650 and F750, the power rating is restricted to 660lb/ft torque (Powerstroke 6.7). On the 6.7 Cummins when installed in a M2 Freightliner, 300hp @ 700lb/ft is the highest, and if running an Allison 2000 series, 660lb/ft torque. Good Luck, TomC
That "light load"torque ratings make the commercial claims more believable. I couldn't fathom how they could get such high torque readings out of a small diesel.
--Geoff
They lower the torque and HP on those engine for another reason as the engine in heavy duty truck are always under constant torque not like a pickup,those engines would not last 60 days in truck at 440 hp and continuous torque of 910 ft lbs
The coach in question has N75 injectors and an upgraded, newer thinker rad.
Scott, not sure what coach you are referring to but I have an 8V-71T with N75 injectors in my MC-5C with a stock cooling system in what seems to be great shape, and I don't have an overheating problem. Towing 8,000 lbs in decent east coast mountains and 90 degree temps, I run below 195 degrees. So it can be done, and you can control the power you produce with either smaller injectors or a controlled right foot.
I always laugh a bit when people talk about "it's torque that counts". Power and torque are two sides of the same coin, they are exactly the same thing. They have a little thing called time between them, like the center of a cookie. Torque is like voltage, it is potential energy. Time (in this case RPM, key on the minutes) is like current, it's voltage going somewhere and doing something, it's torque being used to do work over a period of time. Power is torque times time, same as power (watts) is voltage times current. Specifically horsepower is torque times RPM/5252. The "divided by 5252" is just a fudge factor to make the units come out in HP.
Since power is what does the work (energy expended over a period of time) in an engine we tend to like it if we have a lot of power in an RPM range that is extremely useful to us. So in a bus or a big truck we like to see a lot of power very low, so we see torque peaks as low as 1200 rpm, and the engine produces a lot of power at 1200 rpm, and we feel the effect in acceleration, or climbing a hill. We call that a "torquey engine". But if we change the gearing so the same engine could produce the exact same torque at twice the RPM, we'd have twice the power to play with. What's the bottom line? In actual driving, we need the engine to produce enough power over a wide enough range of RPM so we can move the load at low speeds, accelerate briskly to high speeds, and pull hills on the highway. The part that uses the most power is the accelerate part, so we like an engine that has great torque over a wide range of RPM so it can produce a lot of power over the working RPM range.
My truck engine, in a Ford F250, produces 570 ft lbs of torque at 2,000 rpm, on a dyno somewhere. In the truck, it's completely impossible to make it produce that amount of torque. The computer backs off the torque in first gear, and in any gear higher than that full throttle results in a far higher RPM range than 2,000 RPM. That's because the computer wants the transmission to live in first gear, and in all the other gears assumes I want maximum power regardless of what the torque happens to be, and gives me the RPM range that produces maximum power, not maximum torque.
Quote from: bevans6 on June 09, 2017, 11:43:27 AM
I always laugh a bit when people talk about "it's torque that counts". Power and torque are two sides of the same coin, they are exactly the same thing. They have a little thing called time between them, like the center of a cookie. Torque is like voltage, it is potential energy. Time (in this case RPM, key on the minutes) is like current, it's voltage going somewhere and doing something, it's torque being used to do work over a period of time. Power is torque times time, same as power (watts) is voltage times current. Specifically horsepower is torque times RPM/5252. The "divided by 5252" is just a fudge factor to make the units come out in HP.
Bingo!
You have the heart of an engineer.
Its good to see that I'm not the only one laughing.
Power is rate of torque, (just a energy is rate of doing work) basically.
Just a sideline to torque-Detroits DD engines are now producing maximum torque at 975 rpm with suggested cruise speed at 1,300rpm. With the low end torque, direct drive transmissions, 2.16:1 ratio, with 517rpm tires, that would give at 65mph cruise at 1,210rpm. Also with over 14:1 starting gears, they had to go to much larger U-joints. Even the new GHG17 engines, as clean as they are, are only a tad more expensive to run (mainly because going from 3% to 4% DEF burn in relationship to fuel burn) Good Luck, TomC
It always been torque starts you moving and HP keeps you moving.I like the torque on the newer engines they are not like a older diesel that long flat torque line is the best.
Yes-the torque curve (nearly flat) is a far cry from old days of 238 and 318 Detroits, Super 250 Cummins, 1693 Cats, Maxidyne Mack.
Yep I would rather have a 400 hp producing 1600 ft lbs of torque than a 500 hp producing 1400 lbs with the long almost flat torque curve any day
Hello,
It's been awhile since I've been on here but it looks like I'll have some time to start working on my project. I have a 4107 with a transplanted 8v71TA from, what I've been told, a 77 transit. It's mated up to the 3 speed auto, not sure of the model number again. I've been told it is a rebuild and only has about 10k miles on the engine and tranny. I got the bus in the early stages of the build from the PO but he passed away. I was reading this thread the other day and looked at the injectors in my engine. Looks like they are C60's I'm pretty sure the engine is setup originally stock with the turbo. I didn't find the Aftercooler water line but I may not have been looking in the correct place. I was doing a bit of research and I couldn't find much about a turbo with C60's but it looks like the C60's aren't that common. I am looking for good performance but without sacrificing economy. I know I can't always have the best of both worlds. I think I'm leaning on economy more. But I also know that if you under power a vehicle then you will suffer economy, performance, and longevity. The PO also installed a vac/boost gauge right before the blower intake. I haven't been able to drive it much but sitting still and I rev it up I will get a vacuum on the gauge. I drove it up to the Port of entry on the 4th to weigh it and I never saw a boost on the gauge but I can hear the turbo back there and I can sure hear it spin down when I shut the engine off. So, on with the questions.....
Is the C60's ok with a turbo engine? Does it sound like they are stock. I understand the C's are California low emissions version. The engine does not smoke at all! just a small puff on startup and then clean as a whistle. Is this the setup recommended with the tranny I have? I am now running the 12 22.5 tires but I'm going to run 11 24.5's as they are about the same size, easier and cheaper to find, and the local tire shop has some used 24.5 bud aluminum rins laying around and I know them well enough they will give me the rims for buying tires from them. Anything you would suggest I change or look at?
Thanks,
Eric.
The C60's were the standard injector for turbo 8V71, but before you think of going bigger, look at your block and see if the air box covers are small rectangular covers or the big oval stamped steel covers.
If you have the big oval covers, just hold your breath. You have a "dry block" and they will crack on the lower bore. Otherwise, N75'S will work.
--Geoff